Physical activity and the metabolic syndrome - Physical Activity

Nutrition Research Newsletter, Nov, 2002 by Melinda L. Irwin, Barbara E. Ainsworth, Elizabeth J. Mayer-Davis

The metabolic syndrome is defined as a combination of three or more risk factors for cardiovascular disease (CVD) including central obesity, hypertriglyceridemia, high blood pressure, high fasting glucose, and decreased high-density liopoprotein-cholesterol (HDL-C). This syndrome is highly prevalent in the United States while approximately 24% of adults are afflicted. Weight management and achieving appropriate levels of physical activity (PA) may provide a comprehensive strategy toward prevention and/or treatment of the metabolic syndrome.

Little is known about the association between PA, fitness levels, and the metabolic syndrome in women of different ethnicities. Therefore, some researchers from Yale University investigated the association among PA. specifically moderate- and vigorous-intensity PA, maximal treadmill duration and the metabolic syndrome in a sample of African-American, Native-American and white women.

One hundred and forty-six women in the Cross-Cultural Activity Participation Study were included in the present study. The metabolic syndrome was defined as three or more of the following risk factors: waist circumference > 88 cm, blood pressure > 130/85 mm Hg, fasting glucose > 110 mg/ DL, hypertriglyceridemia (> 150 mg/dL), and HDL-C < 50 mg/ dL. PA records from four consecutive days were collected twice, one month apart, to obtain a detailed account of all PA performed. Maximal treadmill duration was determined from the subject's time to exhaustion on a treadmill graded exercise test. Women were categorized into quartiles of moderate-intensity PA, vigorous-intensity PA, and maximal treadmill duration. Blood pressure, weight, height, waist circumference were measured, while triglyceride levels and fasting glucose levels were determined.

African-American women had the highest prevalence of central obesity (53%) and hypertension (71%), whereas Native-American women had the highest prevalence of high glucose levels (20%), hypertriglyceridemia (28%), and low HDL-C (54%). The metabolic syndrome was evident in 27% of this cohort with the highest prevalence in Native-American women (37%) compared with African-American women (33%) and white women (12%). The odds of having the metabolic syndrome was 82% lower among the most active women, while the odds were 93% lower among women in the highest quartile of maximal treadmill duration (>16 min) compared with women in the lowest quartile (< 10 min). The inverse association among moderate-intensity PA, vigorous-intensity PA and maximal treadmill duration and the metabolic syndrome were similar for each ethnic group.

While the results show that all associations (moderate-intensity PA, vigorous-intensity PA, and maximal treadmill duration with the metabolic syndrome) were statistically significant, the strongest association was observed between maximal treadmill duration and the metabolic syndrome. Maximal treadmill duration, a proxy of cardiorespiratory fitness, is a more objective, yet indirect, measure of PA. One limitation of this study could be over-reporting of PA on the PA records, leading to a greater measurement error. Further studies with larger samples sizes examining the association between different types of moderate-intensity PA and the metabolic syndrome among ethnically diverse men and women are necessary to confirm the results of this study.

Melinda L. Irwin, Barbara E. Ainsworth, Elizabeth J. Mayer-Davis, et al., Physical activity and the metabolic syndrome in a tri-ethnic sample of women, Obesity Research 10(10): 1030-1037 (October 2002) [Address correspondence to Melinda L. Irwin. PhD, MPH. Department of Epidemiology and Public Health, Yale University School of Medicine PO Box 208034, New Haven, CT 06520-8034. E-mail: melinda.irwin@yale.edu]