The impact of central obesity as a prerequisite for the diagnosis of metabolic syndrome

Objective: To compare the prevalence of metabolic syndrome (MS) defined according to the American Heart Association (AHA)/National Heart Lung and Blood Institute (NHLBI) and the International Diabetes Federation (IDF) and to determine the effect of the presence of central obesity on the phenotype (insulin resistance and other cardiovascular risk factors) associated with MS. Research Methods and Procedures: We studied 4723 Chinese, Malays, and Asian Indians living in Singapore. Each individual was categorized according to the five criteria for MS as defined by the AHA/NHLBI and the IDF. The population was categorized according to the presence of three or more criteria and then further subcategorized according to the presence or absence of central obesity. Characteristics of each group were compared using ANOVA and the χ² test. Results: MS was present in 20.2% (IDF) and 26.9% (AHA/NHLBI) of the population. Of the population, 6.7% exhibited three or more features of MS without central obesity. Use of the IDF definition, which requires central obesity, is associated with greater insulin resistance but similar levels of other cardiovascular disease risk factors than the use of the AHA/NHLBI definition, which does not require central obesity. Discussion: In this Southeast Asian population, the IDF and the AHA/NHLBI definitions of MS identify different segments of the MS population. The IDF definition may be more appropriate for the identification of those with insulin resistance and increased risk of type 2 diabetes. In contrast, the AHA/NHLBI definition may better identify those at increased risk of cardiovascular disease.