The Effects of Isocaloric Intermittent Fasting vs Daily Caloric Restriction on Weight Loss and Metabolic Risk Factors for Noncommunicable Chronic Diseases: A Systematic Review of Randomized Controlled or Comparative Trials

Background Intermittent fasting (IF) has gained favor as an alternative regimen to daily caloric restriction (DCR). Therefore, there is a need for systematic reviews of randomized controlled/comparison trials examining the effects of isocaloric IF vs DCR on metabolic risk factors for noncommunicable chronic diseases. Objective To systematically investigate the effects of isocaloric IF vs DCR on metabolic risk factors for noncommunicable chronic diseases in adults with overweight and obesity. Methods Five online databases (PubMed, Scopus, Web of Science, Cochrane Central Register of Controlled Trials, and Google Scholar) were searched for articles published from January 2000 through April 2022. The updated Cochrane Risk of Bias Assessment tool for randomized controlled/comparison trials was used to assess risk of bias in the included studies. This review includes randomized controlled/comparison trials with matched energy intakes (isocaloric) between IF and DCR among adults with overweight and obesity with >8-week durations, that assessed risk factors related to obesity and for diabetes, cardiovascular diseases, and cancers. Results Thirteen randomized controlled/comparison trials with matched energy intakes (isocaloric) between IF and DCR were identified. The effects of IF on weight loss and metabolic risk markers of diabetes, cardiovascular diseases, and cancers were varied but generally comparable with DCR. IF (4:3 and 5:2 diets) was superior to DCR for improving insulin sensitivity in two studies. Reductions in body fat were significantly greater with IF (5:2 diet and time-restricted eating) than DCR in two studies of isocaloric diets. Conclusions With matched energy intakes, IF interventions produced similar beneficial effects for weight loss and chronic disease risk factors compared with DCR. Very limited evidence suggests that IF may be more effective vs DCR for fat loss and insulin sensitivity, but conclusions cannot be drawn based on the current evidence. Future clinical studies with larger populations and longer durations are needed for further elucidation of any potential effects of IF regimens for prevention of noncommunicable chronic diseases.