Insulin Strategies for Managing Glycemia With Dietary Fat and Protein in Type 1 Diabetes

In a paper published in Diabetic Medicine, researchers outline evidence-based strategies for managing the glycemic impact of meals containing at least 30 grams of carbohydrate, mixed with fat and protein, in patients with type 1 diabetes. The paper describes strategies for increasing insulin dose, modifying the insulin delivery pattern, altering insulin dose split, and varying insulin delivery timing.

The strategies were identified in a systematic literature review of randomized controlled studies that measured the effects of insulin dosing interventions for fat and protein or fat meals in relation to postprandial blood sugar. Studies were required to report at least 1 glycemic outcome: mean glucose, area or incremental area under the glucose curve, hypoglycemic events, or the duration of time spent in a postprandial glucose target range.

Findings from the review highlight the glycemic benefit of an additional initial insulin dose increase equal to 24% insulin-to-carbohydrate ratio (ICR) for fat and fat and protein meals containing at least 19 to 50 grams of carbohydrate. The researchers suggest the insulin dose can be further increased to a maximum of 75% ICR with corresponding titration according to the patient’s postprandial glucose response. The researchers added that the findings suggest postprandial capillary blood glucose testing at 1.5 hours, 3 hours, and 6 hours is recommended in cases where continuous glucose monitoring is not used or available.

Additionally, the researchers noted that studies examining the additional insulin dose required for fat and fat and protein in control meals supports an increase in insulin dose of 30% ICR for carbohydrate meals containing more than 30 grams of fat or more than 15 grams of fat with more than 25 grams of protein.

The researchers explained that the percentage of upfront insulin may differ among patients, given the individualized nature of fat and protein sensitivity as well as the total meal nutrient composition. As such, meals that contain a higher level of fat compared with protein may mean patients will require less upfront insulin, such as 50% to 70% ICR. In contrast, meals with higher protein compared with fat may mean patients will require more upfront insulin, such as more than 70% to 125% ICR.

A total of 3 studies in the review examined the optimal split of meal insulin with a combination bolus for a high-protein, high-fat meal as well as a range of high-fat meals in patients with type 1 diabetes treated with insulin pump therapy. Based on these studies, the researchers suggest there is enough evidence to support combination but not extended boluses compared with standard boluses. In addition, the researchers suggest the evidence advises an upfront 70% ICR dose to be delivered 15 minutes before the meal. The recommended duration of the extended bolus should be between 1 hour and 3 hours.

The systematic literature review was limited by the reliance on evidence from some studies that contained fewer than 20 participants. Additionally, 2 studies in this review had only a 3-hour postprandial monitoring period, thereby failing to assess the late and sustained glycemic impact of protein and fat starting at the 3-hour mark.  

The researchers noted “that adjusting insulin to carbohydrate alone can be challenging, and that implementation of these findings into clinical care may only be possible with the introduction of novel decision-making support tools.”

Reference

Smith TA, Marlow AA, King BR, Smart CE. Insulin strategies for dietary fat and protein in type 1 diabetes: a systematic review. Diabet Med. Published online July 12, 2021. doi:10.1111/dme.14641