After you eat, your body temperature rises to burn extra calories because your body has to break down the food by a series of chemical reactions that produce heat. After you exercise, your body temperature rises and you also use extra calories. When you are inactive after eating, you burn fewer calories than when you are active, so eating at night when you are less active is more fattening.
Researcher at Northwestern University has show that mice fed only at night gained more than twice as much weight as the mice that ate during the day (Obesity, September 2009). Both groups were fed the same high-fat food, and were equally active. By the end of the six-week study, night eaters had a 48 percent increase in body weight compared to day-feeders who had a 20 percent gain.
Risk for diabetes is also increased by eating too much in the evening. Contracting muscles remove sugar from the bloodstream without needing insulin so exercise lowers you fat holding insulin levels. Being active before eating lowers blood sugar levels the next morning (Medicine and Science in Sports and Exercise, August 2009), and exercising after eating lowers blood sugar levels after eating even more than exercising before eating (Journal of the American Medical Directors Association, July 2009). A large meal in the evening is often followed by going to bed or sitting around watching television, which can cause high rises in blood sugar, diabetes and cell damage.
Most people are more likely to be active in the afternoon (after lunch) than in the evening (after dinner). This suggests that you should eat your main meal mid-day and have a light supper.
Any type of activity clears blood sugar far better than keeping your muscles still.