You're eating much the same way you always have, perhaps exercising regularly, yet your waistline is getting larger or your clothes fit differently. Or maybe your weight hasn't changed much, but your body looks different.
If you're over 40, you may be wondering whether perimenopause is responsible. Are hormonal changes making you gain fat? Is your metabolism slowing down? And why might losing weight feel harder than before?
The research tells a more complicated story than simply blaming hormones or a slower metabolism.
Why Does Body Composition Change During Perimenopause?
Perimenopause commonly begins in the 40s and is characterised by fluctuating reproductive hormones, particularly oestrogen, and changes in menstrual patterns. These hormonal changes can influence fat distribution, appetite regulation and menopausal symptoms.
More Fat, Less Lean Mass
One important finding is that body composition can change even when body weight does not increase dramatically.
A 2019 analysis from the Study of Women's Health Across the Nation (SWAN) found that:
The average annual rate of fat-mass gain increased from approximately 1% to 1.7% during the menopause transition.
Lean mass shifted from a small annual increase to a decrease.
Overall weight continued to increase, but the rate of weight gain did not significantly accelerate at the beginning of the transition. [1]
These were average findings, with differences between population groups. They do not describe what every woman will experience.
Lean mass includes muscle and other non-fat tissues, so a decline in lean mass does not necessarily represent an equivalent loss of skeletal muscle.
Why Does Belly Fat Increase?
Oestrogen is involved in regulating fat distribution. During the menopause transition, women may experience increased accumulation of abdominal fat, including visceral fat stored around internal organs.
In the SWAN Heart Study involving 362 women, visceral fat increased more rapidly during the two years preceding the final menstrual period. Greater accumulation during this period was associated with increased thickness of the inner layers of the internal carotid artery, a marker of subclinical atherosclerosis. [2]
Excess visceral fat is associated with cardiometabolic risk. However, abdominal fat distribution is also influenced by age, genetics, overall body fat and lifestyle.
Does Metabolism Really Slow Down After 40?
A large study involving 6,421 people found that daily energy expenditure, adjusted for body size and composition, remained relatively stable between approximately 20 and 60 years of age. [3]
However, this study did not isolate the effects of menopause.
Oestrogen itself can influence energy expenditure. In a small experimental study, suppressing ovarian hormones in premenopausal women reduced resting energy expenditure by approximately 54 kcal per day. This reduction was not observed in women receiving replacement estradiol. [4]
These findings demonstrate that estradiol can influence resting metabolism, but they do not establish the size of this effect during natural perimenopause.
Furthermore, a five-year MONET study found that declining total energy expenditure among women who reached postmenopause was largely associated with reduced physical activity, while their average resting energy expenditure remained stable. [5]
So although hormonal changes may affect energy regulation, the evidence does not support an inevitable, dramatic metabolic slowdown after 40.
Read more: Does Metabolism Slow Down After 40?
Can Perimenopause Affect Hunger and Fullness?
Oestrogen also participates in appetite regulation, interacting with signalling pathways involving ghrelin, a hormone that stimulates hunger, and leptin, which communicates information about energy stores to the brain.
However, the precise influence of changing oestrogen levels on these systems during natural perimenopause is not fully established.
In a five-year observational MONET study involving 94 women at baseline, researchers reported increased hunger and desire to eat, alongside reduced feelings of fullness before meals. Interestingly, energy intake decreased rather than increased. Individual analyses included smaller groups of participants. [6]
This suggests that women may experience changes in hunger and fullness during the menopause transition without necessarily eating more.
The study does not establish that changes in oestrogen, ghrelin or leptin directly caused these effects.
Why Can Weight Management Feel Harder During Perimenopause?
Changes in body composition and appetite are only part of the picture. Menopausal symptoms may also make it more difficult to maintain eating and exercise routines.
Sleep Disturbances and Fatigue
Sleep problems are common during the menopause transition. Longitudinal research from SWAN found that difficulties falling asleep and staying asleep became more common as women progressed through the transition. Hot flushes and night sweats were important contributing factors, although sleep problems also occurred without them. [7]
Poor sleep may also influence eating behaviour.
In a randomised trial involving adults with overweight who habitually slept less than 6.5 hours per night, an intervention to extend sleep duration reduced average daily energy intake by approximately 270 kcal compared with the control group. [8]
However, this study involved younger adults, not women specifically experiencing perimenopause. Its findings cannot be directly applied to menopause-related sleep disturbances.
Beyond possible effects on appetite, persistent fatigue may make exercising, preparing meals and maintaining routines more demanding.
Stress, Mood and Emotional Eating
Stress can influence food choices and eating behaviour, although responses vary between individuals.
A systematic review and meta-analysis of 54 studies involving 119,820 adults found small associations between stress and increased overall food intake, greater consumption of less healthy foods and reduced consumption of healthier foods. [9]
These findings were not specific to perimenopause and do not establish that hormonal changes cause emotional eating.
Nevertheless, when stress, mood changes, disrupted sleep and fatigue occur together, they may create additional practical barriers to maintaining healthy habits.
This is an important distinction: knowing how to manage your weight and being able to follow a plan consistently are not always the same thing.
Is Perimenopause the Only Explanation for Weight Gain?
No. Changes in body weight during midlife can also reflect ageing, dietary intake, physical activity, medication use and underlying health conditions.
For example, thyroid disorders can contribute to fatigue and weight changes.
Rapid or unexplained weight changes and persistent symptoms deserve medical assessment rather than automatic attribution to perimenopause.
The Bottom Line
Perimenopause is associated with changes in body composition and abdominal fat distribution, even when overall weight changes relatively little. Hormonal changes may also influence energy regulation and appetite, although their precise contribution to weight gain varies and is not fully understood.
At the same time, poor sleep, fatigue and stress may make maintaining healthy eating and activity habits more difficult.
This helps explain why weight management in midlife can become more challenging without implying that weight gain is inevitable or that losing fat becomes impossible.
Understanding what changes is the first step. The next is choosing an approach that addresses both body composition and the everyday factors affecting weight management.
In Part 2, we'll explore what research supports for losing excess body fat while preserving muscle and strength, including nutrition, exercise, managing menopausal symptoms and evaluating weight-loss supplements.
Scientific References
Greendale GA, et al. (2019). Changes in body composition and weight during the menopause transition. JCI Insight, 4(5), e124865.
https://insight.jci.org/articles/view/124865Samargandy S, et al. (2021). Abdominal visceral adipose tissue over the menopause transition and carotid atherosclerosis: The SWAN Heart Study. Menopause, 28(6), 626–633.
https://pubmed.ncbi.nlm.nih.gov/33651741/Pontzer H, et al. (2021). Daily energy expenditure through the human life course. Science, 373, 808–812.
https://pubmed.ncbi.nlm.nih.gov/34385400/Melanson EL, et al. (2015). Regulation of energy expenditure by estradiol in premenopausal women. Journal of Applied Physiology.
https://pubmed.ncbi.nlm.nih.gov/26338457/Duval K, et al. (2013). Effects of the menopausal transition on energy expenditure: A MONET Group Study. European Journal of Clinical Nutrition, 67, 407–411.
https://pubmed.ncbi.nlm.nih.gov/23422924/Duval K, et al. (2014). Effects of the menopausal transition on dietary intake and appetite: A MONET Group Study. European Journal of Clinical Nutrition, 68, 271–276.
https://pubmed.ncbi.nlm.nih.gov/24065065/Kravitz HM, et al. (2008). Sleep disturbance during the menopausal transition in a multi-ethnic community sample of women. Sleep, 31(7), 979–990.
https://pubmed.ncbi.nlm.nih.gov/18652093/Tasali E, et al. (2022). Effect of sleep extension on objectively assessed energy intake among adults with overweight in real-life settings: A randomized clinical trial. JAMA Internal Medicine, 182(4), 365–374.
https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2788694Hill D, et al. (2022). Stress and eating behaviours in healthy adults: A systematic review and meta-analysis. Health Psychology Review, 16(2), 280–304.
https://pubmed.ncbi.nlm.nih.gov/33913377/
This article is intended for general education and does not replace individual medical assessment.
