Optimal Dosage of Exercise Combined with Intermittent Fasting for Body Composition and Cardiometabolic Health in Adults: A Systematic Review and Multilevel Meta-Analysis

Why It Matters

The combined regimen offers a scalable, evidence‑based lifestyle prescription that simultaneously targets obesity and insulin resistance, key drivers of chronic disease.

Key Takeaways

• 45‑60 min sessions, four times weekly, 14‑30 weeks
• Reduces body weight, BMI, and visceral fat
• Improves fasting glucose, insulin, and HOMA‑IR
• Lipid profile improves: lower TC, TG, LDL
• Lean mass remains unchanged despite fat loss

Pulse Analysis

Interest in intermittent fasting (IF) and structured exercise has surged as clinicians search for non‑pharmacologic tools to combat obesity and metabolic disease. Prior reviews yielded mixed findings, often limited by small sample sizes and failure to account for correlated outcomes across studies. This systematic review, published in Frontiers in Nutrition, applied a rigorous three‑level random‑effects meta‑analysis to 65 RCTs, integrating over 300 effect sizes while controlling for study‑level clustering, thereby delivering a more precise estimate of the synergistic impact of EX + IF.

The pooled results demonstrate that EX + IF modestly but consistently improves body composition—reducing body mass, BMI, body‑fat percentage, waist circumference and visceral adiposity—without compromising fat‑free or lean mass. Cardiometabolic markers also respond favorably: total cholesterol, triglycerides, LDL‑C and IL‑6 decline, while fasting glucose, insulin and HOMA‑IR improve, and VO₂ max shows a small increase. Meta‑regression pinpointed an optimal dosage of 45–60 minute exercise sessions, four times per week, sustained for at least 14 weeks (total weekly volume 230–300 minutes), which maximized these benefits across heterogeneous adult populations.

For practitioners, these findings translate into a clear, evidence‑backed prescription: middle‑aged, overweight or obese adults seeking weight loss and insulin‑sensitivity gains should aim for moderate‑intensity aerobic or resistance training of 45–60 minutes per session, four sessions weekly, paired with a time‑restricted eating protocol (e.g., 16:8) for a minimum of three months. The protocol appears safe for preserving lean tissue, making it suitable for broader public‑health implementation. Future research should explore long‑term adherence, sex‑specific responses, and integration with personalized nutrition to refine guidelines further.