Recommendations for Mealtime Insulin Adjustment According to Dietary Fat Intake

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There is a dose-dependent relationship between the amount of fat and postprandial glucose levels.

While type of dietary fat has no clear impact on glycemic response, there is a dose-dependent relationship between the amount of fat and postprandial glucose levels, according to study results published in Diabetes Care. Insulin delivery systems and dosing may need to be adjusted accordingly to better control postprandial glucose levels.

The American Diabetes Association recommends incorporating fat and protein into mealtime insulin dosing, but it is not clear how to optimally adjust the insulin dose. The goals of the current study were to determine the effect of amount and type of dietary fat on postprandial glucose levels in patients with type 1 diabetes (T1D) and the recommended adjustments of the insulin dose for different amounts of dietary fat.

The study patients were aged 18 to 65 years, diagnosed with T1D for at least 1 year, had been using an insulin pump for at least 6 months, had a hemoglobin A1c ≤8.5%, and performed an average of ≥4 blood glucose checks per day. The patients were admitted to a clinical research center on 9 to 12 occasions to complete study sessions.

The primary outcome was 5-hour incremental area under the curve (AUC) for blood glucose.

Test meals consisted of equal amounts of carbohydrate (45 g) and different types (rich in monounsaturated fatty acid, polyunsaturated fatty acid, or saturated fat) or amounts of dietary fat (0 g, 20 g, 40 g, and 60 g fat provided as avocado). For aim 1, insulin doses were calculated for each patient based on insulin/carbohydrate ratio and were delivered 15 minutes prior to consuming the meal using a 50%/50% dual-wave split over 2 hours. For aim 2, insulin doses were estimated using a Model Predicted Bolus estimator.

Of 21 adults with T1D recruited, 19 completed the study (14 women; mean age, 37.7±17.6 years; duration of insulin pump usage, 6.0±4.0 years).

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No significant differences in 5-hour incremental AUC for blood glucose were noted for different fat types. In addition, there were no significant differences in any blood glucose metrics except for coefficient of variation for fat type.

While increasing the amount of dietary fat did not have a significant effect on the overall 5-hour incremental AUC for blood glucose, there were significant dose-response relationships when comparing the early (0-2 hours; P =.004) and later (2-5 hours; P =.008) responses, as increasing dietary fat was associated with lowering the early postprandial glucose response (P <.001) and raising the late postprandial response (P =.001). Incidence of hypoglycemia also significantly decreased with greater amounts of fat.

With the optimal insulin dose, the 5-hour incremental AUC for blood glucose was significantly reduced by 50%, 35%, and 58% for the 20-g, 40-g, and 60-g fat meal, respectively (P <.001). To optimize glycemic control, mealtime insulin doses needed to be increased by up to 20% for high-fat (60 g) meals and dosed as a dual wave. According to the study results, for a 20-g fat meal, a 75%/25% insulin delivery pattern is appropriate over a period of 11/4 h; for a 40-g fat meal, a 65%/35% split is appropriate over a period of 11/4 h; and for a 60-g fat meal, a 50%/50% split is appropriate over a period of 13/4 h.

The study had several limitations, including that it was limited to participants using insulin pump therapy, had no data regarding the impact of dietary protein consumption, and excluded children and adolescents.

“This study provides clinical guidance for mealtime insulin dosing recommendations for dietary fat in T1D,” concluded the researchers.

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Bell KJ, Fio CZ, Twigg S, et al. Amount and type of dietary fat, postprandial glycemia, and insulin requirements in type 1 diabetes: a randomized within-subject trial [published online August 27, 2019]. Diabetes Care. doi:10.2337/dc19-0687/-/DC1