Moderate-intensity exercise that was equivalent to walking about 12 miles over an average of 170 minutes per week significantly improved features of the metabolic syndrome even without dietary modification in a study of 171 overweight adults.
Johanna L. Johnson of Duke University, Durham, N.C., and colleagues analyzed 171 overweight or mildly obese participants (80 men and 91 women) previously enrolled in the Studies of a Targeted Risk Reduction Intervention Through Defined Exercise trial. They reported their findings in the American Journal of Cardiology.
Each person was randomly assigned to 6 months of continued inactivity or one of three 6-month exercise regimens: low amount/moderate intensity (calorically equivalent to walking 12 miles a week at 40%–55% peak oxygen consumption), low amount/vigorous intensity (equal to walking 12 miles a week at 65%–80% peak oxygen consumption), and high amount/vigorous intensity (equal to walking 20 miles a week at 65%–80% peak oxygen consumption). All participants were instructed to continue their usual diet (Am. J. Cardiol. 2007; 100:1759–66).
To define metabolic syndrome, the investigators used the Education Program Adult Treatment Panel III (ATP III) criteria, in which metabolic syndrome is indicated by the presence of at least three of the following risk factors: increased waist circumference (at least 102 cm in men and 88 cm in women), increased triglyceride level (at least 150 mg/dL), decreased HDL cholesterol level (less than 40 mg/dL in men or 50 mg/dL in women), increased blood pressure (at least 130 mm Hg systolic or at least 85 mm Hg diastolic), and increased fasting glucose level (100 mg/dL or higher). The authors also devised a continuous z score of all five metabolic syndrome variables to more accurately reflect overall metabolic changes.
Participants were aged 40–65 years and were overweight or mildly obese (body mass index of 25–35 kg/m
After 6 months, improvements were seen in many metabolic syndrome parameters among both exercise groups, compared with controls.
For example, mean waist circumference dropped by 1.1 cm among all patients in the low/moderate and low/vigorous groups and by 2.6 cm for the high/vigorous group, but rose by 0.6 cm among controls. Likewise, the z score for the control group did not change over the 6 months, but it fell by 0.8 in the low/moderate group, 0.3 in the low/vigorous group, and 1.4 in the high/vigorous group.
A surprising finding, the authors noted, was that although a low amount of moderate-intensity exercise showed a significant improvement in both z score and total ATP III score at 6 months, a low amount of exercise with high intensity actually showed no significant improvement over the sedentary controls. They theorized that this may be because lower-intensity exercise relies more on fat oxidation, whereas higher-intensity exercise entails more carbohydrate oxidation.
“Our findings clearly indicate that a modest amount of moderate-intensity exercise is adequate for obtaining significant health benefits,” Ms. Johnson and her colleagues wrote. “This is an exercise prescription likely to be perceived by the general public and clinicians alike as an obtainable goal.”
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