Intermittent Fasting Cuts Weight and Improves Heart Health in Overweight Adults

Obesity affects more than half of adults globally and drives cardiovascular disease, type 2 diabetes, and metabolic liver disease. Intermittent fasting (IF) has gained traction as an alternative to continuous caloric restriction, but prior meta-analyses yielded conflicting results—particularly around lipid profiles, blood glucose, and optimal fasting protocols. This 2025 PRISMA-guided meta-analysis sought to clarify IF's effects on body composition and cardiometabolic markers in overweight and obese adults.

Researchers searched PubMed, Embase, and Web of Science through March 2025, ultimately including 15 randomized controlled trials enrolling 758 adults (BMI ≥25 kg/m²). IF modalities represented included time-restricted eating (TRE), alternate day fasting (ADF), 5:2, 4:3, and general intermittent energy restriction (IER), with durations ranging from 6 to 16 weeks. Control conditions were habitual diet or exercise-matched groups. Data were pooled using random-effects models, with subgroup analyses by intervention duration (≤12 vs. >12 weeks) and IF type.

IF significantly reduced body weight (MD: −3.73 kg, 95% CI: −5.29 to −2.17) and BMI (MD: −1.04 kg/m², 95% CI: −1.39 to −0.70). Total cholesterol fell by 6.31 mg/dL and LDL by 5.44 mg/dL. Diastolic blood pressure dropped by 3.30 mmHg, a clinically meaningful reduction. Notably, short-term IF (≤12 weeks) was associated with a transient triglyceride increase of 13.22 mg/dL, while longer interventions reversed this effect and improved lipid metabolism broadly. Systolic blood pressure, fasting plasma glucose, and HbA1c showed no significant change overall. ADF outperformed TRE for both weight loss and LDL reduction in subgroup analyses.

The findings reinforce IF as a viable non-pharmacological tool for weight and cardiovascular risk management, but also highlight important nuances. The transient TG elevation during short-term IF may reflect an adaptive metabolic shift rather than harm, potentially normalizing as ketone utilization and fat oxidation pathways mature. The lack of significant glycemic improvement may reflect the short study durations dominating the dataset and a need for longer follow-up, particularly in pre-diabetic or diabetic subgroups.

Key limitations include high heterogeneity across included studies, predominantly short intervention windows (most ≤12 weeks), varying IF protocols, and limited data on adherence and long-term safety. Most studies were underpowered for glycemic outcomes. The authors call for standardized, longer-duration RCTs with personalized IF protocols to validate sustained cardiometabolic benefits and define optimal patient profiles for each fasting modality.