16:8 Time-Restricted Eating in Adults 65–74: What a Small RCT Found

A promising result for older men, with a major asterisk

For adults in their late sixties and early seventies, fasting advice often outruns the evidence. A six-week randomized trial found that 16:8 time-restricted eating reduced visceral fat by 0.54 liters in overweight men aged 65-74. The same intervention produced weight loss in women of the same age, but did not significantly reduce their visceral fat or waist circumference. That split is the finding worth paying attention to-and the reason nobody should treat this study as a universal fasting prescription.

Visceral fat sits around internal organs and differs from the fat under the skin that you can pinch. It matters metabolically, but a change in a body-composition estimate is still a surrogate outcome, not proof that fasting prevents diabetes, heart attacks, disability, or death. The trial offers a useful signal in a group that fasting research often overlooks. It does not settle what 16-hour daily fasts do over months or years in real-world adults with chronic disease and medication lists.

What the six-week trial actually tested

In a 2023 randomized controlled trial by Domaszewski et al., 116 overweight adults aged 65-74 were assigned to either 16:8 time-restricted eating or their habitual diet for six weeks. The fasting group ate between noon and 8 p.m. and fasted from 8 p.m. until noon the next day. The researchers assessed body composition with a SECA mBCA 515 bioelectrical-impedance device.

Among men, the intervention was associated with statistically significant reductions in body weight of 1.8 kg (p=0.03), visceral-fat volume of 0.54 L (p≤0.001), and waist circumference of 2.9 cm (p≤0.015). Women lost 1.3 kg on average, also statistically significant (p=0.03), but the study found no statistically significant change in visceral-fat volume or waist circumference for women.

Adherence was unusually high: more than 98% in men and more than 99% in women. That makes simple noncompliance an unlikely explanation for the women's null result. It does not, however, prove that older women biologically fail to respond to 16:8 eating. The study divided 116 participants across sex and treatment groups, leaving roughly 28 or 29 people per subgroup. It was not prospectively powered to establish sex-specific differences. A small subgroup can generate a false-positive finding, a false-negative finding, or both.

The defensible reading is narrow: in this trial, older men lost estimated visceral fat during six weeks of 16:8 eating; older women did not show a statistically significant change in that endpoint.

Weight loss is not the same as visceral-fat loss

It is tempting to compress the result into "fasting works" or "fasting fails in women." Neither statement fits the data. Women in the trial did lose weight, while their estimated visceral-fat volume and waist circumference did not change significantly. Those are different endpoints, and they can move differently over six weeks.

The sex difference has a plausible biological context, but not a proven mechanism. An observational study in elderly women by Buscemi et al. reported high visceral adiposity in postmenopausal women and found that appendicular muscle mass independently predicted impaired glucose metabolism. That research does not test time-restricted eating, so it cannot explain the trial result. It only shows why regional fat distribution and muscle status deserve more attention in this population.

Nor should readers use studies in younger women to fill the gap. A randomized trial of time-restricted eating plus exercise in women with overweight or obesity reported improvements in body composition and metabolic markers, but it did not study adults aged 65-74 or isolate the same intervention. Age, exercise, baseline health, and endpoint selection can all change the result.

The muscle question remains open

The Domaszewski trial detected no change in skeletal muscle mass in either sex after six weeks. That is reassuring as far as it goes. A 2024 meta-analysis by He et al. similarly concluded that early time-restricted eating reduced body weight while preserving fat-free mass across adult randomized trials.

But neither finding establishes long-term muscle safety for people over 65. Bioelectrical impedance is less specific for visceral-fat measurement than MRI or CT, and six weeks is too short to rule out clinically meaningful loss of lean tissue over a longer period. Sarcopenia already affects an estimated 5% to 20% of adults aged 60-70 and may affect more than half of adults over 80, according to a 2022 trial report discussing sarcopenia prevalence. In older adults, weight loss without a plan for muscle preservation deserves caution.

That plan usually means more than narrowing the clock. A 2024 systematic review of whey protein with or without resistance training examined interventions intended to improve sarcopenia in older adults. It does not test time-restricted eating, but it reinforces the practical point: older adults trying to lose fat should think about protein intake and resistance training, not only fasting duration.

Fasting has not beaten ordinary calorie restriction

The broader evidence does not show that fasting has a special advantage over continuous calorie restriction for total weight loss. A 2024 systematic review and meta-analysis by Siles-Guerrero et al. found no significant superiority of fasting-based strategies over continuous calorie restriction in obese adults. It did not provide visceral-fat outcomes specifically for adults 65 and older, so it cannot erase the older-men result. It does curb the larger claim that fasting is inherently better than eating fewer calories every day.

Other fasting schedules may also produce different body-composition effects. A 2025 randomized trial by Derron et al. found that alternate-day fasting produced larger reductions in fat mass than 16:8 time-restricted eating in adults without obesity. That trial involved a different population, a different fasting pattern, and fat mass rather than visceral-fat volume. It shows that "intermittent fasting" is not one intervention with one predictable result.

Exercise also belongs in the comparison. A 2025 six-month trial by Rose et al. found that exercise intensity influenced body composition in healthy older adults. The available results do not isolate visceral-fat volumes in liters, so they cannot be directly compared with the 0.54-L estimate in the fasting study. Still, six months of follow-up is more informative about sustained body-composition change than six weeks.

Who was not studied

The trial enrolled overweight, otherwise healthy older adults. It does not establish safety for people with type 2 diabetes, cardiovascular disease, frailty, or multiple medications. The available older-adult TRE trials do not report bone-density outcomes, fracture risk, hypoglycemia rates, or medication-timing data. Those omissions matter when a person uses glucose-lowering drugs or antihypertensives; a 16-hour fast can affect both food intake and medication routines.

Long-term durability is also unknown. The 2022 review by Kang et al. described a literature weighted toward relatively healthy and younger adults, while the older-adult evidence remains short-term and limited in scope. A forthcoming nine-month HALLO-P trial in adults 60 and older will compare an eight-hour ad libitum eating window with in-person and remote 20% caloric restriction. Its results are not yet available, but the design addresses the question the six-week study cannot answer: whether TRE offers any meaningful advantage over conventional calorie restriction in older adults.

The practical verdict

For overweight men aged 65-74, six weeks of 16:8 time-restricted eating produced a statistically significant reduction in estimated visceral-fat volume, along with modest weight and waist loss, in one randomized trial. That is encouraging but preliminary evidence.

For women in the same age range, the current trial supports modest weight loss but does not support a claim that 16:8 eating reduces visceral fat. The subgroup was too small to prove a true sex difference, yet the evidence does not justify assuming the male result applies to women.

For either sex, fasting should not replace the boringly effective safeguards: adequate protein, resistance training, and medical review when diabetes, cardiovascular disease, frailty, or medications enter the picture. The study found a six-week signal, not a long-term treatment plan.