The impact of intermittent fasting on body composition and cardiometabolic outcomes in overweight and obese adults: a systematic review and meta-analysis of randomized controlled trials

Jul 30, 2025Nutrition journal

Intermittent fasting and its effects on body fat and heart health in overweight and obese adults

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Abstract

Intermittent fasting (IF) resulted in a 3.73 kg reduction in body weight among overweight and obese adults.

IF also decreased body mass index (BMI) by 1.04 kg/m² and improved lipid profiles by reducing total cholesterol (TC) and low-density lipoprotein (LDL) levels.
Short-term IF (≤ 12 weeks) may cause a temporary increase in triglycerides (TG), while long-term IF (> 12 weeks) appears to optimize lipid metabolism benefits.
Diastolic blood pressure (DBP) was significantly reduced by 3.30 mmHg, though no significant changes were observed in systolic blood pressure (SBP), fasting plasma glucose (FPG), or hemoglobin A1C (HbA1c).
Alternate day fasting (ADF) showed superior results in weight loss and LDL improvement compared to time-restricted eating (TRE).
The metabolic effects of IF are time-dependent, indicating the need for personalized regimens and adherence strategies for optimal results.

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BACKGROUND: Obesity is a global health crisis, projected to affect over 1.53 billion adults by 2035. Intermittent fasting (IF) has emerged as a potential alternative to continuous energy restriction (CER) for weight management and metabolic improvement. However, previous meta-analyses have reported inconsistent results. These knowledge gaps hinder the clinical translation of IF, and a rigorous synthesis of randomized controlled trials (RCTs) is necessary to clarify their effects on body composition and cardiometabolic health in overweight and obese populations.

METHODS: This PRISMA-guided systematic review and meta-analysis searched PubMed, Embase, and Web of Science up to March 2025. We included 15 randomized controlled trials (n = 758) comparing IF diets with control diets in overweight/obese adults. Primary outcome indicators included total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), fasting plasma glucose (FPG), hemoglobin A1C (HbA1c), systolic blood pressure (SBP), diastolic blood pressure (DBP), body weight (BW), body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR). Data were pooled using a random-effects model and analyzed in subgroups by intervention duration and IF form.

RESULTS: IF significantly reduced BW (MD: -3.73 kg, 95% CI: -5.29, -2.17) and BMI (MD: -1.04 kg/m², 95% CI: -1.39, -0.70) in overweight/obese adults, while effectively improving lipid profiles, including TC (MD: -6.31 mg/dl, 95% CI: -12.36, -0.26) and LDL (MD: -5.44 mg/dl, 95% CI: -12.36, -0.26). However, short-term IF (≤ 12 weeks) may have resulted in a temporary elevation of TG (MD: 13.22 mg/dl, 95% CI: 3.39, 23.05), whereas long-term intervention (> 12 weeks) optimized lipid metabolism benefits. In addition, IF significantly reduced DBP (MD: -3.30 mmHg, 95% CI: -5.47, -1.13) but had no significant effect on SBP, FPG and HbA1c. Subgroup analyses showed that alternate day fasting (ADF) was superior to time-restricted eating (TRE) in terms of weight loss and improvement in LDL. The findings suggest that the metabolic effects of IF are time-dependent, and that its clinical use needs to be combined with individualized regimens and long-term adherence strategies. Limitations include the short intervention period (≤ 12 weeks) and high heterogeneity of most studies, and standardized long-term trials are needed to validate the sustained benefits and safety.

CONCLUSIONS: As a non-pharmacological intervention, IF demonstrates significant value for weight management and metabolic improvement. Its advantages in adherence and metabolic regulation position it as a promising therapeutic approach. However, its long-term efficacy and safety warrant further validation through additional high-quality clinical studies. Future efforts should focus on developing precise, sustainable, and personalized IF protocols within a personalized medicine framework to achieve comprehensive cardiometabolic health optimization.

REGISTRATION: PROSPERO CRD420251036588.

Key numbers

-3.73 kg

Weight Loss

Mean difference in body weight from baseline

-1.04 kg/m²

BMI Reduction

Mean difference in body mass index from baseline

-6.31 mg/dl

Total Cholesterol Reduction

Mean difference in total cholesterol levels

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Abstract

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