High-Fat Diet Is Associated with Obesity-Mediated Insulin Resistance and β-Cell Dysfunction in Mexican Americans

Consumption of energy-dense, nutrient-poor foods has contributed to the rising incidence of obesity and may underlie insulin resistance and beta-cell dysfunction. Macronutrient intake patterns were examined in relation to anthropometric and metabolic traits in participants of BetaGene, a family-based study of obesity, insulin resistance, and beta-cell dysfunction in Mexican Americans. Dietary intake, body composition, insulin sensitivity (S-I), and beta-cell function [Disposition Index (DI)] were assessed by food-frequency questionnaires, dual-energy X-ray absorptiometry, and intravenous glucose-tolerance tests, respectively. Patterns of macronutrient intake were identified by using a K-means model based on the proportion of total energy intake per day attributable to carbohydrate, fat, and protein and were tested for association with anthropometric and metabolic traits. Among 1150 subjects aged 18-65 y (73% female), tertiles of fat intake were associated with greater adiposity and lower S-I, after adjustment for age, sex, and daily energy intake. Moreover, 3 distinct dietary patterns were identified: "high fat" (35% fat, 44% carbohydrate, 21% protein; n = 238), "moderate fat" (28% fat, 54% carbohydrate, 18% protein; n = 520), and "low fat" (20% fat, 65% carbohydrate, 15% protein; n = 392). Compared with the low-fat group, the high-fat group had higher age-and sex-adjusted mean body mass index, body fat percentage, and trunk fat and lower S-I and DI. Further adjustment for daily energy intake by matching individuals across dietary pattern groups yielded similar results. None of the observed associations were altered after adjustment for physical activity; however, associations with S-I and DI were attenuated after adjustment for adiposity. These findings suggest that high-fat diets may contribute to increased adiposity and concomitant insulin resistance and beta-cell dysfunction in Mexican Americans. J. Nutr. 143: 479-485, 2013.