Metabolic Syndrome in Normal-weight Americans: New Definition of the Metabolically Obese, Normal-weight Individual

Objective: To determine the prevalence rates and likelihood of the metabolic syndrome and its individual components in normal-weight and slightly overweight individuals (BMI 18.5-26.9 kg/m(2)).

Research Design And Methods: There were a total of 7,602 adult participants of the Third National Health and Nutrition Examination Survey, a nationally representative cross-sectional survey. Prevalence and odds ratios (ORs) of the metabolic syndrome, defined according to National Cholesterol Education Program Adult Treatment Panel III criteria, were computed according to 2.0- to 2.5-unit increments in BMI.

Results: Depending on ethnicity and sex, the prevalence of the metabolic syndrome increased in a graded fashion from 0.9-3.0% at BMI 18.5-20.9 kg/m(2) to 9.6-22.5% at BMI 25.0-26.9 kg/m(2). Compared with men with BMI 18.5-20.9 kg/m(2), the odds for the metabolic syndrome were 4.13 (95% CI 1.57-10.87) for men with BMI 21-22.9 kg/m(2), 5.35 (2.41-11.86) for men with BMI 23-24.9 kg/m(2), and 9.08 (4.23-19.52) for men with BMI 25-26.9 kg/m(2) after controlling for age, ethnicity, education, income, physical activity, smoking status, and alcohol and total fat, saturated fat, carbohydrate, and fiber intakes. The corresponding ORs in women were 4.34 (2.08-9.07), 7.77 (3.95-15.26), and 17.34 (9.29-32.38).

Conclusions: Individuals in the upper normal-weight and slightly overweight BMI range have a relatively high prevalence and are at increased risk of having the metabolic syndrome. Therefore, screening in individuals with normal or slightly elevated BMI is important in the prevention of diabetes and cardiovascular disease.