Time restricted feeding (TRF) is an emerging tool that reduces body weight and improves glucose tolerance in mice. However, it is unclear if TRF is effective in humans, or if a phase delay will impact outcomes.
Males (N=15, age 55.6±11.3y, BMI 33.9±3.1kg/m2, waist circumference 115±9.5cm) were recruited into the study. Participants were fitted with continuous glucose monitors (CGM) for a 1-week baseline monitoring period followed by 2 x 1 week TRF conditions, in a randomised cross over design with a 2 week washout between conditions. Participants were instructed to consume their normal diet between 0800-1800h in the TRF-early (TRFe) condition and between 1100-2100h in the TRF-delay (TRFd) condition. No other instructions on food intake were provided. Standardised meal tests (Ensure Plus, 700 Kcal [57% carbohydrate, 28% fat, 15% protein]) were performed on Day 0 and Day 7 at 0800 (TRF-e) or 1100h (TRFd) and glucose and insulin incremental areas under the curve (iAUC) were calculated by trapezoidal rule. Statistics were performed using linear mixed modelling.
Body weight decreased during each condition by 0.8-1.2% (P<0.001), with no difference between TRFe and TRFd. Glucose iAUC was reduced by TRF (TRFe -119±39, TRFd -128±24 mmol.min/L, P=0.014), with no difference between conditions. TRF did not alter insulin iAUC (TRFe -2.96±1.37, TRFd -2.53±2.50 nmol.hour/L, P=0.09). Average daytime glucose (0800-2000h) by CGM was not different from baseline in TRFe or TRFd. However, in the TRFe condition, average early morning glucose (0200-0800h, TRFe 6.1±0.5, baseline 6.4±0.5 mmol/L, P=0.018) and early daytime (0800-1400h, TRFe 5.8±0.7, baseline 6.2±0.6 mmol/L, P=0.006) were significantly lower vs baseline.
Time restricted feeding initiated at breakfast, and after a short phase delay reduced body weight and improved glucose tolerance after 1-week. The magnitude of this improvement is greater than that seen after initiation of metformin therapy in a similar population (1).