OBJECTIVE—The International Diabetes Federation (IDF) has proposed a new definition of the metabolic syndrome that emphasizes central adiposity as determined by ethnic group–specific thresholds of waist circumference. The objective of this study was to estimate the prevalence of this syndrome using the IDF definition among U.S. adults and to compare it with the prevalence estimated using the definition of the National Cholesterol Education Program (NCEP).

RESEARCH DESIGN AND METHODS—A total of 3,601 men and women aged ≥20 years from the National Health and Nutrition Examination Survey 1999–2002 were included in the analyses.

RESULTS—Based on the NCEP definition, the unadjusted prevalence of the metabolic syndrome was 34.5 ± 0.9% (percent ± SE) among all participants, 33.7 ± 1.6% among men, and 35.4 ± 1.2% among women. Based on the IDF definition, the unadjusted prevalence of the metabolic syndrome was 39.0 ± 1.1% among all participants, 39.9 ± 1.7% among men, and 38.1 ± 1.2% among women. The IDF definition led to higher estimates of prevalence in all of the demographic groups, especially among Mexican-American men. The two definitions similarly classified ∼93% of the participants as having or not having the metabolic syndrome.

CONCLUSIONS—In the U.S., the use of the IDF definition of the metabolic syndrome leads to a higher prevalence estimate of the metabolic syndrome than the estimate based on the NCEP definition.