Intermittent Fasting versus Calorie-Restricted Diets for Weight Loss: What Works Better? Study Finds

Intermittent fasting diets appear to offer similar benefits to traditional calorie-restricted diets for weight loss and improving cardiometabolic health, according to a large analysis of clinical trial data published in The BMJ. The study also found that alternate-day fasting may offer modest advantages over other intermittent fasting methods, though researchers emphasize the need for longer trials to confirm these results.

Researchers conducted a systematic review and network meta-analysis of 99 randomized clinical trials involving 6,582 adults with an average age of 45 and average BMI of 31. Nearly 90% of participants had existing health conditions. The trials, lasting from 3 to 52 weeks, compared various intermittent fasting strategies with calorie-restricted and unrestricted diets, assessing outcomes such as weight loss and cholesterol levels.

The analysis found that all intermittent fasting strategies and continuous calorie restriction led to small reductions in body weight compared to an unrestricted diet. Alternate day fasting was the only approach that showed a slight benefit over calorie restriction, with a mean additional weight loss of 1.29 kg. However, this did not meet the clinically significant threshold of 2 kg set by the authors.

Alternate day fasting was also associated with modest improvements in total and “bad” cholesterol compared to time-restricted eating, though no differences were found for blood sugar or “good” cholesterol levels.

The authors acknowledge limitations including short trial durations and varying quality, but highlight that this is one of the first reviews to compare all strategies in a comprehensive model. “The current evidence provides some indication that intermittent fasting diets have similar benefits to continuous energy restriction,” they conclude.

Reference: Semnani-Azad Z, Khan T A, Chiavaroli L, Chen V, Bhatt H A, Chen A et al. Intermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials BMJ 2025; 389 :e082007 doi:10.1136/bmj-2024-082007