There is a high price tag to pay for being a couch potato. The lack of exercise can adversely affect the function of the brain, heart, blood vessels, bones, liver, and the intestinal tract. An inactive person is more likely to suffer from anxiety and depression, and find stress harder to manage.

Those who don’t exercise lose fitness and often become overweight, adding pounds every year. This is mostly abdominal fat, which increases the risk of heart disease and diabetes. On the other hand, one hour of brisk walking every day can cut the risk of obesity by 25 percent.

Muscles atrophy when not used. For every decade after age 50, you lose about six percent of muscle mass with a ten to 15 percent loss of strength. To build muscle, it is important to do strength training exercises at least twice a week using weights that you lift ten to 12 times per session. By gently overloading a muscle, one can make muscle fibers thicker and stronger. Strength training also helps prevent bone loss.

Inactivity also diminishes insulin sensitivity, leading to elevated blood sugar levels. Regular exercise can reverse these trends. In a large study, every hour per day watching television increased the risk of diabetes 14 percent. On the other hand, every hour per day of brisk walking decreased the risk 34 percent. Unfortunately, diabetes is no longer just a middle-age disease. Because of the sedentary lifestyle of American children, we are increasingly seeing diabetes among youth.

Inactivity also raises the risk of cancer. Men and women who are physically active can reduce their risk of colon cancer by 30 to 40 percent. Regular exercise also appears to lower the risk of breast cancer by about 20 percent.

Older people who are not physically active are at a greater risk for cognitive decline and dementia. In animal studies, the brains of physically active mice had more nerve connections and a better oxygen flow. Elderly people who exercised three or more times a week were 32 percent less likely to be diagnosed with dementia over the next six years than those who exercised fewer than three times a week.

Inactivity also increases the risk of cardiovascular disease. Exercise improves heart function and increases flexibility of blood vessels and decreases blood pressure. Exercise also decreases the risk of blood clots. Active persons are 25 percent less likely to have a stroke, and 50 percent less likely to be diagnosed with heart disease than their sedentary counterparts.

To achieve the best health benefits, one needs at least 30 minutes a day of moderate-intensity exercise, such as brisk walking and cycling. As a bonus, regular exercise boosts the immune system and reduces the risk of upper respiratory tract infections.

Winston Craig is a professor of nutrition at Andrews University.

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Inactivity increases the risk of heart disease, cancer, diabetes, and cognitive decline.

Strength training exercises build muscle and prevent bone loss.