Haffner, Steven M.

OBJECTIVE—To examine the influence of obesity and prevention of weight gain on the incidence of type 2 diabetes. RESEARCH DESIGN AND METHODS—We examined participants in the San Antonio Heart Study, a prospective population-based study of Mexican Americans and non-Hispanic whites residing in San Antonio, Texas. BMI was stratified into four categories: normal (<25 kg/m2), overweight (≥25 kg/m2 and <30 kg/m2), obese (≥30 kg/m2 and <35 kg/m2), and very obese (≥35 kg/m2). The number and proportion of incident cases prevented by targeting each BMI category were estimated. In addition, we calculated the decrease in risk of developing type 2 diabetes associated with weight gain prevention across both the BMI and age spectra. RESULTS—Preventing normal individuals from becoming overweight would result in the greatest reduction in incidence of type 2 diabetes. This would result in a 62 and 74% reduction in the incidence of type 2 diabetes in Mexican Americans and non-Hispanic whites, respectively. Preventing the entire population from gaining, on average, 1 BMI unit would result in a reduction in incidence of type 2 diabetes of 12.4 and 13.0% in Mexican Americans and non-Hispanic whites, respectively. CONCLUSIONS—The majority of cases of type 2 diabetes were in individuals who were overweight or mildly obese with a family history of type 2 diabetes. Public health resources should be directed toward the prevention of weight gain among normal and overweight individuals in order to prevent the maximum number of cases of type 2 diabetes.

OBJECTIVE—To compare the incidence of type 2 diabetes between low-income Mexican-Americans residing in San Antonio, Texas, and low-income residents in Mexico City, Mexico. RESEARCH DESIGN AND METHODS—Using data from the San Antonio Heart Study and the Mexico City Diabetes Study, we compared the incidence of type 2 diabetes in 35- to 64-year-old low-income Mexican-American residents of San Antonio with similarly aged low-income residents of Mexico City. Because of the different follow-up times in the two studies, Poisson regression was used to compare the rates of diabetes. Potential risk factors for diabetes were also analyzed to determine whether they explained or contributed to a difference in incidence. RESULTS—The age- and sex-adjusted incidence of type 2 diabetes was significantly higher in San Antonio (RR 2.01) compared with Mexico City. This difference was seen primarily in the oldest age group (55–64 years of age) and remained statistically significant after adjusting for a number of diabetes risk factors, including demographic, anthropometric, and metabolic variables. Follow-up rates were similar in both cities. CONCLUSIONS—We conclude that there was a higher incidence of type 2 diabetes in San Antonio than in Mexico City, and that difference occurred primarily in individuals in the oldest age group. The potential mediating factors we examined did not account for this difference. Other factors, such as exercise and diet, which were not available for analysis in this study, in addition to a cohort effect, may have contributed to the difference in incidence of type 2 diabetes in the two cities. In addition, there was no evidence of a higher case fatality among diabetic individuals from Mexico City compared with San Antonio.