Time restricted feeding (TRF) reduces body weight, fat mass and improves glucose tolerance in both animals and humans. This study examined the effects of 10-hours of food provision when it was initiated at lights off (zeitgiber ZT12) or after a 4-hour phase delay (akin to breakfast skipping) in mice fed chow or high fat diet (HFD).
Eight-week old C57BL6 male mice (N=192) were provided with standard laboratory diet (SLD) or HFD (43% calories from fat) for 4-weeks before randomisation to 1 of 3 groups for a further 8-weeks: ad libitum (AL); 10-hr TRF initiated at ZT12 (TRFe); 10-hr TRF initiated at ZT16 (TRFd). An oral glucose tolerance test (1g/kg body weight, N=7-8/group), body composition by echoMRI (N=6/group) and metabolic monitoring over 24 hours (Promethion system, N=4-6/group) were carried out before tissue harvest at 6 time points (ZT0,4,8,12,16 &20, n=5-6/time point). Statistics were performed by 2-way ANOVA.
A diet by group interaction was observed for body weight (P<0.001) and % fat mass (P<0.001). In SLD mice, body weight was higher in AL vs TRFe (P=0.004), but this was not significant for % fat. In HFD mice, body weight and % fat were higher in AL vs TRFe and TRFd (P≤0.002) and in TRFd vs TRFe (P≤0.01). A diet by group interaction was observed in fasting glucose (P=0.003). In SLD mice, fasting glucose was not different between groups. In HFD mice, fasting glucose was higher in AL vs TRFe and TRFd (P≤0.001). Diet and group effects were observed in glucose tolerance (both P<0.001), but there was no interaction (P=0.08). TRFe and TRFd mice displayed improved glucose tolerance vs AL (P<0.01), with no difference between them.
Delaying initiation of TRF reduced the effect of this intervention on body weight and fat mass, particularly in HFD mice. However, delaying TRF did not affect improvements in glucose tolerance. Given hunger is lowest in the biological morning in humans, further exploration of delaying TRF to increase patient acceptability is warranted.