Comparison of the association of predicted fat mass, body mass index, and other obesity indicators with type 2 diabetes risk: two large prospective studies in US men and women.

Obesity, defined by body mass index (BMI), is a well-established risk factor of type 2 diabetes, but BMI has been criticized for its inability to discriminate fat mass and lean body mass. We examined the association between predicted fat mass and type 2 diabetes risk in two large US prospective cohorts, and compared the magnitude of the association with BMI and other obesity indicators. Validated anthropometric prediction equations previously developed from the National Health and Nutrition Examination Survey were used to estimate predicted fat mass and percent fat for 97,111 participants from the Health Professionals Follow-up Study (1987-2012) and the Nurses' Health Study (1986-2012) who were followed up for type 2 diabetes. Multivariable-adjusted hazard ratios for type 2 diabetes across quintiles of predicted fat mass were 1.00, 1.96, 2.96, 3.90, and 8.38 for men and 1.00, 2.20, 3.50, 5.73, and 12.1 for women; of BMI were 1.00, 1.69, 2.45, 3.54, and 6.94 for men and 1.00, 1.76, 2.86, 4.88, and 9.88 for women. Predicted FM showed the strongest association with type 2 diabetes in men followed by waist circumference (WC), waist-to-height ratio (WHtR), predicted percent fat, BMI, Waist-to-hip ratio (WHR), and a body shape index (ABSI). For women, the strongest association was shown for WHtR, followed by WC, predicted percent fat, predicted fat mass, BMI, ABSI, and WHR. Compared to BMI, predicted fat mass demonstrated consistently stronger association with type 2 diabetes risk. However, there was inconclusive evidence to suggest that predicted fat mass is substantially superior to other obesity indicators.