The effectiveness of 5:2 intermittent fasting compared with continuous caloric restriction in the treatment of recurrent weight gain after metabolic bariatric surgery: A non-inferiority, short-term, pilot feasibility study

INTRODUCTION: Intermittent fasting (IF) is a form of calorie restriction that has recently gained notoriety. However, there is currently no data on its effectiveness for patients with recurrent weight gain (RWG) after metabolic bariatric surgery (MBS). METHODS: A randomized non-inferiority, short-term, pilot feasibility trial was conducted to evaluate the effectiveness of 5:2 intermittent fasting (IF) (75% caloric restriction on two days per week) compared with continuous caloric restriction (CCR) (25% divided into three meals) over 12 weeks, in patients with RWG who had undergone MBS. RESULTS: Twenty patients were included (mean age 53 ± 9.5 years, body mass index 32.4 ± 3.5 kg/m²). The CCR group showed no change in weight at 12 weeks (mean difference -0.88 kg; 95% CI: -2.2 to 3.9 kg; p = 0.51), whereas the 5:2 IF group experienced an average weight loss of -1.025 kg (95% CI: -0.09 to -1.96 kg; p = 0.03). The difference between the two groups remained within the predefined non-inferiority margin of 4 kg (-0.13; 95% CI: -2.90 to 2.62). No differences in body composition or metabolic profile measurements were observed in either group compared to baseline values. The caloric intake was lower and the treatment adherence higher in the IF group. No serious adverse events occurred during follow-up. CONCLUSION: The 5:2 IF appears non-inferior to CCR at 12 weeks, suggesting it could be a promising dietary strategy for RWG. Further research with extended follow-up is essential to assess long-term feasibility, safety, and adherence. Such data will be crucial in establishing the clinical utility and practical implementation of this intervention in RWG management.