Weight Loss
Exercise burns calories and can help individuals fight obesity. If caloric intake remains constant, regular workouts lead to weight loss. Be forewarned, however, that the pounds won't melt off magically. It takes 35 miles of walking or jogging to consume the calories in one pound of fat. Effective weight loss means a long-term commitment to a regular program of vigorous exercise. One recent study indicated that for obese patients, a few daily sessions for as short as 10 minutes each was effective in helping the patients adhere to an exercise program. Abdominal crunches may help replace abdominal fat with muscle. To perform this exercise, the individual lies on the back with the head and shoulders raised; he or she contracts the stomach muscles, curling the torso slightly forward. Abdominal fat is a particular danger to the heart, although it is unknown whether doing crunches will specifically protect against heart disease. Swimming is less effective than walking or cycling in reducing body fat, but overall regular aerobic exercise is a good way to shed pounds. Contrary to popular belief, exercise does not increase appetite in people who want to lose weight; oddly enough, however, exercise improves appetite in people who are already lean.
People should be warned that without dieting, weight loss may be minimal with exercise alone, because dense muscle mass replaces fat as the body gets more fit. Nonetheless, a fit body will look more toned and be healthier.
Psychological and Emotional Benefits
Aerobic exercise is linked with improved mental vigor, including reaction time, acuity, and math skills. Exercising may even enhance creativity and imagination. According to one study, older people who are physically fit respond to mental challenges just as quickly as unfit young adults. (Stretching and weight training appear to have no such effects.) Both aerobic and nonaerobic workouts have been shown to reduce depression. According to one study, exercise was as effective for improving mood in people with clinical depression as some common forms of psychotherapy. Either brief periods of intense training or prolonged aerobic workouts can raise levels of important chemicals in the brain, such as endorphins, adrenaline, serotonin, and dopamine, that produce feelings of pleasure, causing the so-called runner's high. One study found that teenagers who were active in sports have a much better sense of well being than their sedentary peers; the more vigorously they exercised, the better was their emotional health. In one study, regular brisk walking cut in half the incidence of sleep disturbances in people who suffer from them. It should be noted that exercise in the evening, however, can cause sleep disturbances. Rhythmic aerobic and yoga exercises may be particularly helpful for combating stress, anxiety, and sleeplessness.
Diabetes
Diabetes, particularly type 2, is reaching epidemic proportions throughout the world as more and more cultures adopt Western dietary habits. Aerobic exercise is proving to have significant and particular benefits for people with both type 1 and type 2 diabetes; it increases sensitivity to insulin, lowers blood pressure, improves cholesterol levels, and decreases body fat. Regular exercise, even of moderate intensity, improves insulin sensitivity. In fact, studies of older people who engage in regular, moderate, aerobic exercise (e.g., brisk walking, biking) lower their risk for diabetes even if they don't lose weight. Anyone on insulin or who has complications from diabetes must take special precautions before embarking on a workout program (see, What Are the Hazards of Exercise?, below).
Longevity and Aging
Exercise, even after age 50, can add healthy and active years to one's life. Studies continue to show that it is never too late to start exercising and that even small improvements in physical fitness can significantly lower the risk of death. Simply walking regularly can prolong life in the elderly. Moderately fit people, even if they smoke or have high blood pressure, have a lower mortality rate than the least fit. Resistance training is important for the elderly, because it is the only form of exercise that can slow and even reverse the decline in muscle mass, bone density, and strength. Adding workouts that focus on speed and agility may be even more protective for older people. Flexibility exercises help reduce the stiffness and loss of balance that accompanies aging.