The systematic review by Vlastaridou et al.1 addresses a critical gap in intermittent fasting (IF) research: The durability of metabolic benefits beyond 12 months. This is a valuable criterion since although IF has gained substantial popularity as an alternative to continuous energy restriction (CER), most supporting evidence derives from short-term trials. By synthesizing 15 randomized controlled trials (RCTs) with 12–24 month follow-up enrolling over 2000 participants, this review provides timely evidence regarding the sustained efficacy of IF for weight management. The central finding that IF produces comparable long-term weight outcomes to CER, aligns with recent meta-analytic evidence, however effects on body composition varied between studies. Schroor et al. reported no significant differences in body weight (weighted mean difference: −0.42 kg; 95% confidence interval CI: −0.96–0.13) or fat mass between combined IF protocols and CER, although IF was associated with slightly greater reductions in waist circumference.2 The network meta-analysis by Semnani-Azad et al., comprising 99 RCTs with 6582 participants, reinforced these findings, demonstrating that all IF strategies and CER produce comparable weight reductions versus ad libitum diets, with only alternate-day fasting showing modest superiority over CER (−1.29 kg; 95% CI: −1.99 to − 0.59).3 Long-term weight maintenance remains challenging across all dietary interventions, although most studies fail to provide information on the maintenance phase. It is well documented that approximately 30%–35% of lost weight is regained within 1 year, with approximately 50% of individuals returning to baseline weight within 5 years.4,5 Evidence from the DIRECT trial indicates that initial 6-month weight reduction is the main predictor of both long-term retention and sustained success.6 Critically, dietary adherence, regardless of the specific dietary approach, emerges as the most powerful predictor of weight loss success,7 but the majority of the trials fail to address it along with weight maintenance postintervention. Adherence data were reported in only 6 of 15 trials, and professional support intensity varied substantially. Given that adherence determines intervention success, future trials should standardize and report adherence metrics systematically. Whether IF offers particular advantages for specific populations, such as those with insulin resistance or circadian disruption, requires targeted investigation. These findings have clinical implications. The equivalence of IF and CER for long-term outcomes suggests that the choice between approaches should be guided by individual preference, lifestyle compatibility, and sustainable adherence rather than presumed metabolic superiority.8 Comprehensive lifestyle modification integrating dietary strategies with behavioral support remains foundational to obesity management.7 The present review’s finding that alternate-day modified fasting (ADMF) was the only regimen demonstrating a small beneficial weight loss versus both CER and ad libitum diets, also confirmed by others,3,9 merits attention since beyond metabolic benefits reported, observed elevations in total and LDL cholesterol with ADMF raise safety considerations warranting clinical monitoring. The mechanistic basis for these effects, whether related to circadian alignment, enhanced autophagy, or metabolic reprogramming, remains to be elucidated.10 In conclusion, results synthetized by Vlastaridou et al.1 demonstrate comparable efficacy of IF to conventional energy restriction for weight loss, however, the limited evidence on maintenance outcomes and adherence assessment represents a significant gap requiring attention. Future research should prioritize extended follow-up periods of 24 months or greater, incorporate standardized maintenance phase protocols, and evaluate adherence facilitators within real-world settings.
Emmanuella Magriplis (Tue,) studied this question.