Blame it on the trail of human evolution. During the course of millions of years, our bodies have learned to digest meals in the morning, afternoon, and evening. Weight gain is one common side effect of fighting the body's natural state. Eating more food was the reason, a common pattern among shift workers. Digestion also slows at nighttime, compounding the problem, explains Coburn.
Lack of sleep is another problem.
Your body has learned to sleep in a pattern known as your circadian rhythm. This internal clock works on a 24-hour schedule and regulates your body temperature, heart rate, hormones and sleeping patterns. Millions of years of human sleeping habits that preceded your existence now dictate a pattern of sleeping during the night and waking during the day, whether or not it's convenient for your work schedule. Since night workers are more inclined to gain weight, exercise is critical for trimming the waistline. It may also help improve the quality of sleep.