Key takeaways
- The age term in the equation takes off only about 5 kcal of resting burn a year.
- Around menopause the rate of fat gain roughly doubles and lean mass begins to fall, then both level off about two years after the final period.
- Muscle and daily movement are the parts of TDEE you can protect, and they matter more than age itself.
- There is little evidence that HRT causes weight gain; decide on it with your doctor for your symptoms.
On this page
- Your metabolism doesn’t fall off a cliff at 40
- What actually changes after 40
- How much does TDEE really drop?
- What happens around menopause
- Five habits that protect your TDEE
- Example: a 48-year-old woman losing 6 kg
- Losing weight after 40
- HRT and your weight
- Bones: the other reason to lift
- Questions about TDEE for women over 40
Your metabolism doesn’t fall off a cliff at 40
It is one of the most repeated ideas in nutrition: turn 40 and your metabolism slows down. The best evidence says otherwise. A 2021 study published in Science pooled measurements of daily energy use from more than 6,000 people in 29 countries, from babies to people in their nineties, using the doubly labelled water method, the most accurate way to measure energy use in daily life. Once differences in body size and composition were accounted for, energy use was remarkably stable from about age 20 to 60. It only started to fall after 60, by about 0.7% a year.
So if you are eating the same as you did at 35 and slowly gaining weight at 45, the cause is rarely a broken metabolism. It is usually a combination of smaller changes, most of which you can do something about.
What actually changes after 40
- Muscle. Without strength training, muscle mass tends to fall gradually through midlife and faster after 60. Less muscle means a slightly lower resting burn and, more importantly, less strength for everyday movement.
- Everyday movement. Busier jobs, caring for children or parents, joint pain and tiredness all reduce the walking, standing and fidgeting that make up a large part of TDEE. This is usually the biggest change, and the easiest to miss.
- Sleep. Night sweats, waking early and stress make sleep worse for many women in their 40s and 50s. Tired people tend to move less and eat more.
- Menopause. Falling oestrogen shifts where fat is stored and how much lean mass you keep, as described below.
- Medicines. Some medicines that become more common with age can affect appetite or weight. Ask your doctor if you have noticed a change after starting one.
How much does TDEE really drop?
Take a woman who is 163 cm (5′4″) and 68 kg (150 lb), lightly active at 40. At 55, the equation alone gives her a TDEE about 103 kcal lower, from 1,839 to 1,736 kcal, simply because she is 15 years older. Real life usually adds a little more:
| Change between 40 and 55 | Typical effect on TDEE |
|---|---|
| 15 years older (equation only) | About −100 kcal |
| 2 kg (4.4 lb) less muscle | About −25 to −35 kcal |
| 2,000 fewer steps a day | About −40 to −60 kcal |
| Total | About −165 to −195 kcal a day |
That is roughly a slice of buttered toast a day: small on any one day, but it adds up over months. Eating exactly what she ate at 40 could explain a slow gain of a few kilos over the years. The good news is that two of the three rows are within her control.
What happens around menopause
The Study of Women’s Health Across the Nation (SWAN), which followed women through the menopause transition, found that fat mass was already rising slowly before the transition. Once the transition began, the rate of fat gain roughly doubled and lean mass started to fall. Both trends continued until about two years after the final period, then levelled off. Interestingly, body weight itself rose steadily through the premenopausal years without a sudden jump at the transition; what changed most was body composition.
A smaller study that measured energy use in a whole-room calorimeter over four years found that women who became postmenopausal gained visceral (deep abdominal) fat, while those who stayed premenopausal did not. Their energy use during sleep fell more, and the amount of fat they burned for fuel dropped by about a third. Their physical activity had also fallen, starting about two years before menopause.
The practical message: around menopause, protecting muscle and daily movement matters even more than before, and fat is more likely to settle around the middle.
Five habits that protect your TDEE
- Lift weights two or three times a week. Full-body sessions with gradually heavier weights hold on to muscle, protect your bones and keep everyday tasks easy. It is never too late to start; women in their 60s and 70s gain strength quickly with training.
- Eat enough protein. The 2025 to 2030 US Dietary Guidelines note that older and physically active adults may benefit from about 1.2 to 1.6 g per kg of body weight a day. If you are losing weight and lifting, aim for the higher end or a little more, spread over three or four meals of 25 to 40 g. The protein calculator gives you a range.
- Keep your steps up. Set a daily step target and protect it, especially if your job is sedentary. Walking is gentle on joints and good for mood and sleep too. The steps calculator shows what your steps add to your TDEE.
- Protect your sleep. If night sweats or insomnia are keeping you up, talk to your doctor. Treatments, including hormone therapy and cognitive behavioural therapy for insomnia, can help.
- Measure instead of guessing. Rather than cutting food “because of age”, measure what you really burn. Log your food and weigh yourself for three to four weeks, then use the adaptive TDEE calculator.
Example: a 48-year-old woman losing 6 kg
A 48-year-old woman, 165 cm (5′5″) and 76 kg (168 lb), works at a desk and walks most days, so she is lightly active. She wants to lose about 6 kg (13 lb).
BMR = 10 × 76 + 6.25 × 165 − 5 × 48 − 161 = 1,390 kcal TDEE = 1,390 × 1.375 = 1,912 kcal Target (15% below TDEE): about 1,625 kcal a day Expected loss: about 0.25 kg (½ lb) a week Protein: about 91 to 122 g a day (1.2 to 1.6 g/kg)
A 15% deficit is gentle enough to keep up for months while she lifts twice a week. If her periods are irregular, the scale will bounce with water at unpredictable times, so she judges progress from four-week trends and her waist measurement rather than any single week.
Losing weight after 40
The method doesn’t change after 40, but a few details matter more:
- Choose a moderate deficit, 15 to 20% below TDEE, and stay above about 1,200 kcal a day. Very low intakes cost muscle, which you are already working to keep.
- Expect water swings. Irregular cycles in perimenopause make the scale less predictable. Look at four-week trends.
- Be patient with the middle. Fat around the waist often goes last. Measuring your waist every two weeks shows progress the scale can hide.
- Recalculate every 4 to 5 kg (10 lb) and whenever your routine changes.
HRT and your weight
Many women worry that hormone replacement therapy will make them gain weight. The NHS says there is little evidence that most types of HRT do, and that the weight many women gain around menopause and with age often happens whether they take HRT or not. HRT is a treatment for menopausal symptoms, not a weight-loss tool, and the decision to take it should be based on your symptoms, your health history and a conversation with your doctor. If you start it, keep your calorie target the same and judge any change from your four-week trend.
Bones: the other reason to lift
Bone loss speeds up in the years around menopause as oestrogen falls. Strength training and impact activities such as brisk walking, stair climbing or skipping help maintain bone density, along with enough protein, calcium and vitamin D. This matters far more for your long-term health than a few calories of TDEE, and it is one more reason to make lifting a regular habit.
Questions about TDEE for women over 40
Is it harder to lose weight after 40?
A little, mostly because muscle, daily movement and sleep tend to fall, not because metabolism suddenly slows. The same approach works: a moderate deficit, strength training, enough protein and patience.
Should I eat less just because I’m older?
Not automatically. Your equation-based TDEE falls by only about 5 kcal of resting burn a year. Recalculate with your current weight and activity, or measure your real TDEE from a few weeks of data.
Does HRT change my TDEE or make me gain weight?
There is little evidence that most types of HRT cause weight gain. Weight gain around menopause often happens with or without it. Discuss HRT with your doctor based on your symptoms.
Does menopause slow your metabolism?
Menopause shifts body composition towards more fat and less lean mass, which lowers TDEE slightly. Strength training and protein limit the muscle loss.
How much protein do women over 40 need?
About 1.2 to 1.6 g per kg of body weight a day is a sensible range for active women in midlife, and up to about 1.6 to 2.2 g/kg while dieting and lifting weights.
Is cardio or strength training better after 40?
Both help, but strength training does something cardio can’t: it keeps muscle and bone. Combine two or three strength sessions a week with daily walking or other cardio you enjoy.
Why am I gaining weight around my middle?
Around menopause, falling oestrogen makes fat more likely to be stored around the abdomen, even without much change in weight. A moderate deficit, strength training and enough sleep all help.
Sources
- Pontzer H, Yamada Y, Sagayama H, et al. Daily energy expenditure through the human life course. Science. 2021;373(6556):808-812. doi.org/10.1126/science.abe5017
- Greendale GA, Sternfeld B, Huang M, et al. Changes in body composition and weight during the menopause transition. JCI Insight. 2019;4(5):e124865. doi.org/10.1172/jci.insight.124865
- Lovejoy JC, Champagne CM, de Jonge L, Xie H, Smith SR. Increased visceral fat and decreased energy expenditure during the menopausal transition. Int J Obes (Lond). 2008;32(6):949-958. doi.org/10.1038/ijo.2008.25
- NHS. Side effects of hormone replacement therapy (HRT). www.nhs.uk/conditions/hormone-replacement-therapy-hrt/side-effects/
- Oklahoma State University Extension. The new Dietary Guidelines for Americans 2025 to 2030. Fact sheet. extension.okstate.edu/fact-sheets/the-new-dietary-guidelines-for-americans-2025-2030
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. doi.org/10.1093/ajcn/51.2.241