A new systematic review and meta-analysis of 15 randomized controlled trials provides a quantitative look at the effects of intermittent fasting (IF) on overweight and obese adults. The study, which synthesized data from 758 participants, confirms that IF is an effective strategy for weight loss and improving key cardiometabolic risk factors, including lipid profiles and blood pressure ^[1]. These findings solidify IF's position as a viable, non-pharmacological intervention for metabolic health, though its effects appear to be dependent on duration and specific fasting protocol.

Key Findings

This meta-analysis pooled data from 15 RCTs comparing various intermittent fasting protocols to control diets in overweight and obese adults.

• Weight Loss: IF led to a significant average reduction in body weight of 3.73 kg (approx. 8.2 lbs) and a BMI reduction of 1.04 kg/m².
• Lipid Profile Improvement: The intervention significantly lowered total cholesterol by 6.31 mg/dL and LDL cholesterol by 5.44 mg/dL.
• Blood Pressure: Diastolic blood pressure (DBP) was reduced by an average of 3.30 mmHg. However, there was no significant effect on systolic blood pressure (SBP).
• Glycemic Control: IF did not produce statistically significant changes in fasting plasma glucose (FPG) or HbA1c in this population.
• Duration Matters: Short-term IF (≤ 12 weeks) was associated with a temporary increase in triglycerides (TG), while longer-term interventions (> 12 weeks) were required to see optimal lipid benefits.
• Protocol Differences: Subgroup analysis suggested that alternate-day fasting (ADF) was more effective than time-restricted eating (TRE) for both weight loss and LDL reduction.

The Longevity Context

The results of this meta-analysis directly address the health consequences of obesity, which is a primary driver of cardiovascular disease, the world's leading cause of mortality ^[2]. By inducing weight loss and improving cardiometabolic markers, IF targets the root causes of many age-related diseases. The observed reduction in LDL cholesterol is particularly relevant. While the absolute reduction of 5.44 mg/dL is modest, a large body of evidence from genetic, epidemiologic, and clinical studies has established LDL as a direct, causal factor in the development of atherosclerotic cardiovascular disease ^[3]. Any sustained reduction in this biomarker is a step toward mitigating long-term risk.

The benefits of IF extend beyond simple caloric restriction. The practice induces a metabolic switch from glucose-based to ketone-based energy, triggering a cascade of cellular adaptations including enhanced stress resistance, reduced inflammation, and activation of autophagy. As a comprehensive review in the New England Journal of Medicine details, these coordinated responses are thought to underpin the improvements in metabolic regulation and resilience seen with fasting protocols ^[4]. This meta-analysis provides clinical data supporting these proposed mechanisms, showing tangible improvements in human cardiometabolic health.

Actionable Protocol

Based on these findings, intermittent fasting can be implemented as a structured protocol for improving body composition and metabolic health.

1. Select a Protocol: While alternate-day fasting (ADF) showed superior results in this analysis, time-restricted eating (TRE) is often considered more sustainable for beginners. A common starting point for TRE is the 16:8 method (a 16-hour fast with an 8-hour eating window).
2. Commit to Duration: The data indicates that benefits, particularly for lipid profiles, are optimized with long-term adherence. Plan for an intervention period of at least 12 weeks to see significant metabolic shifts.
3. Prioritize Nutrient Density: The benefits of IF are maximized when the eating window is filled with nutrient-dense, whole foods. Avoid using the eating window as a license to consume ultra-processed foods, which can negate the positive effects.
4. Monitor Key Biomarkers: Track body weight, blood pressure, and a fasting lipid panel (Total Cholesterol, LDL, HDL, Triglycerides) to measure progress and adjust the protocol as needed.

Citations

1. Wang, B., Wang, C., & Li, H. (2025). 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. Nutrition Journal, 24(1), 120.
2. Powell-Wiley, T. M., et al. (2021). Obesity and Cardiovascular Disease: A Scientific Statement From the American Heart Association. Circulation, 143(21), e984-e1010.
3. Ference, B. A., et al. (2017). Low-density lipoproteins cause atherosclerotic cardiovascular disease. 1. Evidence from genetic, epidemiologic, and clinical studies. A consensus statement from the European Atherosclerosis Society Consensus Panel. European Heart Journal, 38(32), 2459-2472.
4. de Cabo, R., & Mattson, M. P. (2019). Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine, 381(26), 2541-2551.