Sleep A 16-week exercise program (30 to 40 minutes of brisk walking or low-impact aerobics four times a week) improved the quality, duration, and ease of falling asleep in healthy older adults.1 Exercise may improve sleep by relaxing muscles, reducing stress, or warming the body.   Gallstones Active women are 30 percent less likely to have gallstone surgery than sedentary women. In one study, women who spent more than 60 hours a week sitting at work or driving were twice as likely to have gallstone surgery as women who sat for less than 40 hours a week.2   Colon Cancer The most active people have a lower risk of colon cancer — in two studies half the risk — compared to the least active people.3,4 Exercise may lower levels of prostaglandins that accelerate colon cell proliferation and raise levels of prostaglandins that increase intestinal motility. Increased motility may speed the movement of carcinogens through the colon.   Diverticular Disease In one of the few studies that have been done, the most active men had a 37 percent lower risk of symptomatic diverticular disease than the least active men.5 Most of the protection against diverticular disease--pockets in the wall of the colon that can become inflamed--was due to vigorous activities like jogging and running, rather than moderate activities like walking.   Arthritis Regular moderate exercise, whether aerobic or strength-training, can reduce joint swelling and pain in people with arthritis.6   Anxiety & Depression Getting people with anxiety or depression to do aerobic exercises like brisk walking or running curbs their symptoms, possibly by releasing natural opiates.7,8   Heart Disease In one study, men with low fitness who became fit had a lower risk of heart disease than men who stayed unfit.9 In another, women who walked the equivalent of three or more hours per week at a brisk pace had a 35 percent lower risk of heart disease than women who walked infrequently.10 Exercise boosts the supply of oxygen to the heart muscle by expanding existing arteries and creating tiny new blood vessels. It may also prevent blood clots or promote their breakdown.   Blood Pressure If your blood pressure is already high or high-normal, low- or moderate-intensity aerobic exercise — three times a week — can lower it.11 If your blood pressure isn't high, regular exercise helps keep it that way.   Diabetes The more you move, the lower your risk of diabetes, especially if you're already at risk because of excess weight, high blood pressure, or parents with diabetes. In one study, women who walked at least three hours a week had about a 40 percent lower risk of diabetes than sedentary women.12   Falls & Fractures Older women assigned to a home-based (strength- and balance-training) exercise program had fewer falls than women who didn't exercise. 13 Exercise may prevent falls and broken bones by improving muscle strength, gait, balance, and reaction time.   Enlarged Prostate (men only) In one study, men who walked two to three hours a week had a 25 percent lower risk of benign prostatic hyperplasia (enlarged prostate) than men who seldom walked.14   Osteoporosis Exercise, especially strength-training, can increase bone density in middle-aged and older people.15 Bonus: postmenopausal women who take estrogen gain more bone density if they exercise.   1 J. Amer. Med. Assoc. 277: 32, 1997. 2 N. Eng. J. Med. 341: 777, 1999. 3 J. Nat. Cancer Inst. 89: 948, 1997. 4 Ann. Intern. Med. 122: 327, 1995. 5 Gut 36: 276, 1995. 6 J. Amer. Med. Assoc. 277: 25, 1997 7 J. Psychosom. Res. 33: 537, 1989. 8 Arch. Intern. Med. 159: 2349, 1999. 9 J. Amer. Med. Assoc. 273: 1093, 1995. 10 N. Eng. J. Med. 341: 650, 1999. 11 J. Clin. Epidem. 45: 439, 1992 12 J. Am. Med. Assoc 282: 1433, 1999. 13 Brit. Med. J. 315: 1065, 1997. 14 Arch. Intern. Med. 158: 2349, 1998. 15 J. Bone Min. Res. 11: 218, 1996.