Biohacking Kompakt

Podcast episode 102 (in German)

Intermittent fasting after menopause – the study with an average age of 32

October 10, 2026

The best long-term study on intermittent fasting ran for one year and included 139 people — average age 32. This episode consistently asks who was actually measured before the recommendation reached women past menopause.

What it is about

Intermittent fasting is considered well studied, and for people in general that is true. The episode counts how much of it remains for women in or after perimenopause. The result of this count: in the best review of 28 studies that compare intermittent fasting directly with calorie reduction, not a single one can be assigned to this group beyond doubt. Before that comes the finding one should know first anyway — compared with the same calorie reduction, the time window brings nothing. And the warnings circulating on this topic come from short experiments in young women with regular cycles. What remains are two concrete risks that have little to do with the clock.

Key points

  • 4 independent meta-analyses reach the same result: compared with equal calorie reduction, a difference of 0.4 kilos, with a confidence interval extending to 0.1 kilos in the opposite direction.
  • Of 28 randomized studies on intermittent fasting versus calorie reduction, 19 are mixed, 1 is men-only and 8 are women-only — none of them unambiguously after menopause.
  • No fewer than 2 meta-analyses of exclusively female cohorts, with 13 studies and 612 participants and with 22 studies and 1,287 participants, report menopausal status nowhere.
  • The largest long-term study of alternate-day fasting, 100 participants over 1 year and 86 percent women, listed perimenopause as an exclusion criterion.
  • Specifically for this group there are 7 small studies with a combined total of just over 400 women, the longest over 12 weeks, none with a hard endpoint and none with a bone measurement.
  • The widely cited threshold of 30 kilocalories per kilo of fat-free mass comes from 2 experiments of 5 days each, each in 29 young women with regular cycles.
  • In the one-year study on alternate-day fasting, 38 percent dropped out, versus 29 percent under daily calorie reduction and 26 percent with no intervention at all.

Where the data stop

On the question of whether an eating window changes bone density in women after menopause, there is not a single randomized trial — so not reassuring data, but none at all. Of 8 studies that measured bone at all, none had it as the main question, all were mixed, all used whole-body measurement, none ran longer than 6 months. The best-known warning finding answers a different question anyway: in 101 women after menopause, the heavily restricted group lost 1.2 kilos more lean mass and 0.017 grams per square centimeter more hip bone density, and the disadvantage was still there after 3 years. That was continuous calorie reduction, not intermittent fasting.

Supported, by contrast, are two things unrelated to the clock. With insulin and the older insulin-releasing diabetes tablets, fasting becomes a medication-dosing problem; in the largest 5:2 study in type 2 diabetes, the medication protocol had to be changed after the 38th person. And on the link with disordered eating there are only cross-sectional studies and one cohort, all self-report in young people, with no statement about the direction.

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Published on October 10, 2026.

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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-09-19.