Researchers at the University of California San Francisco say your body has a food clock that keeps your metabolism working at a certain pace.
When you change the type of food you eat and start eating at different times -- like during the holidays -- your food clock is thrown off schedule -- which causes weight gain.
Researchers have pinpointed the mechanism that resets the food clock every time your eating habits change.
One day experts hope to use this information to help people prevent weight gain.
In the meantime, you can begin to eat normal portions at your normal time to reset that food clock.