Ramadan model of intermittent fasting for 28 d had no major effect on body composition, glucose metabolism, or cognitive functions in healthy lean men.

Objectives: There has been a parallel increase in the incidence of obesity and diabetes as well as the number of daily meals. However, evidence is lacking regarding the role of intermittent fasting. The aim of this study was to determine the effects of a Ramadan model of intermittent fasting (RIF; 14 h of daytime abstinence from food and drinking) for 28 d on body composition, glucose metabolism, and cognitive function.

Methods: Ten healthy, lean men were included in a nonrandomized, crossover, intervention study. Testing was performed before a control period of 28 d, as well as before and after 28 d of RIF. Whole-body dual-energy x-ray absorptiometry, magnetic resonance imaging of the abdomen, fitness test, oral glucose tolerance test, and cognitive function tests were performed. As secondary outcome, the participants' physical activity and 72-h glycemic responses were monitored 6 d within each of the periods. Dietary intake, appetite, and mood questionnaires also were assessed.

Results: Comparing Δ differences from testing days; body mass index changes from the control period (Δ mean: 0.2 kg/m, 95% confidence interval [CI], -2 to 0.5) and the RIF period (Δ mean: -0.3 kg/m, 95% CI, -0.6 to -0.1) were significantly different (P < 0.05). Secondary outcomes within the RIF period showed an increased area under curve (AUC) for hunger accompanied by a reduced AUC for satiety (both, P < 0.05), less mean steps per day (P < 0.05), and less positive feelings in the afternoon (P < 0.01) compared with the control period. No changes were observed in any of the other evaluated parameters.

Conclusions: Free-living participants were able to comply with 14 h of daily daytime abstinence from food and drinking for 28 d with only a minor effect on body mass index and without any effects on body composition, glucose metabolism, and cognitive function.