Sugars and fat have different effects on postprandial glucose responses in normal and type 1 diabetic subjects

We aimed to determine the effects on glycemic responses and potential risk of hypoglycaemia in type 1 diabetic subjects of replacing half the starch in a meal with sugars, and of adding fat to the low-sugar and high-sugar meals.

We studied overnight fasted subjects with type 1 diabetes (n = 11) and age-, BMI- and ethnicity-matched controls (n = 11) using a 2 × 2 factorial design. The low-sugar/low-fat meal was 110 g white-bread. In the high-sugar/low-fat meal half the white-bread starch replaced by sugars (jam and orange juice). The high-fat meals consisted of the low-fat meals plus 20 g fat (margarine). The significance of the main effects of sugars and fat and the sugar × fat, group × sugar and group × fat interactions were determined by ANOVA. In control and diabetic subjects, respectively, high-sugar significantly reduced time to peak rise by 13% (P = 0.004) and 32% (P = 0.004; group × sugar: P = 0.01) and increased peak rise by 14% and 10% (ns). Adding fat increased time to peak rise by 17-19% in both groups (P = 0.003), reduced peak rise by 31% in normal (P < 0.001) but increased peak rise in diabetic subjects by 3% (ns) (group × fat: P = 0.022). Blood glucose nadir and occurrence of hypoglycaemia were similar among the 4 meals.

In type 1 diabetes, insulin adjustment to avoid hypoglycemia may be useful for meals in which the proportion of carbohydrate absorbed as glucose is <0.75, however the precise level which increases hypoglycaemic risk requires further research. The results suggest that people with type 1 diabetes should not be advised to add fat to meals to reduce glycemic responses.