How does exercise affect energy metabolism? The key to scientifically planning and improving weight loss results.

Factors influencing energy metabolism are complex. Research on the effects of exercise on basal metabolic rate yields inconsistent results. The continued oxidation of lactic acid and fatty acids after exercise, the energy required for the recovery of glycogen stores, and endocrine changes and increased body temperature caused by exercise can all lead to an elevated resting metabolic rate that lasts for at least 1-2 hours to over ten hours. Measurements of resting metabolic rate in humans 48-72 hours after strenuous exercise show an increase of 8%-10% compared to the resting state.

Some data report that long-term, regular exercise training can increase food intake; this view is correct to a certain extent. For example, athletes and manual laborers who regularly engage in high-intensity training consume more food than those with a sedentary lifestyle, but their body fat percentage is lower, and their weight remains stable. Excessive exercise or overtraining reduces food intake and leads to weight loss. For example, rats that frequently undergo short-duration, high-intensity acute exercise loads experience decreased appetite and reduced food intake. In reality, exercise can slightly reduce the body's food intake, while obese animals generally exhibit reduced voluntary activity, increased appetite, and refusal to engage in exercise training. Moderate-intensity, short-duration exercise has no significant effect on appetite. Increased food intake after moderate or prolonged exercise has a thermic effect, increasing total energy expenditure; however, this effect may be flawed in obese individuals, and the mechanism is unclear.

Exercise increases energy expenditure; for example, the energy expenditure of brisk walking in obese individuals can reach 300 kcal/h. If walking for 3 hours daily, energy expenditure can increase by 6300 kcal per week. Theoretically, burning 1 pound of body fat requires a 3500 kcal deficit, and 6300 kcal of energy expenditure is roughly equivalent to a weight loss of 1.8 pounds. However, in reality, weight loss is only 0.5 pounds, possibly due to other factors interfering with energy metabolism. Obese individuals, especially those with a BMI > 30, have poor exercise tolerance, possibly related to a relatively blocked insulin state, limiting the utilization of free fatty acids. The impact of exercise on body composition depends on factors such as the amount, type, and duration of exercise. The effect of insufficient exercise or short-duration exercise on increasing lean body mass is uncertain; however, long-term, regular exercise training increases lean body mass, as evidenced by the significantly lower body fat percentage of elite athletes compared to the general population. Generally, individuals who have not exercised for many years will experience an increase in lean tissue mass after increasing their exercise intensity (even with activities like jogging or running), or the increase in lean body mass may offset the loss of body fat, resulting in a stable or unchanged weight. For relatively healthy individuals (without obesity or excessive body fat), increasing lean tissue mass requires strength training, such as gymnastics, wrestling, and weightlifting, which involve significant resistance. Reports indicate that among individuals of the same height, those who engage in strength training can weigh 20%–30% more than those with a sedentary lifestyle, with almost all of this extra weight being lean tissue, thus confirming that exercise not only reduces body fat but also increases lean tissue mass.