Effects of Four Weeks of Alternate-Day Fasting with or Without Protein Supplementation-A Randomized Controlled Trial.

Four weeks of alternate-day fasting significantly reduced body mass, fat mass, and fat-free mass.

• Body mass was reduced by 2.4 kg (p < 0.001)
• Fat mass was reduced by 1.6 kg (p < 0.001)
• Fat-free mass was reduced by 0.8 kg (p < 0.001)
• Data from all three groups were combined for analyses because interaction effects were absent
• Participants alternated between feeding days (ad libitum) and fasting days (400–600 kcal consumed between 12 and 2 PM) for four weeks

Short-term alternate-day fasting did not significantly affect fasting blood glucose or resting blood pressure.

• Blood pressure and fasting glucose levels remained unchanged (p = 0.753–0.919)
• Anthropometry, fasting blood glucose, and resting blood pressure were measured weekly throughout the four-week intervention

Protein supplementation (25 g whey protein on fasting days) did not significantly attenuate fat-free mass loss compared to the control group.

• No significant differences were detected between the control (C) and protein (P) groups for any of the measures
• Twenty-six participants were randomly assigned to the control or protein group in the follow-up randomized controlled trial
• The protein group consumed 25 g of whey protein as part of the fasting-day meal
• Interaction effects between group and time were absent, leading to combined analyses across all groups

The study targeted young Asian men with an unhealthy BMI using a specific Asian BMI threshold.

• Participants were young Asian men with a BMI ≥ 23.0 kg/m²
• Twenty participants were recruited for a single-arm trial addressing short-term ADF effects on body composition
• Body composition was assessed using bioelectrical impedance analysis at pre- and post-intervention time points

The authors concluded that future studies should explore protein or leucine supplementation throughout both feeding and fasting days to better preserve muscle mass during ADF-induced weight loss.

• Low-dose protein supplementation (25 g) confined to fasting days was insufficient to prevent fat-free mass loss
• The authors suggest protein or leucine supplementation distributed across both feeding and fasting days as a potential strategy
• The reduction in fat-free mass alongside fat mass was identified as a limitation of short-term ADF