Metabolic syndrome and insulin resistance significantly correlate with body mass index.

BACKGROUND: Metabolic syndrome (MetS) is a cluster of metabolic risk factors for cardiovascular disease. This study aimed to compare the prevalence of MetS and its components in different degrees of obesity in Iranian subjects.
METHODS: A total of 2309 adults were divided into four groups according to their body mass index (BMI): 1511 subjects were non-obese (BMI <30 kg/m(2)); 535 were moderately obese (BMI > or =30-<35); 176 were severely obese (BMI > or =35-<40) and 87 were morbidly obese (BMI > or =40). Fasting blood samples were obtained and plasma glucose, lipids, insulin and HbA1c were measured. The homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. The prevalence of MetS, according to the definitions of the International Diabetes Federation (IDF) and National Cholesterol Education Program Adult Treatment Panel III (ATPIII), was compared across increasing grades of BMI.
RESULTS: Prevalence of MetS gradually rose with increasing grades of obesity (p<0.001), from 31.9% in the non-obese to 69.0% in the morbidly obese according to the IDF criteria and from 31.2% to 62.1% according to the ATPIII criteria. After controlling for age and sex, one grade increase in the BMI category was associated with 2.5-3 times higher risk of MetS depending on the definition used. In addition, HOMA-IR was significantly correlated with BMI in all subjects (r=0.343, p<0.001) and in moderately (r=0.184, p<0.01), severely (r=0.147, p<0.01) and morbidly (r=0.101, p<0.05) obese participants separately.
CONCLUSIONS: MetS and its components, including high blood pressure, central obesity, hyperglycemia, IR, hypertriglyceridemia and low high-density lipoprotein-cholesterol increase in parallel with increasing obesity grades.