OBJECTIVETo investigate the relative contribution of lifestyle and obesity to the risk of developing type 2 diabetes.

METHODSAll baseline survey data were based on the program Prevention of Multiple Metabolic Disorders and Metabolic Syndrome in Jiangsu Province (PMMJS) which was conducted during April 1999 to May 2004. In the baseline survey, 8685 participants were selected using multi-stage sampling method. Frem March 2006 to November 2007, 4582 participants who had been in the study for at least 5 years were included in the follow-up survey. A total of 3847 participants were followed and of them 3461 non-diabetic subjects were included in this analysis. High fat diet or not, low fiber diet or not, sedentary or not and occupational physical activity classification were defined as lifestyle variables and the incidence of type 2 diabetes at follow-up survey was defined as outcome variable. It was prospectively examined that the separate and joint association of lifestyle and obesity with the development of type 2 diabetes in subjects recruited from PMMJS, using logistic regression model.

RESULTSA total of 162 incident cases of type 2 diabetes during 6.3 years of follow-up in total 3461 participants were documented. The incidence rate was 4.7%. After adjusted for sex, age, family history of diabetes, blood pressure, lipids and fast plasma glucose, risk of type 2 diabetes increased with lighter occupational physical activity (compared with vigorous group, moderate group aRR = 2.15, 95%CI: 1.26 - 3.68; light group aRR = 2.39, 95%CI: 1.12 - 4.87), sedentary lifestyle (aRR = 2.94, 95%CI: 1.90 - 4.54), low fiber diet (aRR = 1.58, 95%CI: 1.01 - 2.53), overweight (aRR = 1.33, 95%CI: 1.01 - 1.90) and obesity (aRR = 1.59, 95%CI: 1.07 - 3.75). In joint analysis of lifestyle and obesity, the impact of sedentary lifestyle (in BMI < 25 group, aRR = 3.42, 95%CI: 1.99 - 5.86; in BMI ≥ 25 group, aRR = 2.41, 95%CI: 1.13 - 5.12) and low fiber diet (in BMI < 25 group, aRR = 1.42, 95%CI: 0.81 - 2.54; in BMI ≥ 25 group, aRR = 2.63, 95%CI: 1.15 - 6.03) on diabetes were independent of overweight and obesity. When stratified by sedentary lifestyle or low fiber diet, there was no association between overweight/obesity and diabetes risk (sedentary aRR = 2.04, 95%CI 0.87 - 4.71, non sedentary aRR = 1.21, 95%CI: 0.82 - 1.78; non low fiber diet aRR = 1.26, 95%CI: 0.87 - 1.84, low fiber diet aRR = 1.88, 95%CI: 0.80 - 4.80).

CONCLUSIONUnhealthy lifestyle, overweight and obesity independently increase the risk of type 2 diabetes. The magnitude of risk contributed by sedentary lifestyle and low fiber diet are much greater than that imparted by overweight and obesity.