Childhood obesity is a growing global concern,and physical exercise may help decrease some of the effects of childhood and adult obesity. Frequent and regular physical exercise boosts the immune system and helps prevent the "diseases of affluence" such as heart disease, cardiovascular disease, Type 2 diabetes, and obesity.
Physical exercise is any bodily activity that enhances or maintains physical fitness and overall health and wellness. It may also help prevent depression, help to promote or maintain positive self-esteem, improve mental health generally, and can augment an individual's sex appeal or body image, which has been found to be linked with higher levels of self-esteem. Health care providers often call exercise the "miracle" or "wonder" drug—alluding to the wide variety of proven benefits that it can provide. It is performed for various reasons, including strengthening muscles and the cardiovascular system, honing athletic skills, weight loss or maintenance, and merely enjoyment.
Some individuals will as much as double their oxygen uptake, while others can never augment endurance there is tremendous variation in individual response to training; where most people will see a moderate increase in endurance from aerobic exercise. Not everyone benefits equally from exercise. This genetic variation in improvement from training is one of the key physiological differences between elite athletes and the larger population. Studies have shown that exercising in middle age leads to better physical ability later in life. Muscle hypertrophy from resistance training is primarily determined by diet and testosterone however.