Even the Pilgrims might have taken a nap after their big harvest feast, but the turkey may not be the culprit. The act of stretching the small intestine by overeating protein, fat, and sugars induces sleepiness, says biologist H. Craig Heller at Stanford University. Your body needs more energy for digestion making it less available for the brain.
The nervous system conserves energy by reducing heart rate and blood pressure, while increasing gastric juices. This effect coupled with the drowsiness caused by alcoholic beverages can make you want to nap after you eat. Relax and enjoy your holiday, but next week its back to the gym!