Subcutaneous thigh fat area is unrelated to risk of type 2 diabetes in a prospective study of Japanese Americans

Aims/hypothesis Cross-sectional research has reported a negative association between subcutaneous thigh fat (STF) and type 2 diabetes prevalence but no prospective research on this association exists using direct measurements of STF obtained from imaging studies while adjusting for other fat depots. We studied the independent associations of intra-abdominal fat (IAF), subcutaneous abdominal fat (SAF) and STF with future risk of diabetes. Methods We prospectively followed 489 non-diabetic Japanese Americans (BMI 25.0–29.9 kg/m 2 32.7%, ≥30.0 kg/m 2 5.4%) over 10 years for the development of diabetes defined by use of hypoglycaemic medication or a fasting plasma glucose ≥7.0 mmol/l or 2 h ≥11.1 mmol/l during an OGTT. STF, SAF and IAF area were measured by computed tomography scan and mid-thigh circumference (TC) by tape measure at baseline. Results Over 10 years, 103 people developed diabetes. STF area was not independently associated with the odds of developing diabetes in a univariate or multiple logistic regression model (OR for a 1 SD increase 0.8 [95% CI 0.5, 1.2]) adjusted for age, sex, BMI, IAF and SAF. The only fat depot associated with diabetes odds in this model was IAF. TC was borderline significantly associated with a lower odds of developing diabetes (0.7 [95% CI 0.5, 1.0], p = 0.052). Conclusions/interpretation Similar to other research, TC was negatively associated with diabetes risk, whereas STF was not, arguing that the negative association between TC and diabetes observed in other research is not due to STF mass. IAF area emerged as the only measured fat depot that was independently associated with type 2 diabetes risk.