A randomized pilot study comparing zero‐calorie alternate‐day fasting to daily caloric restriction in adults with obesity

TLDR

The study aimed to assess the safety and tolerability of zero‑calorie alternate‑day fasting (ADF) and compare its effects on weight, body composition, lipids, and insulin sensitivity to a moderate daily caloric restriction (CR) diet in adults with obesity. In an 8‑week randomized pilot, 14 participants followed ADF and 12 followed CR, with outcomes measured at week 8 and after 24 weeks of unsupervised follow‑up; 93 % of ADF participants completed the protocol and no adverse effects were reported. ADF produced weight loss comparable to CR (−8.2 kg vs −7.1 kg), with no significant differences in body composition, lipids, or insulin sensitivity at 8 weeks, and no excess weight regain at 24 weeks, though ADF showed more favorable changes in percent fat and lean mass.

Abstract

To evaluate the safety and tolerability of alternate-day fasting (ADF) and to compare changes in weight, body composition, lipids, and insulin sensitivity index (Si) with those produced by a standard weight loss diet, moderate daily caloric restriction (CR).Adults with obesity (BMI ≥30 kg/m(2) , age 18-55) were randomized to either zero-calorie ADF (n = 14) or CR (-400 kcal/day, n = 12) for 8 weeks. Outcomes were measured at the end of the 8-week intervention and after 24 weeks of unsupervised follow-up.No adverse effects were attributed to ADF, and 93% completed the 8-week ADF protocol. At 8 weeks, ADF achieved a 376 kcal/day greater energy deficit; however, there were no significant between-group differences in change in weight (mean ± SE; ADF -8.2 ± 0.9 kg, CR -7.1 ± 1.0 kg), body composition, lipids, or Si. After 24 weeks of unsupervised follow-up, there were no significant differences in weight regain; however, changes from baseline in % fat mass and lean mass were more favorable in ADF.ADF is a safe and tolerable approach to weight loss. ADF produced similar changes in weight, body composition, lipids, and Si at 8 weeks and did not appear to increase risk for weight regain 24 weeks after completing the intervention.