Diet has long been believed to be an important risk factor for non-insulin-dependent diabetes. Animal studies generally support a relation between high-fat diets and development of insulin resistance.

However, conclusive epidemiologic evidence is lacking. To further investigate the role of dietary fat and carbohydrate as potential risk factors for the onset of non-insulin-dependent diabetes mellitus, current diet was assessed among a geographically based group of 1,317 subjects without a prior diagnosis of diabetes who were seen in the period from 1984 to 1988 in two countries in southern Colorado.

In this study, 24-hour diet recalls were reported prior to an oral glucose tolerance test. Persons with previously undiagnosed diabetes (n = 70) and impaired glucose tolerance (n = 171) were each compared with confirmed normal controls (n = 1,076). The adjusted odds ratios relating a 40-g/day increase in fat intake to non-insulin-dependent diabetes mellitus and impaired glucose tolerance were 1.51 (95% confidence interval 0.85-2.67) and 1.62 (95% confidence interval 1.09-2.41), respectively.

Restricting cases to diabetic persons with fasting glucose greater than 140 mg/dl and persons with impaired glucose tolerance confirmed on follow-up, the odds ratios increased to 3.03 (95% confidence interval 1.07-8.62) and 2.67 (95% confidence interval 1.33-5.36), respectively. The findings support the hypothesis that high-fat, low-carbohydrate diets are associated with the onset of non-insulin-dependent diabetes mellitus in humans.