Weight and Metabolism Safety: Rapid Change, Restrictive Diets, Stimulants and Laxatives

Urgent help first

• Eating disorder crisis or thoughts of suicide (US): call or text 988 (Suicide & Crisis Lifeline), or chat at 988lifeline.org. In a life-threatening emergency, call 911. [1] Elsewhere, use your local emergency number.
• Poisoning or overdose of a supplement, laxative or weight-loss product (US): Poison Help 1-800-222-1222; see Poisoning: what to do first and Poison Help by country.
• UK eating disorder support: Beat's England helpline is 0808 801 0677 (3pm to 8pm Monday to Friday when read); Beat says that if you or someone else is in immediate danger you should contact 999 or the Samaritans on 116 123. [2]
• Serious side effects of a prescribed weight-loss medicine: NHS lists severe stomach or back pain that does not go away, sudden loss of vision, and signs of a severe allergic reaction such as a swollen throat or tongue or difficulty breathing as serious side effects of semaglutide, and advises calling NHS 111 in the UK if you think you are having serious side effects. [3] In the US, contact your prescriber, and call 911 for difficulty breathing or a swollen throat.

Overview

Most people can work on weight habits safely, but some situations carry real risk. This page covers rapid or unexplained change, restrictive diets, stimulants, laxatives, contaminated products, pregnancy and adolescents. It is general information and not a substitute for your clinician. Related pages: Healthy weight basics, Eating disorders and disordered eating and Unintentional weight loss.

Rapid or unexplained change

• Weight loss you did not intend is a reason to see a clinician. NHS says it can be a sign of stress or a serious illness; MedlinePlus defines it as losing 10 pounds (4.5 kg) or 5% of normal body weight over 6 to 12 months or less without knowing why. [4][5]
• Quick-loss promises. NIDDK lists "Lose 30 pounds in 30 days!" and "Lose weight without diet or exercise!" as warning signs of a weight-loss program. [6]
• Unexplained gain can have medical causes, including medicines and conditions such as an underactive thyroid; see Why weight changes. [7]

Restrictive and very low calorie diets

NHS says very low calorie diets are not suitable or safe for everyone and are usually only recommended, with dietitian support, if weight is affecting other health conditions and quick loss is needed. [8] In an AAP report on adolescents, some teenagers trying to lose weight may develop an eating disorder. [9] If diet rules feel rigid, frightening or compulsive, talk to a professional. If you take diabetes or blood pressure medicines, do not change them on your own: in the DiRECT trial they were withdrawn as part of a clinician-led, low-calorie program run in primary care. [10]

Stimulants and "fat burners"

Evidence that stimulant-containing herbal combinations produce clinically significant weight loss is weak, and the FDA warns that many weight-loss products are likely to contain hidden drug ingredients. [11][12] NCCIH lists higher blood pressure among side effects of green tea extract and notes that caffeine intake in pregnancy should not exceed moderate levels. [13] See Weight-loss supplements, fat burners, detox teas and vinegar.

Laxatives and purging

Proper evidence not found that laxatives are an effective or safe way to control weight; the sources describe harms. NHS says using laxatives too often or for too long can cause problems such as dehydration, and over-the-counter laxatives should not be taken for longer than 7 days. [14] MedlinePlus lists overuse of laxatives among causes of unintentional weight loss. [5] NHS lists making yourself sick or taking laxatives after eating as a possible symptom of an eating disorder. [15] A review of bulimia nervosa says purging, including laxative and diuretic misuse, can cause medical complications, especially affecting the kidneys and electrolytes. [16] If you are using laxatives, vomiting or diuretics to control weight, please speak to a clinician; see Eating disorders and disordered eating and Constipation.

Contaminated or adulterated products

The FDA says contaminated weight-loss products are often falsely advertised as dietary supplements, food or all-natural treatments, and may have many positive reviews or be shared on social media. [12] It also warns about unapproved and fraudulent versions of GLP-1 medicines. [17] Buy prescription medicines only from a pharmacy approved by your clinician. [18] See Unsafe products and warnings, Product quality and contamination and Side effects, allergic reactions and reporting.

Pregnancy and breastfeeding

NHS says pregnancy is not the time to go on a diet because it may harm the unborn child, and that too little weight gain can also cause problems. [19] NIDDK says weight-loss medicines should not be taken during pregnancy or when planning pregnancy and are not recommended while breastfeeding. [18] See Pregnancy and breastfeeding and Preconception, pregnancy, postpartum and breastfeeding.

Children and teens

The AAP report says the focus for adolescents should be a healthy lifestyle rather than weight. [9] NIDDK says four prescription weight-management medicines are FDA-approved for children aged 12 and older, and decisions belong with a pediatric specialist. [18] Avoid supplements and diet plans for children or teens without medical advice; see Children and teens.

Medicines, diabetes and other conditions

Tell your prescriber about every medicine and supplement you take. NIDDK says weight-loss medicines may have harmful interactions with other medicines, including herbal products. [18] See Interactions by drug class.

When to get help

See a clinician about weight if you have unexplained change, a health condition, or concerns about eating. NHS suggests seeing a GP if you think you may have an eating disorder, and says a GP can refer you to a specialist. [8][15]