Evaluating the Impact of Intermittent Fasting on Anthropometric, Cardiovascular, and Metabolic Outcomes: A Targeted Literature Review

OBJECTIVES: To evaluate the impact of intermittent fasting (IF) on anthropometric, cardiovascular, and metabolic outcomes in healthy (non-obese, obese, or lean) individuals.

METHODS: A structured search was conducted to identify randomised controlled trials (RCTs) through PubMed, US and WHO trials registries, and Google Scholar up to 15 June 2024. Title-abstract and full-text screening were performed on the EasySLR platform. Studies that evaluated the impact of IF on anthropometric, cardiovascular, and metabolic outcomes in healthy adults were included. There are different types of IF such as alternate day fasting (ADF), 5:2 fasting, time-restricted fasting, B2 fasting, weekly 1 day fasting, and intermittent very low-calorie diet therapy. For this study, we focused on ADF due to the variability in definitions of other IF types. Studies that evaluated modified ADF or ADF with any dietary/energy restrictions were excluded.

RESULTS: A total of 16 RCTs were included in this review, comprising 321 participants (predominantly female, 72.3%). Key findings include: (a) Anthropometric outcomes: Reductions were observed in fat mass (12/12 trials), body weight (13/13 trials), BMI (5/5 trials), visceral fat and waist circumference (3/3 trials). Lean mass reduced in four of five trials, with one trial showing no change from baseline; (b) Cardiovascular outcomes: Reductions were observed in total cholesterol in eight of 11 trials, increased in two trials, and remained unchanged in one trial; triglyceride reductions were observed in seven of ten trials, increased in two trials, remained unchanged in one trial; (c) Metabolic outcomes: Fasting glucose levels decreased (4/8 trials, increased in two trials, whereas remained unchanged in two trials) along with insulin levels (6/7 trials, increased in one trial).

CONCLUSIONS: ADF showed improvements across anthropometric, cardiovascular, and metabolic outcomes. These findings support the implementation of ADF as a viable lifestyle intervention for improved health. Future research should explore the long-term effects of ADF on diverse populations.