Dietary Carbohydrate, a Big Mac, and Insulin Requirements in Type I Diabetes

Using the artificial (β-cell (Biostator), we determined the insulin requirements in five nonobese type I (insulindependent) diabetic subjects who received isocaloric 40 and 60% mixed-carbohydrate diets in a crossover randomized fashion for 4 days, each day consisting of four equal meals. This was followed on day 5 by a “Big Mac Attack” lunch consisting of a Big Mac, french fries, and milk shake. Insulin requirements to maintain normoglycemia were calculated for each 24-h period and for the 2 h after each meal. The mean 24-h insulin requirements to maintain normoglycemia was greater for the 60% carbohydrate diet than the 40% diet. Although the four meals were of equal size, in all patients the insulin required to cover breakfast > lunch > dinner > snack. Expressed as milliunits per kilocalorie, the amount of insulin to cover breakfast was greater for the 60% (P < .05) than the 40% carbohydrate diet and greater for breakfast than the other meals (P < .01). Insulin requirements for the Big Mac meal (43% carbohydrate) were 58% greater than for the 40% carbohydrate diet, even after correction for caloric differences. In summary, 1) increasing dietary carbohydrate from 40 to 60% results in an increased insulin requirement for meals only; 2) insulin requirements are greater in the morning than in the evening, even when meal size is constant; and 3) very large meals with high fat and carbohydrate content result in a major increase in insulin requirement. These data indicate that diet has an important impact on insulin requirements in diabetes.