Effect of fat on glycaemic responses in normal subjects: a dose-response study

Adding large amounts of fat to carbohydrate reduces glycaemic responses, but the effect of varying fat across the normal range of intakes has not been studied. To test the hypothesis that fat would reduce glycaemic responses in a non-linear fashion, 12 overnight-fasted healthy subjects were studied on 5 separate days after consuming 50g available carbohydrate (white bread) plus 0, 5, 10, 20, or 40g fat (non-hydrogenated-fat margarine). Blood glucose peak rise (PR) and incremental area under the curve (iAUC) were reduced after 40g fat by 38 and 30%, respectively (p < 0.05). However, more than half these effects were seen after 5g fat. Grams fat correlated with both PR (r2 = 0.158, n = 60, p = 0.002) and iAUC (r2 = 0.080, p = 0.028), but an exponential model resulted in a better fit for iAUC (r2 = 0.084, p = 0.025) and a significantly better fit for PR (r2 = 0.244, p < 0.001). Thus, the results support the hypothesis that fat reduces glycaemic responses in a dose-dependent, but non-linear fashion. Variation of fat intake across the normal range of intakes (17–44% energy) did not significantly affect glycaemic responses.