BACKGROUND: The National Cholesterol Education Program (NCEP) recommends a 
low-saturated-fat, low-cholesterol diet, with weight loss if indicated, to 
correct elevated plasma cholesterol levels. Weight loss accomplished by simple 
caloric restriction or increased exercise typically increases the level of 
high-density lipoprotein (HDL) cholesterol. Little is known about the effects on 
plasma lipoproteins of a hypocaloric NCEP diet with or without exercise in 
overweight people.
METHODS: We tested the hypothesis that exercise (walking or jogging) will 
increase HDL cholesterol levels in moderately overweight, sedentary people who 
adopt a hypocaloric NCEP diet. We randomly assigned 132 men and 132 women 25 to 
49 years old to one of three groups: control, hypocaloric NCEP diet, or 
hypocaloric NCEP diet with exercise. One hundred nineteen of the men and 112 of 
the women returned for testing after one year.
RESULTS: After one year, the subjects in both intervention groups had reached or 
closely approached NCEP Step 1 dietary goals and reduced their mean body fat 
significantly (range of reduction in mean fat weight, 4.0 to 7.8 kg). Weight 
loss on the NCEP diet alone did not significantly change HDL cholesterol levels 
in either the men or the women as compared with the subjects in the control 
group. Plasma levels of HDL cholesterol increased significantly more in the men 
who exercised and dieted (mean [+/- SE] change, +13 +/- 3 percent) than in the 
men who only dieted (+2 +/- 3 percent, P less than 0.01) or the men who acted as 
controls (-4 +/- 2 percent, P less than 0.001). HDL cholesterol levels remained 
about the same in the women who exercised and dieted (+1 +/- 2 percent); they 
were higher than in the women who only dieted (-10 +/- 3 percent, P less than 
0.01), but not higher than in the controls (-3 +/- 3 percent).
CONCLUSIONS: Regular exercise in overweight men and women enhances the 
improvement in plasma lipoprotein levels that results from the adoption of a 
low-saturated-fat, low-cholesterol diet.