# Optimal dosage of exercise combined with intermittent fasting for body composition and cardiometabolic health in adults: a systematic review and multilevel meta-analysis

## TL;DR

This study finds that combining exercise with intermittent fasting helps reduce body fat and improve heart health in adults, especially when done for 45-60 minutes per session, four times a week over several weeks.

## Contribution

The study identifies optimal exercise and intermittent fasting protocols for body composition and cardiometabolic health in adults.

## Key findings

- EX + IF significantly reduces body mass, BMI, body fat, and waist circumference.
- EX + IF improves cardiometabolic markers like cholesterol and insulin resistance.
- Maximal benefits occur with 45–60 min per session, 4 sessions/week over 14–30 weeks.

## Abstract

This meta-analysis evaluated the effects of exercise combined with intermittent fasting (EX + IF) on body composition, cardiometabolic health, and muscle performance in adults and examined potential moderators. (2) PubMed, Web of Science, Embase, and the Cochrane Library were searched, and reference lists of eligible studies were screened. Effect sizes were calculated as Hedges’g. A three-level random-effects model was fitted using the metafor package in R, with moderation and meta-regression analyses conducted to identify influential factors.

Sixty-five randomized controlled trials (RCTs) including 3,293 participants (18–75 years) were included; 42% were overweight/obese and 11% were trained individuals. Compared with control conditions (exercise alone, intermittent fasting alone, or neither), EX + IF significantly reduced body mass, body mass index, body fat percentage, fat mass, waist circumference, and visceral fat, with no significant effects on fat-free mass or lean body mass. For cardiometabolic outcomes, EX + IF reduced total cholesterol, triglycerides, low-density lipoprotein cholesterol, and interleukin-6; improved fasting blood glucose, fasting insulin, and homeostasis model assessment of insulin resistance (HOMA-IR); and modestly increased VO2max. Multivariable meta-regression indicated maximal effects with 45–60 min per session, 4 sessions/week (230–300 min/week), over 14–30 weeks (cumulative training time 7,463–8,592 min).

EX + IF improves body composition in adults, benefits selected lipid and glycemic markers, and enhances cardiorespiratory fitness. Based on current evidence, it may be particularly suitable for middle-aged adults with overweight/obesity whose primary goals are weight loss and improved insulin resistance (45–60 min/session, 4 sessions/week, for ≥14 weeks).

https://www.crd.york.ac.uk/PROSPERO/view/CRD420251131430.