The timing of fasting leads to different levels of food consumption and PYY3–36 in nocturnal mice

Purpose The daily circadian cycle is known to modulate both feeding behavior and metabolism. As such, the timing of food consumption can play a role in regulating overall health. The purpose of this study is to determine whether fasting at different times of the day alters subsequent food consumption and levels of PYY 3–36 , a hormone secreted after a meal which inhibits appetite. Methods Separate groups of mice were fasted at different times of the day: (1) start of the day, (2) middle of the day, (3) start of the night, and (4) middle of the night, and either injected with vehicle or PYY 3–36 to assess their subsequent food consumption patterns, PYY 3–36 levels, and glucose and insulin levels. We also investigated whether light exposure during the night would alter food consumption and PYY 3–36 levels after fasting. Results Mice fasted during the start of the daytime exhibited increased food consumption post-fast compared to mice fasted during the night. Injections of PYY 3–36 during the night were more effective in reducing food consumption compared to PYY 3–36 administration during the day. Constant light exposure suppressed food consumption after fasting and increased fasting PYY 3–36 levels. Conclusions These results indicate that mice exhibit distinct food consumption patterns after being presented with a fast at different times of the day. Light exposure also modulates both food consumption after a fast and levels of PYY 3–36 .