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 PYY3-36, 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 PYY3-36 to assess their subsequent food consumption patterns, PYY3-36 levels, and glucose and insulin levels. We also investigated whether light exposure during the night would alter food consumption and PYY3-36 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 PYY3-36 during the night were more effective in reducing food consumption compared to PYY3-36 administration during the day. Constant light exposure suppressed food consumption after fasting and increased fasting PYY3-36 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 PYY3-36.
Keywords: Circadian; Constant light; Feeding behavior; PYY.