With more than a third of Americans classified as obese, everyone from first lady Michelle Obama to TV news anchor Katie Couric is advocating exercise to maintain a healthy weight.

That’s great, says Dr. Eudene Harry, author of “Live Younger in 8 Simple Steps,” (www.LivingHealthyLookingYounger.com), but the benefits of exercise go far beyond fitting into those skinny jeans.

For one, it will give you younger looking, more blemish-free skin.

“The increase in circulation and perspiration that occurs with exercise delivers more nutrients to your skin while allowing impurities and waste to be removed,” says Harry, who combines years of emergency-room experience with holistic medicine in her private practice. “The result? A healthier complexion!”

She adds four more hidden benefits of a good workout:

• Natural “feel-good” chemicals: Exercise releases endorphins, the brain chemicals that boost your mood and make you feel happy, as well as relieve stress, and enhance your self-esteem and self-confidence. Exercise has also been shown to increase neurotransmitters, such as serotonin and dopamine, which gives us a natural high and allows us to sleep better.

• Constipation prevention: Exercise increases the contractions of the wall of the intestine, helping to move things along through the intestinal tract more easily, and decreasing the time it takes to pass through the large intestine. But wait an hour or two after eating before exerting yourself: Exercising too soon after a meal can divert blood flow away from the gut and toward the muscles, weakening peristaltic contractions (and slowing down the digestion process).

• Prevents brittle bones: Walking, jogging, dancing, weight training and yoga are all weight-bearing exercises that help strengthen bones. Swimming and bicycling are exercises that are considered non-weight bearing. During weight-bearing exercises, bones adapt to the impact of the weight and the pull of muscles by building more bone cells, increasing strength and density and decreasing the risk of fractures, osteopenia and osteoporosis.

• Enhanced immunity: Physical exertion increases the rate at which antibodies flow through the blood stream, resulting in better immunity against sickness. The increased temperature generated during moderate exercise makes it difficult for certain infectious organisms to survive.

Don’t overdo your exercise, or you won’t see all of these benefits, Harry says.

“Check with a physician who can advise you on the right activities and intensity level for your individual needs,” she says.

“For all the benefits of exercise, there are down sides if you go at it too vigorously for your physical condition. For instance, you can actually increase stress hormones, which can make you more vulnerable to illness, rather than building your immunity.”

About Eudene Harry, M.D.