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Life sciences · Journal article
Frontiers in Nutrition · September 7, 2026
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This retrospective cohort of 109 overweight/obese Chinese adults documents linear reductions in weight, body fat percentage, and visceral adipose tissue over 4 weeks of 5:2 fasting, with a modest concurrent decline in lean mass. Sex-specific associations were identified (weight loss correlated with baseline muscle mass and BMR in females but not males), but the authors explicitly state these are observational and hypothesis-generating findings from which causality cannot be inferred.
Retrospective cohort study. 109 overweight/obese adults (28 men, 81 women) from China undergoing 4-week 5:2 fasting with weekly monitoring. Intervention: 5:2 intermittent fasting regimen (5 days of unrestricted eating + 2 days of strict calorie restriction) for 4 weeks. n = 109. China (specific centre(s) not stated).
Both sexes exhibited linear reductions in weight, body fat percentage, and visceral adipose tissue (p < 0.05) Modest decline in lean mass occurred during the intervention Weight loss correlated with baseline muscle mass (r² = 0.060, p = 0.027) and basal metabolic rate (r² = 0.059, p = 0.029) in females only
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The findings suggest that 5:2 fasting produces multi-parameter improvements in adiposity, but the concomitant lean mass reduction warrants attention in clinical counseling. Sex-specific baseline characteristics (muscle mass and BMR in females) may predict weight loss response, potentially informing personalized dietary strategies, but these are preliminary associations requiring prospective validation.
Retrospective cohort study with modest sample size and no comparator group, providing exploratory temporal data on physiological changes during 5:2 fasting but insufficient to establish causal effects or clinical utility.
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Quoted from the source exactly as published.
The findings suggest that 5:2 fasting produces multi-parameter improvements in adiposity, but the concomitant lean mass reduction warrants attention in clinical counseling. Sex-specific baseline characteristics (muscle mass and BMR in females) may predict weight loss response, potentially informing personalized dietary strategies, but these are preliminary associations requiring prospective validation.
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Background The 5:2 intermittent fasting regimen (5 days of unrestricted eating + 2 days of strict calorie restriction) has been widely adopted as a weight management strategy. However, the short-term temporal changes in body composition and its sex-specific effects on body composition remain unclear. Particularly, the relationship between weight loss and lean body mass during the weight reduction process has not been sufficiently studied. Methods This retrospective cohort analyzed serial body composition data from 109 overweight/obese adults (28 Men/81 Female; age 31.4 ± 7.5 vs. 34.4 ± 9.9, p = 0.193) undergoing 4-week 5:2 fasting with weekly monitoring. Exclusions: age <18y or ≥60y, treatment <4 weeks, or irregular follow-up. Results Both sexes exhibited linear reductions in weight, body fat percentage, and visceral adipose tissue ( p < 0.05). A modest decline in lean mass occurred, indicating that muscle preservation deserves attention in future studies. Weight loss correlated with baseline muscle mass ( r 2 = 0.060, p = 0.027) and basal metabolic rate (BMR; r 2 = 0.059, p = 0.029) in female, whereas no such associations were found in males ( p > 0.05). Age showed no significant association with outcomes ( p > 0.05). Conclusion The 5:2 regimen induces controlled multi-parameter improvements in adiposity metrics, with a concomitant trend toward lean mass reduction that merits attention. Baseline muscle mass and BMR were significant correlates of weight loss in females, suggesting that muscle-centric strategies may be particularly relevant for this subgroup. In males, weight loss appeared to be primarily associated with energy intake regulation rather than baseline body composition. These findings are observational and hypothesis-generating; causality cannot be inferred. Future prospective studies are warranted to validate these sex-specific associations.
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