This systematic review of the literature sought to evaluate the efficacy of various insulin dosing strategies to adjust for the fat and protein content of meals. A total of 18 studies were included in the analysis, representing 381 participants with type 1 diabetes. The conclusions drawn from the analysis were as follows.
For meals containing fat and/or protein along with at least 19 g of carbohydrate, an insulin dose increase equivalent to 24–75% of the insulin:carbohydrate ratio (ICR) is recommended, with titration based on the individual’s postprandial glycaemic response. In studies that investigated the additional insulin dose needed when fat and/or protein were added to control meals, a dose increase of 30% of the ICR is recommended for carbohydrate meals with >30 g of fat or with >15 g of fat plus >25 g of protein.
Meals with a higher fat content relative to protein may require less up-front insulin (50–70% of the ICR), whereas those with more protein than fat may require more upfront insulin (70–125% of the ICR). However, there is high inter-individual variation in sensitivity to fat and protein levels.
In individuals who self-monitor capillary blood glucose, testing at 1.5 hours, 3 hours and 6 hours postprandially is recommended.
In insulin pump users, there is evidence to support the use of combination but not extended boluses over standard boluses. An upfront dose of 70% of the ICR, delivered 15 min prior to the meal, is advised, with an extended bolus of 1–3 hours. In multiple daily injection users, the evidence regarding benefits of splitting the insulin dose was inconsistent.
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