Intermittent fasting for women over 40

Does fasting still work after menopause?

Alternate-day fasting is a different pattern from the daily windows in Fasting Tracker, and these were small trials. But they're a reassuring sign that menopause doesn't switch fasting off.

What about your hormones?

You'll find claims online that fasting wrecks women's hormones. A review of human trials found that fasting had no effect on estrogen, the brain hormones that control ovulation, or prolactin in women, though it lowered androgens such as testosterone in premenopausal women with obesity. Very few studies exist, so firm conclusions aren't possible yet ². In perimenopause, cycles often change on their own; see fasting and your period.

Protect your muscle

Muscle matters more with every decade. In a 12-week trial, people on 16:8 without any exercise lost more lean mass from their arms and legs than people eating three meals a day ³. With strength training and enough protein, young trained women on a short window gained as much lean mass and strength as those eating across the day ⁴.

Aim for protein at every meal. Gains from strength training level off at about 1.6 g per kilo of body weight a day ⁵. For adults over 65, experts recommend at least 1.0 to 1.2 g per kilo, and more if you're active ⁶. The protein calculator works out your target.

Look after your bones

Strength training helps bone as well as muscle. In the LIFTMOR trial, 101 postmenopausal women with low bone mass did 30 minutes of supervised, high-intensity strength and impact training twice a week for 8 months. Bone density in the spine and hip improved compared with a gentle home programme, with only one minor injury ⁷. The training was closely supervised, so start with a qualified coach. And don't let a short window crowd out calcium-rich foods such as dairy, fortified plant milks, tofu and leafy greens.

Hot flushes and sleep

If hot flushes or night sweats wake you, fasting can feel harder the next day: after two short nights, healthy young men had 28% more ghrelin, the hunger hormone, and felt 24% hungrier ⁸. We haven't found good evidence that fasting eases hot flushes, or that it makes them worse.

• After a broken night, it's fine to shorten your fast.
• Finish eating a few hours before bed, and have your last coffee at least 6 hours before it ⁹.
• Notice whether alcohol, spicy food or hot drinks late in the evening seem to set off your flushes.

A gentle way to fast

When to talk to a doctor

• Before you start, if you take regular medication or have a condition such as diabetes, high blood pressure or osteoporosis.
• If you have any bleeding after menopause, or bleeding that's much heavier or more frequent than usual: get it checked, whether or not you fast.
• If you feel dizzy, faint or unusually tired, or lose weight without trying.

Sources

1. Lin S, Lima Oliveira M, Gabel K, et al. Does the weight loss efficacy of alternate day fasting differ according to sex and menopausal status? Nutr Metab Cardiovasc Dis. 2021;31(2):641-649. doi.org/10.1016/j.numecd.2020.10.018
2. Cienfuegos S, Corapi S, Gabel K, et al. Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials. Nutrients. 2022;14(11):2343. doi.org/10.3390/nu14112343
3. Lowe DA, Wu N, Rohdin-Bibby L, et al. Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial. JAMA Intern Med. 2020;180(11):1491-1499. doi.org/10.1001/jamainternmed.2020.4153
4. Tinsley GM, Moore ML, Graybeal AJ, et al. Time-restricted feeding plus resistance training in active females: a randomized trial. Am J Clin Nutr. 2019;110(3):628-640. doi.org/10.1093/ajcn/nqz126
5. Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376-384. doi.org/10.1136/bjsports-2017-097608
6. Bauer J, Biolo G, Cederholm T, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013;14(8):542-59. doi.org/10.1016/j.jamda.2013.05.021
7. Watson SL, Weeks BK, Weis LJ, et al. High-Intensity Resistance and Impact Training Improves Bone Mineral Density and Physical Function in Postmenopausal Women With Osteopenia and Osteoporosis: The LIFTMOR Randomized Controlled Trial. J Bone Miner Res. 2018;33(2):211-220. doi.org/10.1002/jbmr.3284
8. Spiegel K, Tasali E, Penev P, et al. Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med. 2004;141(11):846-50. doi.org/10.7326/0003-4819-141-11-200412070-00008
9. Drake C, Roehrs T, Shambroom J, et al. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med. 2013;9(11):1195-200. doi.org/10.5664/jcsm.3170
10. Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. doi.org/10.3390/nu11040873