Why Weight Changes: Gain, Plateaus and Midlife
Why weight can creep up, stall or shift in midlife: habits, sleep, medicines, health conditions, how the body adapts to weight loss, and when to talk to a clinician.
Content last updated . This page has not been medically reviewed.
Overview
Weight changes for many reasons, and the cause is often a mix. This page covers gaining weight, weight loss plateaus (when the scale stops moving) and midlife changes. It explains common contributors; it cannot tell you the cause in your own case. If your weight is going down without trying, see Unintentional weight loss instead.Common reasons weight goes up
| Contributor | What the source says | Source type |
|---|---|---|
| Energy balance | If you take in more calories from food and drink than you use, your body may store some of the extra as fat. [1] | NIDDK health information |
| Sleep | Not getting enough sleep is linked to weight gain and may make you feel hungrier and more likely to choose less healthy foods. [1] | NIDDK health information |
| Medicines | Some medicines for epilepsy, depression or psychotic disorders, steroids, some diabetes medicines, some blood pressure medicines and some antihistamines may contribute. [1] See Medicines that can change weight. | NIDDK health information |
| Health conditions | Examples include polycystic ovary syndrome, Cushing's syndrome, an underactive thyroid, depression and long-term stress. [1] | NIDDK health information |
| Eating disorders | Binge eating disorder and bulimia may lead to weight gain or obesity. [1] | NIDDK health information |
| Genes and family history | Your chances of overweight or obesity are greater if one or both parents have it. [1] | NIDDK health information |
| Life stage | NHS lists being over 55 and being menopausal or perimenopausal among things that can make staying at a healthy weight harder. [2] | NHS |
Why plateaus happen
A plateau is common, and it does not mean you failed. A mathematical model of adult metabolism found that body weight responds slowly to a change in energy intake, with half times of about 1 year. [3] The same model builds in energy-use changes during weight loss, because the body adapts. [3] A review describes what can happen after weight loss: hunger rises, hormones that signal fullness fall, and the body can use less energy than expected for its new size. [4]Proper evidence not found: the sources I could read did not include trial-based methods for "breaking" a plateau, so this page does not offer tips for that. Talking with a registered dietitian or your clinician about your own pattern is a reasonable next step. For more on metabolism, see Metabolism: what it is and whether you can boost it.
Midlife and menopause
NHS says weight gain during perimenopause and menopause is common and often happens around the stomach and upper body. [5] A review of the research concluded that weight gain itself cannot be attributed to the menopause transition, but the hormone changes are associated with more total body fat and more abdominal fat. [6]Age alone may not explain it. In a large study using doubly labeled water (a precise way to measure energy use), energy use adjusted for body size stayed stable from age 20 to 60 and then declined in older adults. [7] The same review of menopause research notes that estrogen therapy may partly prevent the shift in body composition but that more studies are needed to identify who benefits. [6] Hormone therapy is a medical decision, not a weight-loss method; see Perimenopause and menopause.
What may help (overview)
Evidence-based habits for weight overall are covered in Healthy weight basics, Sleep, stress and the food environment and Activity, strength and keeping muscle. A sleep-extension trial in adults with overweight who slept under 6.5 hours found lower calorie intake with more sleep (a small, single trial: promising but limited). [8]When to get help
NHS advises speaking to a GP if a health condition makes it harder to stay at a healthy weight. [2] Ask about weight changes at a visit where your clinician can also review your medicines, since NIDDK says a clinician may review the medicines and supplements you take to see whether they affect weight. [9]Frequently asked questions
Why did I gain weight without changing what I eat?
Several things can contribute, including sleep, medicines, health conditions, stress and life stage. [1] A clinician can help sort out which may apply to you.
Does metabolism slow down after 40?
In one large study of energy use measured with doubly labeled water, size-adjusted energy use did not decline from age 20 to 60. [7] That does not mean midlife changes are imaginary; body composition and activity can shift. [6]
Is menopause weight gain unavoidable?
The research reviewed here does not say it is unavoidable. It links the menopause transition to more abdominal fat, while noting that weight gain itself cannot be attributed to menopause alone. [6]
References
- NIDDK. Factors affecting weight and health. Read 2026-10-22 (page last reviewed May 2023).
- NHS. Overweight and obesity in adults. Read 2026-10-22.
- Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011. Read 2026-10-22.
- Melby CL et al. Attenuating the biologic drive for weight regain following weight loss: must what goes down always go back up? Nutrients 2017. Read 2026-10-22.
- NHS. Menopause: symptoms. Read 2026-10-22.
- Davis SR et al. Understanding weight gain at menopause. Climacteric 2012. Read 2026-10-22.
- Pontzer H et al. Daily energy expenditure through the human life course. Science 2021. Read 2026-10-22.
- Tasali E et al. Effect of sleep extension on objectively assessed energy intake among adults with overweight in real-life settings. JAMA Intern Med 2022. Read 2026-10-22.
- NIDDK. Choosing a safe and successful weight-loss program. Read 2026-10-22.