Vitamins & Supplements · Supplement formula

Fat Burners and Weight-Loss Blends

Not applicable (a product type) · also called Fat burners, diet pills, weight-loss supplements, quemadores de grasa, suplementos para bajar de peso

Fat burners and weight-loss blends are pills, capsules and teas that mix caffeine, plant extracts and other ingredients, sold to help people lose weight. Trials test single ingredients, not the finished blends, and mostly show small or no weight loss. The bigger concern is safety: liver injury, higher blood pressure and hidden prescription drugs. Many products also did not match their labels in lab tests.

General information, not medical advice. Last substantive update October 26, 2026 · Not medically reviewed. A named clinician has not signed off on this page. How this page is made

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About Fat Burners and Weight-Loss Blends

Fat burners are mixes of caffeine, plant extracts and similar ingredients sold for weight loss. Trials test the ingredients, not the mixes, and show small or no weight loss. The main concerns are liver injury, higher blood pressure and hidden drugs.

What these products are

Fat burners and weight-loss blends are pills, capsules and teas sold online and in stores. Their labels promise weight loss, fat shedding, and sometimes extra energy or performance. 'Fat burner' is a marketing term, not a medical one.

They are sold to adults who want to lose weight, including in stores and websites aimed at service members. They are not approved by the FDA before sale.

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What is usually inside

Common ingredients include caffeine, green tea extract, Garcinia (Garcinia cambogia), bitter orange (synephrine), white kidney bean, conjugated linoleic acid (CLA) and the fibre glucomannan. Chromium and berberine are also sold for weight. Most have their own page; see the related links.

Some products also hold ingredients that are not on the label. Lab tests found hidden prescription drugs in some weight-loss products.

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Reading the label

Lab studies compared the Supplement Facts panel with what was found inside. In one study of 44 products, 82% had inaccurate labels, and none showed a third-party testing seal. The FDA says 'herbal' or 'all natural' does not mean a product is safe or true to its label, and it does not approve facilities.

How a 'proprietary blend' or '% Daily Value' is defined was not read from a source for this page. Ask a pharmacist how to read a blend label, and add up the caffeine in every product you use.

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What the research shows

No trial of a finished fat-burner blend was found. A 2020 review of 54 trials found combinations of green tea, white kidney bean or ephedra gave weight differences that were not clinically significant, and no single herbal medicine could be recommended.

For single ingredients, green tea and glucomannan show small average losses, bitter orange shows none and raises blood pressure, Garcinia shows no effect, and CLA shows small changes that vanish for fat in the best trials.

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At a glance

Traditional uses history, not proof

These are modern products sold for weight loss, not a traditional remedy
Some ingredients, such as green tea, come from long-used plants

Studied for research

Weight loss from finished blends, insufficient evidence
Green tea and weight, low certainty
Bitter orange (synephrine), no weight benefit shown and higher blood pressure
Garcinia, no weight effect as a single ingredient
CLA and body fat, low certainty
Glucomannan and other single ingredients, small average losses

Main compounds

Caffeine
Green tea catechins
Hydroxycitric acid (Garcinia)
p-Synephrine (bitter orange)
Conjugated linoleic acid
Glucomannan

Common forms

Pills and capsules
Teas
Multi-ingredient blends
Products sold online and in stores

Research links: 2020 review: herbal medicines for weight loss (54 trials) · 2012 Cochrane review: green tea for weight loss · 2022 meta-analysis: bitter orange (synephrine) safety and efficacy · 2022 registry study: Garcinia cambogia liver injury · 2018 analysis: unapproved drugs in supplements named in FDA warnings · 2024 lab study: label accuracy of weight-loss supplements · Research Library · Genes & Biomarkers Library

What it is and its history

Accepted scientific name: Fat burners and weight-loss blends (multi-ingredient supplements sold for weight loss)
Common names: Fat burners (English); Weight-loss supplements (English); Thermogenic supplements (English); Diet pills (English); Quemadores de grasa (Spanish); Suplementos para bajar de peso (Spanish)
Family or group: A product type. Each product combines several ingredients, for example caffeine, plant extracts such as green tea, Garcinia, bitter orange or white kidney bean, fibres such as glucomannan, and fatty acids such as CLA. The finished mix is what the label sells; trials mostly test one ingredient.
Harvest and processing: Sold as pills, capsules and teas (FDA wording), online and in stores. Sold with claims of weight loss, fat shedding, energy and performance (2024 military label study). How the mixes are made was not read from a source.
Look-alikes and adulterants: Name: Pre-workout supplements; Note: Stimulant-heavy mixes sold for exercise; they share some ingredients. Has its own page.; Name: Fibre supplements; Note: Bulking fibres taken for fullness or bowel use. Has its own page.; Name: Prescription weight-loss medicines; Note: Approved and doctor-led; not the same as supplement products.; Name: Energy and focus formulas; Note: Often caffeine-based. Has its own page.
Sustainability and conservation: Not assessed.

What is inside, and how it may work

What it contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.

Main compounds

Compound	Family	Where it is concentrated	Activity studied	Level of evidence
Caffeine	stimulant (methylxanthine)	Not read from a source.	A common stimulant in these blends. The FDA gives a daily figure for most adults as a regulator statement. ¹³	Regulator statement
Green tea catechins	catechin polyphenols	Leaf (Camellia sinensis) Not read from a source.	Tested for weight; extract linked to uncommon liver injury. ^{6 12 16}	Human data
Hydroxycitric acid	organic acid	Fruit rind (Garcinia) Not read from a source.	The Garcinia constituent proposed to inhibit ATP-citrate lyase; proposed in a review as a route to liver damage. ¹⁹	Proposed mechanism
p-Synephrine	stimulant amine	Fruit (bitter orange) Not read from a source.	Raised blood pressure and heart rate in pooled trials; no weight-loss evidence. ⁷	Human data
Conjugated linoleic acid	fatty acid	Not read from a source.	Small body-composition changes in trials; none for fat in high-quality ones. ¹	Human data
Glucomannan	soluble fibre	Konjac root Not read from a source.	-1.36 kg versus placebo in a network review, low certainty. ⁹	Human data
Sibutramine, fluoxetine, phenolphthalein	hidden prescription or banned drugs	Found as undeclared additions in lab tests; not ingredients.	Not on labels. Sibutramine was in most FDA-warned weight-loss products. ^{10 5}	Laboratory analysis

Mechanisms, receptors and pathways

Target or pathway	Gene or receptor	What was found	Level
Raised energy use (claimed)	Not specified in the sources read	The Cochrane review says catechins and caffeine are each believed to raise energy use. Pooled trials did not show this gave a meaningful weight loss. ⁶	Human data
Immune reaction in Garcinia and green tea liver injury	HLA-B*35:01	This gene variant was found in 55% of Garcinia liver-injury patients versus 19% of those with other supplement injury, suggesting an immune-mediated route. ¹¹	Human data
Hydroxycitric acid and liver cells	ATP-citrate lyase	A 2025 review proposes oxidative stress, inflammation and cell death caused by hydroxycitric acid inhibiting this enzyme. Proposed, not proven in people. ¹⁹	Proposed
Cardiovascular stimulation by synephrine	Not specified	Blood pressure and heart rate rose in pooled trials. ⁷	Human data

Absorption, metabolism and elimination

Absorption: Not found for finished blends.
Distribution: Not found.
Metabolism: Not found.
Elimination: Not found.
Bioavailability: Not compared across products in the sources read.

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Isolated compounds versus whole extracts

Trials test single ingredients, not the mixes sold. Adding up single-ingredient results does not tell what a mix does; combinations can also add hidden stimulants or drugs. Green tea as a drink had no reported safety concerns in adults, but extract supplements have caused uncommon liver injury.

Nutritional composition

These products are not foods and have no meaningful nutrient content. Caffeine in tea or coffee is a different exposure from caffeine pills; the FDA gives one total for all sources.

6benefits and uses looked at

19studies and sources checked

Low certaintybest evidence rating found

4lab markers tracked in trials

5 low certainty1 not enough evidence

What was looked at

The 6 benefits and uses checked for Fat Burners and Weight-Loss Blends, each with how strong the evidence is. Tap one to open it.

Weight loss from finished fat-burner blendsNot enough evidence
Green tea and body weightLow certainty
Bitter orange (synephrine) and weightLow certainty
Garcinia (Garcinia cambogia) and weightLow certainty
Conjugated linoleic acid (CLA) and body fatLow certainty
Fibre-type and other single ingredients (glucomannan, psyllium and others)Low certainty

Lab markers tracked in the studies

Body weightWaist circumferenceBlood pressure and heart rateFat mass and body fat percentage

What is Fat Burners and Weight-Loss Blends good for?

What research on this product type found. No trial tested a finished blend as sold, so each result below is for a single ingredient or a small combination. Single-ingredient results are not added together as if the mix was tested.

Weight loss from finished fat-burner blendsNot enough evidenceNo trial of a finished fat-burner blend, as sold on shelves, was found in the sources read. What exists are trials of single plant ingredients and of a few combination preparations. In a 2020 review of 54 placebo-controlled trials, combinations containing green tea, white kidney bean or ephedra changed weight by amounts that were statistically real but not large enough to matter in daily life. The reviewers found too little evidence to recommend any herbal medicine for weight loss. Green tea and body weightLow certaintyGreen tea is the most common single ingredient in these blends. A Cochrane review of 14 trials lasting 12 to 13 weeks found a small weight change that was not statistically significant and unlikely to matter. Outside Japan the pooled difference was 0.04 kg. A 2023 network review found a larger average loss of 1.25 kg, with low certainty. A 2020 review found no effect for green tea as a single agent. Bitter orange (synephrine) and weightLow certaintyA 2022 meta-analysis of 18 placebo-controlled trials found no significant weight loss after prolonged use and no change in body composition. Blood pressure rose: 6.37 mmHg for the top number and 4.33 mmHg for the bottom number. The authors say synephrine tends to raise blood pressure and heart rate. Garcinia (Garcinia cambogia) and weightLow certaintyIn the 2020 review of 54 trials, Garcinia cambogia as a single agent had no effect on weight compared with placebo. Its main report in the research is liver injury, not weight loss. Conjugated linoleic acid (CLA) and body fatLow certaintyA 2024 meta-analysis of 70 trials (4,159 people) found small drops in body weight and fat mass. In the highest-quality trials, fat mass and body fat percentage did not change. The authors say the weight effect was small and may not matter clinically. Fibre-type and other single ingredients (glucomannan, psyllium and others)Low certaintyA 2023 network review of 111 trials found small average weight losses for several single ingredients. Glucomannan was 1.36 kg with low certainty. Psyllium was 3.70 kg, chitosan 1.70 kg, Nigella sativa 2.09 kg and curcumin 0.82 kg, all with moderate certainty. Spirulina was 1.77 kg with high certainty. These are single ingredients, not stimulant fat-burner blends.

Benefits, one by one

Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.

Weight loss from finished fat-burner blends

Not enough evidence

No trial of a finished fat-burner blend, as sold on shelves, was found in the sources read. What exists are trials of single plant ingredients and of a few combination preparations. In a 2020 review of 54 placebo-controlled trials, combinations containing green tea, white kidney bean or ephedra changed weight by amounts that were statistically real but not large enough to matter in daily life. The reviewers found too little evidence to recommend any herbal medicine for weight loss.

2 studiesCombination preparations in the review contained green tea, white kid…

Studies, doses and limits

What the trials found

The 2020 review pooled placebo-controlled trials in healthy overweight or obese adults, most lasting 12 weeks or less. The review counted a loss of 2.5 kg or more as clinically significant. Combination preparations did not reach that line. Herbs tested in only a few trials sometimes showed bigger losses, but the reviewers say those trials were few and poor in quality. A 2023 network review of 111 trials compared single nutraceuticals and also did not test blends.

Results

No trial of a finished blend as sold was found. Combination preparations gave small weight differences that were not clinically significant.

Effect sizes as reported

Threshold used: 2.5 kg. Combinations: statistically but not clinically significant. Amounts per trial are not given in the abstract.

Why this rating

Insufficient because the finished products were not tested, the combinations that were tested gave small differences, and many trials were short and poorly reported.

Form and dose studied

Combination preparations in the review contained green tea, white kidney bean or ephedra. Amounts vary by trial and are not stated here.

Who was studied

Healthy overweight or obese adults.

Limits

Short trials, poor reporting, and no testing of the blends people actually buy.

Why researchers looked

Blends mix several ingredients that are each said to raise energy use or cut appetite, so researchers have tested the ingredients, and sometimes small combinations, against placebo.

Traditional use

Weight-loss and fat-burner blends are sold products, not a traditional remedy. The studies below test their single ingredients, not the finished blends as sold.

Proposed mechanism Not established

Not established for finished blends. Single ingredients are said to raise energy use or block fat or carbohydrate uptake, but the sources read do not show this happens in people at a level that matters.

A proposed mechanism does not show that the effect happens in people.

Most herbs looked safe in short trials, but trials do not catch rare serious harm. See the Safety tab for liver injury and hidden drugs.

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Green tea and body weight

Low certainty

Green tea is the most common single ingredient in these blends. A Cochrane review of 14 trials lasting 12 to 13 weeks found a small weight change that was not statistically significant and unlikely to matter. Outside Japan the pooled difference was 0.04 kg. A 2023 network review found a larger average loss of 1.25 kg, with low certainty. A 2020 review found no effect for green tea as a single agent.

3 studiesGreen tea preparations of various kinds; amounts differ by trial and …

Studies, doses and limits

What the trials found

Cochrane 2012: six trials outside Japan (532 people) pooled to -0.04 kg (95% CI -0.5 to 0.4); eight Japanese trials (1,030 people) ranged from -0.2 to -3.5 kg and could not be pooled. Two trials on keeping weight off showed no clear effect. The 2023 network review put green tea at -1.25 kg (95% CI -1.68 to -0.82), low certainty. The 2020 review found no effect of green tea as a single agent.

Results

Mixed and small. The average difference is between zero and about 1.25 kg, which the Cochrane authors call unlikely to be clinically important.

Effect sizes as reported

Cochrane outside Japan: -0.04 kg (CI -0.5 to 0.4). Network review: -1.25 kg (CI -1.68 to -0.82), low certainty.

Why this rating

Low because results differ between reviews, trials were short, the Japanese trials could not be pooled, and the network review itself rates the evidence low.

Form and dose studied

Green tea preparations of various kinds; amounts differ by trial and are not stated here. Drinking tea and taking concentrated extract are not the same thing.

Who was studied

Overweight or obese adults.

Limits

Cochrane search ended in 2011. Short trials. Different products across trials.

Why researchers looked

Green tea contains catechins and caffeine, which are believed to raise energy use, so many weight trials have tested it.

Traditional use

Weight-loss and fat-burner blends are sold products, not a traditional remedy. The studies below test their single ingredients, not the finished blends as sold.

Proposed mechanism Preliminary mechanism

Not established. The Cochrane authors say catechins and caffeine are each believed to raise energy use; this was not shown to produce meaningful weight loss.

A proposed mechanism does not show that the effect happens in people.

Concentrated green tea extract in pills has been linked to uncommon liver injury. See the Safety tab.

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Bitter orange (synephrine) and weight

Low certainty

A 2022 meta-analysis of 18 placebo-controlled trials found no significant weight loss after prolonged use and no change in body composition. Blood pressure rose: 6.37 mmHg for the top number and 4.33 mmHg for the bottom number. The authors say synephrine tends to raise blood pressure and heart rate.

1 studiesBitter orange extract or p-synephrine; amounts vary by trial.

Studies, doses and limits

What the trials found

18 articles of placebo-controlled trials were pooled. After prolonged treatment weight loss was not significant and body composition did not change. Systolic pressure +6.37 mmHg (CI 1.02 to 11.72) and diastolic +4.33 mmHg (CI 0.48 to 8.18).

Results

No weight-loss benefit shown; blood pressure rose.

Effect sizes as reported

Systolic +6.37 mmHg; diastolic +4.33 mmHg; weight not significant.

Why this rating

Low because the trials were small, often used synephrine with other ingredients, and the authors call for more studies. The blood pressure rise is a pooled trial result; the lack of a weight benefit is the finding, not proof of no effect.

Form and dose studied

Bitter orange extract or p-synephrine; amounts vary by trial.

Who was studied

Adults in short trials.

Limits

Small trials. Mixed products. Long-term safety unknown.

Why researchers looked

Synephrine is a stimulant found in bitter orange. It replaced ephedra in many products, so researchers asked whether it helps weight loss.

Traditional use

Weight-loss and fat-burner blends are sold products, not a traditional remedy. The studies below test their single ingredients, not the finished blends as sold.

Proposed mechanism Preliminary mechanism

Not established for weight loss. The meta-analysis shows it raises blood pressure and heart rate.

A proposed mechanism does not show that the effect happens in people.

Raises blood pressure and heart rate in pooled trials. See the Safety tab.

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Garcinia (Garcinia cambogia) and weight

Low certainty

In the 2020 review of 54 trials, Garcinia cambogia as a single agent had no effect on weight compared with placebo. Its main report in the research is liver injury, not weight loss.

2 studiesFruit extract; amounts vary by trial.

Studies, doses and limits

What the trials found

The 2020 review found no effect of Garcinia cambogia versus placebo. It did not report a number in the abstract.

Results

No weight effect as a single agent.

Effect sizes as reported

No effect; no numbers in the abstract.

Why this rating

Low because it rests on one review's abstract and short trials.

Form and dose studied

Fruit extract; amounts vary by trial.

Who was studied

Healthy overweight or obese adults.

Limits

Short trials, abstract only.

Why researchers looked

Garcinia fruit contains hydroxycitric acid, which is marketed as a fat blocker and appetite aid.

Traditional use

Weight-loss and fat-burner blends are sold products, not a traditional remedy. The studies below test their single ingredients, not the finished blends as sold.

Proposed mechanism Preliminary mechanism

Not established for weight. The 2025 liver review lists hydroxycitric acid as inhibiting an enzyme (ATP-citrate lyase) and proposes this as a possible route to liver damage.

A proposed mechanism does not show that the effect happens in people.

More than 200 liver-injury events are linked to Garcinia products. See the Safety tab.

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Conjugated linoleic acid (CLA) and body fat

Low certainty

A 2024 meta-analysis of 70 trials (4,159 people) found small drops in body weight and fat mass. In the highest-quality trials, fat mass and body fat percentage did not change. The authors say the weight effect was small and may not matter clinically.

1 studiesCLA supplements; amounts analysed in the review but not stated here.

Studies, doses and limits

What the trials found

Body mass WMD -0.35 (CI -0.54 to -0.15), BMI -0.15, waist -0.62, fat mass -0.44, body fat -0.77%, fat-free mass +0.27. The abstract does not give units for most values. High-quality trials: no change in fat mass or body fat percentage.

Results

Small changes that shrink in better-quality trials.

Effect sizes as reported

Body mass WMD -0.35; fat mass WMD -0.44; body fat -0.77%.

Why this rating

Low because effects are small and disappear for fat measures in the best trials.

Form and dose studied

CLA supplements; amounts analysed in the review but not stated here.

Who was studied

Adults.

Limits

Abstract does not give units; trials vary.

Why researchers looked

CLA is a fatty acid sold as a fat-loss aid, alone and inside blends.

Traditional use

Weight-loss and fat-burner blends are sold products, not a traditional remedy. The studies below test their single ingredients, not the finished blends as sold.

Proposed mechanism Not established

Not established in the sources read.

A proposed mechanism does not show that the effect happens in people.

No safety signal reported in the abstract.

Fibre-type and other single ingredients (glucomannan, psyllium and others)

Low certainty

A 2023 network review of 111 trials found small average weight losses for several single ingredients. Glucomannan was 1.36 kg with low certainty. Psyllium was 3.70 kg, chitosan 1.70 kg, Nigella sativa 2.09 kg and curcumin 0.82 kg, all with moderate certainty. Spirulina was 1.77 kg with high certainty. These are single ingredients, not stimulant fat-burner blends.

1 studiesSupplements; amounts vary by trial.

Studies, doses and limits

What the trials found

The network analysis ranked 18 nutraceuticals in 6,171 adults with overweight or obesity. Values are mean weight differences versus placebo with 95% intervals, for example glucomannan -2.17 to -0.54 kg.

Results

Small average losses, rated from low to high certainty depending on the ingredient.

Effect sizes as reported

Glucomannan -1.36 kg; psyllium -3.70 kg; spirulina -1.77 kg.

Why this rating

Low for glucomannan (the only fibre-type ingredient here that blends often list) because the review rates it low; the authors rate some other single ingredients higher.

Form and dose studied

Supplements; amounts vary by trial.

Who was studied

Adults with overweight or obesity.

Limits

Single ingredients; no blends tested; trials differ in length.

Why researchers looked

Fibres and other ingredients are added to blends to make people feel full or to block fat uptake.

Traditional use

Weight-loss and fat-burner blends are sold products, not a traditional remedy. The studies below test their single ingredients, not the finished blends as sold.

Proposed mechanism Not established

Not established in the sources read.

A proposed mechanism does not show that the effect happens in people.

Not covered in the abstract.

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Connections to the rest of health

How Fat Burners and Weight-Loss Blends connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.

Explore every connection: goals, body systems, organs, symptoms, genes

Kind of connection Connected to Search

A. Wellness goals

Connected to	Evidence status	Context	Studies
Weight Management	Not enough evidence	Weight loss from finished fat-burner blends: No trial of a finished fat-burner blend, as sold on shelves, was found in the sources read. What exists are trials of single plant ingredients and of a few combination preparations. In a 2020 review of 54 placebo-controlled trials, combinations containing green tea, white kidney bean or ephedra changed weight by amounts that were statistically real but not large enough to matter in daily life. The reviewers found too little evidence to recommend any herbal medicine for weight loss.	^{8 9}
Weight Management	Low certainty	Green tea and body weight: Green tea is the most common single ingredient in these blends. A Cochrane review of 14 trials lasting 12 to 13 weeks found a small weight change that was not statistically significant and unlikely to matter. Outside Japan the pooled difference was 0.04 kg. A 2023 network review found a larger average loss of 1.25 kg, with low certainty. A 2020 review found no effect for green tea as a single agent.	^{6 9 8}
Weight Management	Low certainty	Bitter orange (synephrine) and weight: A 2022 meta-analysis of 18 placebo-controlled trials found no significant weight loss after prolonged use and no change in body composition. Blood pressure rose: 6.37 mmHg for the top number and 4.33 mmHg for the bottom number. The authors say synephrine tends to raise blood pressure and heart rate. Garcinia (Garcinia cambogia) and weight: In the 2020 review of 54 trials, Garcinia cambogia as a single agent had no effect on weight compared with placebo. Its main report in the research is liver injury, not weight loss.	^{7 8 19 1 9}

B. Body systems

Connected to	Kind of connection	Evidence status	Context	Studies
Metabolism Weight	Biological association	Not enough evidence	Studied for: Weight loss from finished fat-burner blends Studied for: Green tea and body weight	^{8 9 6 7 19 1}
Cardiovascular System	Biological association	Low certainty	Studied for: Bitter orange (synephrine) and weight	⁷

E. Health conditions

Connected to	Kind of connection	Evidence status	Context	Studies
Supplement-related liver injury	Adverse effect or risk	Case report	Garcinia and green tea extract products were linked to liver injury in registry case series. Preparation or compound: Garcinia and green tea products	^{11 12}
Obesity		Preliminary	Single ingredients show small average weight changes; finished blends were not tested. Preparation or compound: Single ingredients	^{8 9}

I. Biomarkers

Connected to	Kind of connection	Evidence status	Context	Studies
Body weight	Biological association	Low certainty	Measured in trials: small or no loss in the trials reviewed. A lab change is not the same as a health benefit.	^{6 8 9}
Waist circumference	Biological association	Low certainty	Measured in trials: no clear change outside Japan; mixed in Japanese trials. A lab change is not the same as a health benefit.	⁶
Blood pressure and heart rate	Biological association	Low certainty	Measured in trials: rose with bitter orange (synephrine). A lab change is not the same as a health benefit.	⁷
Fat mass and body fat percentage	Biological association	Low certainty	Measured in trials: small drop overall; no change in high-quality CLA trials. A lab change is not the same as a health benefit.	¹

J. Genes, receptors and enzymes

Connected to	Kind of connection	Evidence status	Context	Studies
*HLA-B35:01**	Preliminary mechanism	Human	Gene variant more common in Garcinia liver-injury patients (55% vs 19%).	¹¹

L. Active compounds

Connected to	Kind of connection	Evidence status	Context	Studies
Caffeine	Biological association	Regulator statement	A common stimulant in these blends. The FDA gives a daily figure for most adults as a regulator statement.	¹³
Green tea catechins	Biological association	Human	Tested for weight; extract linked to uncommon liver injury. Preparation or compound: Leaf (Camellia sinensis)	^{6 12 16}
Hydroxycitric acid	Biological association	Proposed mechanism	The Garcinia constituent proposed to inhibit ATP-citrate lyase; proposed in a review as a route to liver damage. Preparation or compound: Fruit rind (Garcinia)	¹⁹
p-Synephrine	Biological association	Human	Raised blood pressure and heart rate in pooled trials; no weight-loss evidence. Preparation or compound: Fruit (bitter orange)	⁷
Conjugated linoleic acid	Biological association	Human	Small body-composition changes in trials; none for fat in high-quality ones.	¹
Glucomannan	Biological association	Human	-1.36 kg versus placebo in a network review, low certainty. Preparation or compound: Konjac root	⁹
Sibutramine, fluoxetine, phenolphthalein	Biological association	Laboratory analysis	Not on labels. Sibutramine was in most FDA-warned weight-loss products.	^{10 5}

Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 26, 2026).

Evidence at a glance: what the research found for 6 outcomes

5Low certainty

1Not enough evidence

Each outcome below is one thing researchers measured. Certainty is how far the evidence can be trusted, not how well it works. The full studies are on the next tab.

Weight loss from finished fat-burner blends 2 studies Not enough evidence Green tea and body weight 3 studies Low certainty Bitter orange (synephrine) and weight 1 study Low certainty Garcinia (Garcinia cambogia) and weight 2 studies Low certainty Conjugated linoleic acid (CLA) and body fat 1 study Low certainty Fibre-type and other single ingredients (glucomannan, psyllium and others) 1 study Low certainty

The evidence

The research centre for Fat Burners and Weight-Loss Blends. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.

Evidence by outcome

Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).

How we rate evidence

High certainty

Several well-run trials or reviews agree; further research is unlikely to change the picture much.

Moderate certainty

Good trials point the same way, but some doubt remains.

Low certainty

Small, short or inconsistent trials. The finding could change with better research.

Very low certainty

Very little or very weak human data. Treat as a possibility only.

Mixed findings

Trials or reviews disagree with each other.

Not enough evidence

Not enough human research to say either way.

Evidence against

Good research found no benefit, or found harm.

We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We started from our existing page on this product type, then re-read PubMed abstracts for every review, trial, case series and lab study cited, and opened the FDA and NCCIH pages. Only abstracts were read, not full texts. The NIH Office of Dietary Supplements page was blocked and is marked unverified.

Study library: every study we checked 19

Design Research type Year from Search

Study	Design	People	Product, dose, length	Result
Asbaghi 2024 The effects of conjugated linoleic acid supplementation on anthropometrics and body composition indices in adults: a systematic review and dose-response meta-analysis. Br J Nutr · PMID 37671495 · DOI	Systematic review meta analysis	4159 70 randomised trials (96 effect sizes) in adults	Conjugated linoleic acid (CLA) supplements Supplement Varied by trial; analysed for dose-response Varied · vs Placebo or control	CLA gave small improvements: body mass WMD -0.35 (95% CI -0.54 to -0.15), BMI -0.15, waist -0.62, fat mass -0.44, body fat -0.77%, fat-free mass +0.27. In the high-quality trials, fat mass and body fat percentage did not change. The authors say the weight-loss effect was small and may not reach clinical importance. Body mass WMD -0.35; fat mass WMD -0.44; body fat -0.77% (Body mass -0.54 to -0.15; fat mass -0.66 to -0.23; body fat -1.09 to -0.45) Methods, limits and funding Outcomes: Body mass, BMI, waist, fat mass, body fat percentage, fat-free mass Limitations: The abstract does not give units for most values. Effects shrink in higher-quality trials. Heterogeneity between trials. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
Chatham-Stephens 2017 Hepatotoxicity associated with weight loss or sports dietary supplements, including OxyELITE Pro - United States, 2013. Drug Test Anal · PMID 27367536 · DOI	Outbreak investigation case series	40 40 adults in 23 US states and two military bases with acute hepatitis of unknown cause after a weight-loss or muscle-building supplement	Weight-loss or muscle-building dietary supplements; 25 patients named one multi-ingredient weight-loss product Cases from April to December 2013	25 of 40 (62.5%) reported taking one named weight-loss and sports product. Of those, 17 of 22 with data (77.3%) were hospitalised and 1 had a liver transplant. Symptoms included jaundice, fatigue and dark urine. 25 of 40 cases linked to one product; 77.3% of those with data hospitalised (Not applicable) Methods, limits and funding Outcomes: Acute hepatitis, hospitalisation, liver transplant Limitations: Case-finding from poison-centre and FDA reports, so it misses unreported cases. Cannot give a risk rate. The exact ingredient that caused harm is not settled by this report. Funding and conflicts: US government authors (CDC, FDA, Department of Defense); no outside funding stated in the abstract. Read: abstract
Crawford 2024 Label Accuracy and Quality of Select Weight-Loss Dietary Supplements Sold on or near US Military Bases. Nutrients · PMID 39770990 · DOI	Laboratory case series	44 44 weight-loss supplements bought in stores on or near 12 US military installations, March 2023 to January 2024	Weight-loss dietary supplements Capsules and similar	36 of 44 (82%) had inaccurate labels. 27 (61%) listed ingredients that were not detected. 16 (36%) had hidden ingredients. 40 (91%) scored 'no-go' on the risk scorecard and none carried a third-party certification seal. Many products held several stimulants, so their safety was unknown. 36 of 44 (82%) inaccurate; 16 (36%) with hidden ingredients (Not applicable) Methods, limits and funding Outcomes: Label accuracy, hidden ingredients, prohibited ingredients, label claims Limitations: Select products from military-area stores; not all US stores. Funding and conflicts: Conflict of interest: none relevant reported. Read: abstract
Crawford 2024 Label Accuracy of Weight Loss Dietary Supplements Marketed Online With Military Discounts. JAMA Netw Open · PMID 38691359 · DOI	Laboratory case series	30 30 weight-loss supplement products bought online in June 2023 from 12 companies advertising military discounts	Weight-loss dietary supplements Capsules and similar	25 of 30 had inaccurate labels. 24 listed ingredients that were not detected. 7 had hidden components not on the label, some that would count as adulterated. 10 held substances on the US military prohibited list, listed or hidden. All 30 were rated risky on a risk scorecard. 25 of 30 inaccurate; 7 with hidden components (Not applicable) Methods, limits and funding Outcomes: Whether contents matched the Supplement Facts label; prohibited ingredients Limitations: A selected set of 30 products from one marketing channel; not a market survey. Funding and conflicts: Conflict of interest: none reported. Authors are at a US military university and a university natural-products centre. Read: abstract
Jairoun 2021 Adulteration of Weight Loss Supplements by the Illegal Addition of Synthetic Pharmaceuticals. Molecules · PMID 34833995 · DOI	Laboratory analysis of products	137 137 herbal weight-loss supplements bought for sale in the United Arab Emirates	Herbal weight-loss supplements tested for sibutramine, phenolphthalein and fluoxetine	15.3% contained undeclared sibutramine, 13.9% undeclared phenolphthalein and 5.1% undeclared fluoxetine. Overall 17.5% held significant amounts of at least one of the three. The authors note that people who take several supplements a day may get high combined exposure. 17.5% (24 of 137) with at least one undeclared drug (Sibutramine 15.3% (9.2-21.4); phenolphthalein 13.9% (8.01-19.7); fluoxetine 5.1% (1.4-8.8)) Methods, limits and funding Outcomes: Presence of undeclared drugs Limitations: One country, one set of products, three drugs tested. Not a measure of other markets. Funding and conflicts: Conflict of interest: none declared. Read: abstract
Jurgens 2012 Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database Syst Rev · PMID 23235664 · DOI	Systematic review meta analysis	1562 Overweight or obese adults; 6 trials outside Japan (532 people pooled) and 8 trials in Japan (1,030 people, not pooled)	Green tea preparations taken by mouth Preparations varied Varied by trial; amounts not stated in the abstract 12 to 13 weeks · vs Control (placebo or no green tea)	Outside Japan, pooled weight change was -0.04 kg versus control. Japanese trials ranged from -0.2 kg to -3.5 kg and were not pooled. The authors judged the loss small, not statistically significant and unlikely to matter clinically. No effect on keeping weight off. Of 8 trials that recorded side effects, 2 reported an event needing hospital care (reported as not linked to the tea). Mean difference in weight -0.04 kg outside Japan; BMI -0.2 kg/m2; waist -0.2 cm (Weight 95% CI -0.5 to 0.4 kg; BMI -0.5 to 0.1; waist -1.4 to 0.9 cm) Methods, limits and funding Outcomes: Weight, body mass index, waist circumference, weight maintenance, adverse events Limitations: Search ended in 2011, so newer trials are missing. Trials were short (12 to 13 weeks). Japanese and non-Japanese trials differed too much to pool. Funding and conflicts: Conflict of interest: none known. Read: abstract
Koncz 2022 The Safety and Efficacy of Citrus aurantium (Bitter Orange) Extracts and p-Synephrine: A Systematic Review and Meta-Analysis. Nutrients · PMID 36235672 · DOI	Systematic review meta analysis	18 placebo-controlled human trials of synephrine	Bitter orange (Citrus aurantium) extract or p-synephrine by mouth Extract or isolated compound Varied by trial Short and prolonged use compared · vs Placebo	After prolonged use, systolic blood pressure rose 6.37 mmHg and diastolic 4.33 mmHg versus placebo. Weight loss after prolonged treatment was not significant and body composition did not change. Synephrine tends to raise blood pressure and heart rate, and the authors found no evidence that it helps weight loss. Systolic +6.37 mmHg; diastolic +4.33 mmHg (Systolic 1.02 to 11.72; diastolic 0.48 to 8.18) Methods, limits and funding Outcomes: Weight, body composition, blood pressure, heart rate Limitations: Trials were small and many gave synephrine with other ingredients. Long-term safety not covered. Funding and conflicts: Conflict of interest: none declared. Read: abstract
Maunder 2020 Effectiveness of herbal medicines for weight loss: A systematic review and meta-analysis of randomized controlled trials. Diabetes Obes Metab · PMID 31984610 · DOI	Systematic review meta analysis	54 placebo-controlled trials in healthy overweight or obese adults	Herbal medicines for weight loss, alone and in combination preparations Plant extracts (forms varied) Varied by trial Commonly 12 weeks or less · vs Placebo	As single agents, only white kidney bean (Phaseolus vulgaris) gave a statistically significant weight loss, and it was not clinically significant. No effect for green tea (Camellia sinensis) or Garcinia cambogia. Combination preparations containing green tea, white kidney bean or ephedra gave statistically but not clinically significant differences. Herbs tested in 3 or fewer trials sometimes showed larger losses, but the authors say to read these cautiously (few, poor-quality trials). Most herbs appeared safe over the short trials. Conclusion: not enough evidence to recommend any herbal medicine for weight loss. No single agent reached 2.5 kg except small, poor-quality trials (Not given in the abstract) Methods, limits and funding Outcomes: Body weight (a difference of 2.5 kg or more was counted as clinically significant) Limitations: Short trials. Poor methods and reporting in many small trials. Safety over the long term not covered. Funding and conflicts: Conflict of interest not stated in the abstract. Read: abstract
Shahinfar 2023 Comparative effects of nutraceuticals on body weight in adults with overweight or obesity: A systematic review and network meta-analysis of 111 randomized clinical trials. Pharmacol Res · PMID 37778464 · DOI	Network meta analysis	6171 111 randomised trials of 18 nutraceuticals in adults with overweight or obesity	Single nutraceuticals (for example green tea, glucomannan, psyllium, chitosan, curcumin, spirulina, Nigella sativa) Supplements Varied by trial Varied · vs Placebo or another nutraceutical	Weight differences versus placebo: spirulina -1.77 kg (high certainty), psyllium -3.70 kg, Nigella sativa -2.09 kg, chitosan -1.70 kg and curcumin -0.82 kg (all moderate certainty), green tea -1.25 kg and glucomannan -1.36 kg (both low certainty). The authors conclude nutraceuticals can give a small weight loss. Green tea -1.25 kg; glucomannan -1.36 kg; psyllium -3.70 kg (Green tea -1.68 to -0.82; glucomannan -2.17 to -0.54; psyllium -5.18 to -2.22) Methods, limits and funding Outcomes: Body weight in kg Limitations: Trials differ in length and product. Single ingredients only; no blends were tested as sold. Funding and conflicts: Conflict of interest: none declared. Read: abstract
Tucker 2018 Unapproved Pharmaceutical Ingredients Included in Dietary Supplements Associated With US Food and Drug Administration Warnings. JAMA Netw Open · PMID 30646238 · DOI	Analysis of regulator database	776 776 adulterated dietary supplements named in FDA warnings from 2007 through 2016	Products sold as dietary supplements that contained unapproved drug ingredients 2007 to 2016	317 of the 776 (40.9%) were marketed for weight loss. The hidden drug in 269 of those 317 (84.9%) was sibutramine. 157 products (20.2%) held more than one unapproved ingredient. Of 28 products named in 2 or 3 warnings more than 6 months apart, 19 (67.9%) had new unapproved ingredients the second or third time. In 2014 to 2016, 38.6% were found by online sampling and 34.3% in international mail. Weight loss: 317 of 776 warnings; sibutramine in 84.9% of them (Not applicable) Methods, limits and funding Outcomes: Types of hidden ingredients by product category Limitations: Counts warnings the FDA chose to issue, not how common adulteration is across the whole market. An erratum was published in 2018. Funding and conflicts: Conflict of interest: none reported. Read: abstract
Vuppalanchi 2022 Garcinia cambogia, Either Alone or in Combination With Green Tea, Causes Moderate to Severe Liver Injury. Clin Gastroenterol Hepatol · PMID 34400337 · DOI	Prospective registry case series	22 22 patients with liver injury adjudicated as due to Garcinia cambogia (5 alone, 16 with green tea, 1 with ashwagandha), from 1,418 enrolled in the US Drug-Induced Liver Injury Network	Garcinia cambogia products, alone or combined Supplements Liver injury began 13 to 223 days after starting (median 51) · vs Control groups of 57 green-tea-supplement cases and 103 other supplement cases	Ages 17 to 54. One patient died, one needed a liver transplant and 91% were hospitalised. Injury was hepatocellular with jaundice. The HLA-B35:01 variant was found in 55% of the Garcinia group versus 19% of other supplement cases. The authors say injury from Garcinia and green tea is clinically indistinguishable. 22 high-confidence cases; 1 death; 1 transplant; 91% hospitalised (Not applicable) Methods, limits and funding Outcomes:* Liver injury severity, outcome, HLA-B35:01 gene variant Limitations:* Cases only: no rate of harm in users. Most cases involved a combination product. Funding and conflicts: PubMed lists US NIH research support (extramural and intramural); no company funding stated in the abstract. Read: abstract
Zheng 2016 Risk of Liver Injury Associated with Green Tea Extract in SLIMQUICK Weight Loss Products: Results from the DILIN Prospective Study. Drug Saf · PMID 27189593 · DOI	Prospective registry case series	6 6 women aged 22 to 58 with liver injury attributed to one family of weight-loss products, out of 1,091 liver-injury cases enrolled 2007 to 2011	Weight-loss products listing green tea extract or catechins in 5 of 6 cases Supplements	All six had hepatocellular injury with ALT above 1,000 U/L in all but one. Three were hospitalised, one had a successful liver transplant and none died. The authors say green tea extract should be studied as a possible cause. 6 of 1,091 cases; 1 transplant (Not applicable) Methods, limits and funding Outcomes: Liver enzymes, hospitalisation, transplant Limitations: Six cases. The product mix contained several ingredients, so the cause is not proven. Funding and conflicts: PubMed lists US NIH research support; no company funding stated in the abstract. Read: abstract
s-fda-caffeine US FDA: Spilling the Beans: How Much Caffeine Is Too Much? · Source	Regulator page n/a			Methods, limits and funding Read: page
s-fda-hidden US FDA: Avoiding Products Contaminated with Hidden Ingredients · Source	Regulator page n/a			Methods, limits and funding Read: page
s-fda-weight-loss US FDA: Weight Loss Product Notifications (Medication Health Fraud) · Source	Regulator page n/a			Methods, limits and funding Read: page
s-nccih-green-tea NCCIH (US): Green Tea · Source	Regulator page n/a			Methods, limits and funding Read: page
s-ods-weight NIH Office of Dietary Supplements: weight-loss fact sheet · Source	Reference database n/a			Methods, limits and funding Read: not-read
s-site-summary Existing AlternativeMed page for this formula type (read 2026-10-26)	Internal summary n/a			Methods, limits and funding Read: summary-only
van Breemen 2025 Hepatotoxicity of dietary supplements containing Garcinia gummi-gutta (L.) N. Robson. Pharm Biol · PMID 41262061 · DOI	Review of case reports	34 More than 200 liver-injury adverse events in databases; 34 published case reports reviewed	Garcinia (Garcinia cambogia, Garcinia gummi-gutta) fruit-extract supplements Dietary supplements	More than 200 liver-injury events were found. Among 34 case reports there was one death and nine liver transplants. 17 cases scored possible to highly probable for causality, and in one case liver injury returned on re-use (rechallenge). The pattern fits drug-induced liver injury. Proposed mechanisms include an immune reaction linked to the HLA-B35:01 gene variant, oxidative stress and cell death caused by hydroxycitric acid. 1 death and 9 transplants among 34 case reports (Not applicable) Methods, limits and funding Outcomes:* Liver injury, liver transplant, death Limitations: Case reports cannot give a rate of harm. Reports often involve multi-ingredient products. Funding and conflicts: Authors include staff of Procter & Gamble Healthcare and USP-India; the paper states no conflict of interest. Read: abstract

What we do not know yet

No trial of a finished fat-burner blend as sold was found.
Trials of single ingredients are short, mostly 12 weeks or less.
The NIH Office of Dietary Supplements fact sheet could not be read.
No interaction studies of finished blends were found.
No pregnancy, breastfeeding or children safety trials were found.
Metals and other contaminants in these products were not researched.
The definition of 'proprietary blend' was not read from a source.

How new research is added

New studies are found by a saved PubMed search and placed in a review queue before the page changes.

Lab markers

What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".

Metabolic 1

●

Body weight

Small or no loss in the trials reviewed in trials

Weight in kilograms, measured on a scale in a trial before and after the product.

Low certainty

Results and what it means

Why it was measured

It is the outcome these products are sold to change.

Statistical vs. clinical meaning

Where a loss appears it is small. The 2020 review counted 2.5 kg or more as clinically significant.

Safety implication

Small weight changes should be weighed against the rare but serious harms on the Safety tab.

Study	Result	People	Product
⁶	-0.04 kg versus control outside Japan; -0.2 to -3.5 kg in Japanese trials	14 trials, overweight or obese adults	Green tea preparations, 12 to 13 weeks
⁸	No effect for green tea or Garcinia as single agents; combinations not clinically significant	54 trials, overweight or obese adults	Herbal medicines and combinations
⁹	Green tea -1.25 kg (low certainty)	111 trials, 6,171 adults	18 nutraceuticals

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Other 3

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Waist circumference

No clear change outside Japan; mixed in Japanese trials in trials

The distance around the waist in centimetres, a simple sign of belly fat.

Low certainty

Results and what it means

Why it was measured

Fat-burner products are often sold for belly fat.

Statistical vs. clinical meaning

The pooled change outside Japan is within chance.

Safety implication

None specific.

Study	Result	People	Product
⁶	-0.2 cm (CI -1.4 to 0.9) outside Japan; from +1 cm to -3.3 cm in Japanese trials	13 trials, overweight or obese adults	Green tea preparations

⁶

●

Blood pressure and heart rate

Rose with bitter orange (synephrine) in trials

Blood pressure is the force of blood on artery walls (top and bottom numbers, in mmHg). Heart rate is beats per minute.

Low certainty

Results and what it means

Why it was measured

Stimulant ingredients can strain the heart, so trials track these.

Statistical vs. clinical meaning

A rise of this size matters for people with heart disease or high blood pressure.

Safety implication

People with heart conditions should ask a doctor before any stimulant blend.

Study	Result	People	Product
⁷	Systolic +6.37 mmHg, diastolic +4.33 mmHg after prolonged use	18 placebo-controlled trials	Bitter orange or p-synephrine

⁷

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Fat mass and body fat percentage

Small drop overall; no change in high-quality CLA trials in trials

The share of body weight that is fat, measured by body composition scans or similar tools.

Low certainty

Results and what it means

Why it was measured

Fat-burners claim to reduce fat rather than only water or muscle.

Statistical vs. clinical meaning

The best trials show no fat loss.

Safety implication

None specific.

Study	Result	People	Product
¹	Fat mass WMD -0.44 (CI -0.66 to -0.23); body fat -0.77%; no change in high-quality subgroup	70 trials, 4,159 people	CLA supplements

Safety

What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.

Main points to know 4

Hidden prescription drugs are a repeated finding in weight-loss products. The FDA says many diet pills, fat-burning pills, weight-loss supplements and teas are likely to be contaminated with dangerous hidden ingredients, and that they can lead to hospitalization. In FDA warnings from 2007 through 2016, 317 of 776 adulterated supplements were sold for weight loss, and the hidden drug in 85% of those was sibutramine, a banned weight-loss drug. A 2021 lab test of 137 herbal weight-loss products in the United Arab Emirates found undeclared sibutramine in 15.3%, phenolphthalein in 13.9% and fluoxetine in 5.1%. The FDA says its list covers only a small fraction of such products, so a product not on it is not necessarily safe. Regulator warning, analysis of FDA warnings, and laboratory analysis ^{15 14 10 5}
Liver injury, including liver transplant and death, has been linked to weight-loss supplements. A US investigation of 40 acute hepatitis cases found 25 had taken one multi-ingredient weight-loss and sports product; 17 of 22 with data were hospitalized and one had a liver transplant. A US liver-injury network linked 22 cases to Garcinia cambogia (alone or with green tea): one died, one had a transplant and 91% were hospitalized. A 2025 review found more than 200 Garcinia liver-injury events, with one death and nine transplants among 34 case reports. Six cases tied to one family of weight-loss products with green tea extract included one transplant. These are case reports and registries, so they show a real signal but cannot give a rate. Yellow skin or eyes, dark urine or severe tiredness need prompt medical care. Outbreak investigation, registry case series and case report review ^{2 11 19 12}
What is on the label often does not match what is in the bottle. In a lab test of 44 weight-loss supplements bought on or near US military bases, 36 (82%) had inaccurate labels, 16 (36%) had hidden ingredients, and none had a third-party certification seal. In 30 products sold online with military discounts, 25 had inaccurate labels and 7 had hidden components. Many products contained several stimulants, so the combined safety was unknown. These are selected sets of products, not a survey of the whole market. Laboratory case series ^{3 4}
Stimulant ingredients can raise blood pressure and heart rate. A 2022 meta-analysis of placebo-controlled trials found bitter orange (synephrine) raised systolic pressure by 6.37 mmHg and diastolic by 4.33 mmHg after prolonged use, and tends to raise heart rate. Green tea extract side effects listed by NCCIH include increased blood pressure. Caffeine from every source adds up: the FDA has cited 400 mg a day as an amount not generally associated with negative effects for most adults, with wide variation in sensitivity. This is a regulator statement, not advice to use any amount. Meta analysis and regulator statements ^{7 16 13}

Side effects 5

Effect	How often	Severity and recovery	Evidence
Liver injury with jaundice (yellow skin or eyes), dark urine, tiredness Cases were often of multi-ingredient products, so the exact cause is not always clear.	No rate found; 22 high-confidence Garcinia cases in a network of 1,418 liver-injury patients; 6 cases from one product family among 1,091	Can be life-threatening Many recover after stopping; some need transplant; deaths reported	Registry case series and case reports ^{11 19 12 2}
Raised blood pressure and heart rate Heart rate tended to rise too; no figure in the abstract.	Systolic +6.37 mmHg, diastolic +4.33 mmHg with prolonged bitter orange use in pooled trials	Moderate; matters for heart disease and high blood pressure Not studied	Meta-analysis ⁷
Effects of hidden prescription drugs (for example sibutramine, fluoxetine, phenolphthalein) The effects depend on which drug is hidden and on the person's other medicines and health conditions.	Hidden drugs in 17.5% of 137 products in one lab test	Can be serious; the FDA says hospitalization can result Not studied	Laboratory analysis and regulator warning ^{5 15}
Nausea, constipation, abdominal discomfort (green tea extract supplements) NCCIH lists these for green tea extract supplements, not drinking green tea.	No rate given by the source	Mild to moderate Not stated	Authoritative guidance ¹⁶
Allergic reaction Blends contain many ingredients; check the label for known allergens.	Not studied for these blends in the sources read	Not applicable Not applicable	None found

Liver

Liver injury is the most serious documented harm for this product type. A 2013 US investigation (40 cases, 25 with one named multi-ingredient product) found jaundice, fatigue and dark urine, 77% hospitalization among those with data, and one transplant. The US Drug-Induced Liver Injury Network linked 22 cases to Garcinia cambogia (with or without green tea): onset 13 to 223 days after starting, hepatocellular injury, one death, one transplant, 91% hospitalized. A person's gene variant HLA-B*35:01 was more common in these patients (55% versus 19%), suggesting an immune reaction. NCCIH says liver injury from green tea products is uncommon, mainly with extracts in tablets or capsules, and that people with a specific gene variant seem especially susceptible (5 to 15 percent of Americans have it). A 2025 review led the US Pharmacopeia to add a liver caution to its Garcinia monographs. ^{2 11 12 19 16}

How often. No rate of liver injury in users could be found. The studies are case series and reports.

Monitoring. No agency monitoring advice for these products was read. NCCIH advises talking with a health care provider before using green tea supplements.

p27367536.
p34400337.
p27189593.
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This is a safety connection. It is not evidence that Fat Burners and Weight-Loss Blends supports liver health.

Medicines and supplements 6

With	Why it matters	Importance	Evidence	What to do
Green tea extract with atorvastatin, nadolol and raloxifene prescription	NCCIH reports green tea extract can lower blood levels of atorvastatin; high doses of green tea lowered nadolol levels; a funded study showed an interaction with raloxifene.	A lower blood level of a medicine can mean it works less well.	Authoritative guidance Low certainty ¹⁶	Tell a pharmacist about all supplements. Do not stop a prescribed medicine on your own.
Hidden drug ingredients with medicines and health conditions prescription	Hidden drugs such as sibutramine or fluoxetine act like prescription medicines.	The 2018 analysis says hidden ingredients may cause serious effects through misuse, overuse or interaction with other medicines, health conditions or other drugs in the product.	Analysis of FDA warnings Low certainty ¹⁰	A pharmacist cannot check a hidden ingredient. If you take medicines, ask a doctor before using any weight-loss product.
Caffeine and other stimulants (blood pressure and heart medicines, other caffeine products) prescription	Caffeine from drinks and pills adds up; the FDA says some medications can make people more sensitive to caffeine.	Stimulants in blends can raise blood pressure and heart rate (bitter orange meta-analysis).	Regulator statement and meta analysis Low certainty ^{13 7}	Ask a doctor or pharmacist, especially with heart conditions or high blood pressure.
Garcinia combined with green tea supplement	16 of 22 Garcinia liver-injury cases also took green tea.	The authors say the injury from Garcinia and green tea is clinically indistinguishable.	Registry case series Low certainty ¹¹	Check labels for both ingredients; ask a clinician if you have liver problems.
Taking several supplements at once supplement	The same ingredient, or several stimulants, can appear in more than one product.	A 2021 lab study notes people who take several supplements a day may have high combined exposure to harmful compounds; a 2024 study notes multiple stimulants in products made safety unknown.	Laboratory analysis Not enough evidence ^{5 3}	Add up every product's ingredients and ask a pharmacist.
Prescription medicines (general) prescription	No mechanism found for finished blends.	No interaction study of a finished blend with a medicine was found in the sources read.	Absence of evidence Not enough evidence	Absence of a study is not proof of safety. Tell a doctor or pharmacist about every supplement.

Who should check first 5

Situation	Advice	Evidence
Pregnancy, trying to conceive and breastfeeding	The FDA recommends talking to a health care provider about limiting caffeine. NCCIH says caffeine can pass to an infant in breast milk. No safety trials of finished blends in pregnancy or breastfeeding were found. Ask a doctor or midwife before use.	Regulator statements and absence of evidence ^{13 16}
Children and teens	No trials of these blends in children were found. The FDA notes medical experts advise against energy drinks for children and teens. Do not give weight-loss products to a child without a doctor's advice.	Regulator statement and absence of evidence ¹³
*Liver disease, or the HLA-B35:01 gene variant**	Ask a doctor first. NCCIH says people with a specific immune gene variant seem especially susceptible to green tea liver injury; the variant HLA-B*35:01 was more common in Garcinia liver-injury patients.	Authoritative guidance and registry case series ^{16 11}
Heart conditions, high blood pressure, or taking blood pressure medicines	Ask a doctor first. Bitter orange raised blood pressure in pooled trials, and green tea extract side effects include increased blood pressure.	Meta analysis and authoritative guidance ^{7 16}
Anyone taking prescription medicines	Tell a doctor or pharmacist about every product, including weight-loss pills and teas.	Authoritative guidance ^{16 14}

Overdose, product quality and regulators

Summary. No single poisoning dose can be given for a blend, because contents differ by product and may include hidden drugs. Documented serious harm is mainly liver injury and cardiovascular strain.

Animal. Not reviewed.

High dose or long term signals. Liver injury appeared 13 to 223 days after starting Garcinia products. Long-term safety of blends was not found.

Overdose response. Not found.

Genotoxicity. Not researched.

Hidden drugs and inaccurate labels are the main quality problems reported. Metals, microplastics and microbial contamination of these products were not researched here.

Hidden prescription drugs. 317 of 776 FDA-warned adulterated supplements were weight-loss products; sibutramine was the hidden drug in 84.9% of them. In the UAE lab test, 17.5% of 137 products held an undeclared drug. ^{10 5}

Label accuracy. 36 of 44 products from stores near military bases (82%) and 25 of 30 sold online had inaccurate labels; many listed ingredients were not found, and some hidden ingredients were present. ^{3 4}

Marketing wording. The FDA says 'herbal' or 'all natural' does not mean a product is true to its label or safe, that it does not approve facilities, and to beware of products with many rave reviews. ¹⁴

Body	Action	Date
US Food and Drug Administration (Weight Loss Product Notifications) (United States)	Many diet pills, fat-burning pills, weight-loss supplements and teas are likely to be contaminated with dangerous hidden ingredients, are not guaranteed to work, and can lead to hospitalization. The list covers only a small fraction of such products. source	2026-09-04
US Food and Drug Administration (Avoiding Products Contaminated with Hidden Ingredients) (United States)	Hidden ingredients are often prescription drug ingredients, banned substances or harmful chemicals. A weight-loss product could contain sibutramine, a banned drug, yet be sold as 'all-natural'. The FDA does not approve dietary supplements before sale. source	2025-06-10
US Food and Drug Administration (caffeine) (United States)	For most adults the FDA has cited 400 milligrams of caffeine a day as an amount not generally associated with negative effects, with wide variation in sensitivity. Pregnant, trying-to-conceive or breastfeeding people are told to talk to a health care provider about limiting caffeine. This is a regulator statement, not advice. source	2024-08-28
NCCIH (US National Center for Complementary and Integrative Health), Green Tea (United States)	No safety concerns for green tea as a drink in adults. Green tea extract supplements can cause nausea, constipation, abdominal discomfort and increased blood pressure, and uncommonly liver injury, mainly with extracts in tablets or capsules. Green tea extract can lower blood levels of atorvastatin. source	2025-02
United States Pharmacopeia (Garcinia monographs) (United States)	According to a 2025 review, reports of liver injury led USP to revise its Garcinia monographs to include a cautionary statement about potential liver damage. The monographs themselves were not read. source	2025

When to get medical help

Chest pain, a racing or irregular heartbeat, trouble breathing or fainting after taking a fat-burner or weight-loss product: call emergency services (911 in the US).
Yellow skin or eyes, dark urine, severe tiredness or unusual fatigue after starting a weight or sports supplement: stop it and see a doctor promptly.
Swelling of the face, lips or tongue, hives or wheezing after a product: call emergency services.
If you think a product holds a hidden drug, keep the package and tell a doctor or pharmacist; in the US it can be reported to the FDA.

Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.

General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.

Frequently asked questions

What are fat burners?

Fat burners are pills, capsules and teas that mix ingredients such as caffeine and plant extracts and are sold for weight loss. 'Fat burner' is a marketing term, not a medical one.

^{15 18}

Do fat burners work?

No trial of a finished blend was found. Reviews of single ingredients show small average changes, often not large enough to matter. A 2020 review of 54 trials found not enough evidence to recommend any herbal medicine for weight loss.

⁸

Why do the ingredients have trials but the blends do not?

Researchers can test one ingredient against placebo. Each store blend has its own mix, so results for one ingredient cannot be added up to tell what a mix does.

^{8 9}

Does green tea extract help with weight?

A Cochrane review found a small weight change that was unlikely to matter. A 2023 network review found about 1.25 kg on average, with low certainty. Concentrated extracts have also been linked to uncommon liver injury.

^{6 9 16}

Can weight-loss pills contain drugs that are not on the label?

Yes. The FDA says many are likely to be contaminated with hidden ingredients. In FDA warnings from 2007 to 2016, sibutramine, a banned weight-loss drug, was the hidden drug in 85% of the weight-loss products listed.

^{15 10}

Can fat burners hurt the liver?

They can. A US network linked 22 cases of liver injury to Garcinia cambogia, with one death and one transplant, and a 2013 US investigation linked 25 of 40 hepatitis cases to one weight-loss product. Rates of harm are not known.

^{11 2 19}

Do they raise blood pressure?

Bitter orange (synephrine) raised systolic pressure by 6.37 mmHg and diastolic by 4.33 mmHg in pooled trials after prolonged use. Green tea extract supplements can raise blood pressure too, says NCCIH.

^{7 16}

Do labels match what is in the product?

Often not in lab tests. 36 of 44 products from stores near US military bases had inaccurate labels, and 25 of 30 sold online did. These were selected products, not all products.

^{3 4}

Does 'natural' or 'herbal' mean safe?

No. The FDA says these words do not mean a product is true to its label or safe, and that being made in an 'FDA-approved facility' means little because the FDA does not approve facilities.

¹⁴

Are they safe in pregnancy, breastfeeding or for children?

No safety trials of these blends were found. The FDA suggests pregnant, breastfeeding and trying-to-conceive people talk to a provider about limiting caffeine. Ask a doctor first, and do not give them to children without medical advice.

^{13 16}

What signs mean I should stop and get help?

Chest pain, a racing heartbeat, trouble breathing or fainting need emergency help. Yellow skin or eyes, dark urine or severe tiredness need a prompt doctor visit.

^{2 15}

Who should ask a doctor first?

Anyone taking medicines, and people who are pregnant or breastfeeding or who have liver disease, heart disease or high blood pressure. Green tea extract can lower blood levels of some medicines, such as atorvastatin.

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Explore by health goal

Weight Management

Editorial transparency

Written by: AlternativeMed editorial team. Research compiled with AI assistance, then checked against the sources listed.
Medical review: None. This page has not been reviewed by a physician or pharmacist.
First published: 2026-10-26
Last substantive update: 2026-10-26
How we research: We started from our existing page on this product type, then re-read PubMed abstracts for every review, trial, case series and lab study cited, and opened the FDA and NCCIH pages. Only abstracts were read, not full texts. The NIH Office of Dietary Supplements page was blocked and is marked unverified.
How we rate evidence: See "How we rate evidence" in the Evidence tab.
Independence: No product is promoted on this page. No affiliate links are shown. No brand names are used. Funding and conflict statements are shown where the abstracts give them.

Sources 19

Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.

Asbaghi O, Shimi G, Hosseini Oskouie F, et al.. The effects of conjugated linoleic acid supplementation on anthropometrics and body composition indices in adults: a systematic review and dose-response meta-analysis.. Br J Nutr. 2024. PMID 37671495. DOI 10.1017/S0007114523001861. (abstract)
Chatham-Stephens K, Taylor E, Chang A, et al.. Hepatotoxicity associated with weight loss or sports dietary supplements, including OxyELITE Pro - United States, 2013.. Drug Test Anal. 2017. PMID 27367536. DOI 10.1002/dta.2036. (abstract)
Crawford C, Lindsey AT, Avula B, et al.. Label Accuracy and Quality of Select Weight-Loss Dietary Supplements Sold on or near US Military Bases.. Nutrients. 2024. PMID 39770990. DOI 10.3390/nu16244369. (abstract)
Crawford C, Avula B, Lindsey AT, et al.. Label Accuracy of Weight Loss Dietary Supplements Marketed Online With Military Discounts.. JAMA Netw Open. 2024. PMID 38691359. DOI 10.1001/jamanetworkopen.2024.9131. (abstract)
Jairoun AA, Al-Hemyari SS, Shahwan M, et al.. Adulteration of Weight Loss Supplements by the Illegal Addition of Synthetic Pharmaceuticals.. Molecules. 2021. PMID 34833995. DOI 10.3390/molecules26226903. (abstract)
Jurgens TM, Whelan AM, Killian L, et al.. Green tea for weight loss and weight maintenance in overweight or obese adults.. Cochrane Database Syst Rev. 2012. PMID 23235664. DOI 10.1002/14651858.CD008650.pub2. (abstract)
Koncz D, Toth B, Bahar MA, et al.. The Safety and Efficacy of Citrus aurantium (Bitter Orange) Extracts and p-Synephrine: A Systematic Review and Meta-Analysis.. Nutrients. 2022. PMID 36235672. DOI 10.3390/nu14194019. (abstract)
Maunder A, Bessell E, Lauche R, et al.. Effectiveness of herbal medicines for weight loss: A systematic review and meta-analysis of randomized controlled trials.. Diabetes Obes Metab. 2020. PMID 31984610. DOI 10.1111/dom.13973. (abstract)
Shahinfar H, Jayedi A, Torabynasab K, et al.. Comparative effects of nutraceuticals on body weight in adults with overweight or obesity: A systematic review and network meta-analysis of 111 randomized clinical trials.. Pharmacol Res. 2023. PMID 37778464. DOI 10.1016/j.phrs.2023.106944. (abstract)
Tucker J, Fischer T, Upjohn L, et al.. Unapproved Pharmaceutical Ingredients Included in Dietary Supplements Associated With US Food and Drug Administration Warnings.. JAMA Netw Open. 2018. PMID 30646238. DOI 10.1001/jamanetworkopen.2018.3337. (abstract)
Vuppalanchi R, Bonkovsky HL, Ahmad J, et al.. Garcinia cambogia, Either Alone or in Combination With Green Tea, Causes Moderate to Severe Liver Injury.. Clin Gastroenterol Hepatol. 2022. PMID 34400337. DOI 10.1016/j.cgh.2021.08.015. (abstract)
Zheng EX, Rossi S, Fontana RJ, et al.. Risk of Liver Injury Associated with Green Tea Extract in SLIMQUICK Weight Loss Products: Results from the DILIN Prospective Study.. Drug Saf. 2016. PMID 27189593. DOI 10.1007/s40264-016-0428-7. (abstract)
. US FDA: Spilling the Beans: How Much Caffeine Is Too Much?. . . (page)
. US FDA: Avoiding Products Contaminated with Hidden Ingredients. . . (page)
. US FDA: Weight Loss Product Notifications (Medication Health Fraud). . . (page)
. NCCIH (US): Green Tea. . . (page)
. NIH Office of Dietary Supplements: weight-loss fact sheet. . . (not-read)
. Existing AlternativeMed page for this formula type (read 2026-10-26). . . (summary-only)
van Breemen RB, Roe AL, Akhtar N. Hepatotoxicity of dietary supplements containing Garcinia gummi-gutta (L.) N. Robson.. Pharm Biol. 2025. PMID 41262061. DOI 10.1080/13880209.2025.2591467. (abstract)

Where to buy

Check the label first. Whatever you buy, look for these:

The amount of the active ingredient per serving, not just the front-label claim
A third-party testing mark (USP, NSF or ConsumerLab)
Other ingredients and allergens
Ask a pharmacist about interactions with your medicines

Talk to a pharmacist or doctor before you start any supplement, especially if you take medicines. See the Safety tab for interactions.

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Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.