Time restricted feeding (TRF) is a form of intermittent fasting that involves confining the period of eating to 4-8 h and water fasting the rest of the day. Recent findings suggest that 8-h TRF produces modest weight loss after 12 weeks. What remains unknown however, is whether shorter feeding windows during TRF (such as 4-h or 6-h) can produce even greater weight loss in obese adults.


Adults with obesity (n = 23) were randomized to 1 of 3 interventions for 8 weeks: 4-h TRF (ad libitum eating between 3:00 to 7:00 pm, water fasting between 7:00 to 3:00 pm); 6-h TRF (ad libitum eating between 1:00 to 7:00 pm, water fasting between 7:00 to 1:00 pm); or control (ad libitum food intake with no timing restrictions).


Body weight decreased similarly in the 4-h TRF group (-3.3 ± 0.5%) and 6-h TRF group (-2.6 ± 0.5%) relative to controls over 8 weeks (P < 0.001). Fat mass and visceral fat mass also decreased in the 4-h TRF and 6-h TRF groups versus controls. Lean mass, blood pressure, LDL cholesterol, HDL cholesterol, triglycerides, fasting glucose, fasting insulin, HOMA-IR, and HbA1c were not significantly different from controls after 8 weeks.


These preliminary findings suggest that 4-h TRF and 6-h TRF produce similar degrees of weight loss (~3%) in adults with obesity. Neither diet had any effect of metabolic disease risk indicators in this pilot trial.