Evening is the best time to exercise. According to a research report published by the Clinical Research Center of the University of Chicago, the human biological clock plays a more important role in the body's response to exercise than previously thought. The research center studied the body's (hormone level) response to exercise in 40 men aged 30 to 40 at different times of the day. The results show that hormones, the key substances of human metabolism, have the strongest response to physical exercise in the evening and at night. Researchers at the University of Chicago said: "At night or at night, corticosteroids related to fat metabolism and thyrotropin related to muscle repair rise sharply."

For example, the researchers said that the blood test results after an hour of high-intensity exercise on the treadmill in the morning showed that the hormone level was comparable to that when staying in bed at the same time. After the same exercise from 7 pm to 2 am the next day, the hormone level is much higher than other time periods. This shows that the response of hormones in human body to exercise at different time periods is controlled by biological clock or circadian rhythm. The researchers said: "It is too early to conclude that exercising in one time period is better than exercising in another time period, but we are surprised that the hormonal response to exercise is related to the time period." "The biological clock seems to play an important role in the body's response to exercise."

In the past, experts generally thought that morning was the best time to exercise and lose weight, but the results of this study may change this view and think that evening exercise is more suitable.