Objective: To examine the association between obesity and low relative skeletal muscle mass (sarcopenia) with type 2 diabetes and poor glycemic control, and to determine whether these associations varied by ethnicity.
Design, setting, participants: Data from the Third National Health and Nutrition Examination Survey (NHANES III) was used (5,727 adults, 40-74 years of age: 26% Mexican Americans, 25% non-Hispanic Blacks, and 49% non-Hispanic Whites).
Main outcome measures: Sarcopenia was defined as a skeletal muscle [SM(kg)/ height(m2)] <1 standard deviation below the young adult mean. Obesity was defined as waist circumference >102 cm in men and >88 cm in women.
Results: The prevalence of diabetes was 40% higher in Mexican Americans than in non-Hispanic Blacks or Whites (P<.05). The lowest prevalence of obesity and sarcopenia were observed in Mexican Americans (except for obesity in women). Independent of ethnicity, subjects with a high waist circumference were more likely to have diabetes and poor glycemic control (P<.05). These associations were strongest in non-Hispanic Whites. Conversely, sarcopenia was not associated with diabetes or poor glycemic control in any ethnic group.
Conclusions: Although the prevalence of type 2 diabetes was highest in Mexican Americans, non-Hispanic Whites exhibited the highest prevalence of obesity and sarcopenia. The role of genetically based, ethnic differences in body composition and diabetes risk needs to be taken into account when developing clinical guidelines such as the waist circumference cutpoints used in this study.