Insulin strategies for dietary fat and protein in type 1 diabetes: A systematic review.

Smith, Tenele A; Marlow, Alexandra A; King, Bruce R; Smart, Carmel E

AIM To identify and report the efficacy of insulin strategies used to manage glycaemia following fat and/or fat and protein meals in type 1 diabetes. METHODS A systematic literature search of medical databases from 1995-2021 was undertaken. Inclusion criteria were randomised controlled trials that reported at least one of the following glycaemic outcomes: mean glucose, area under the curve, time in range or hypoglycaemic episodes. RESULTS Eighteen studies were included. Thirteen studies gave additional insulin. Five studies gave an additional 30-43% of the insulin-to-carbohydrate ratio (ICR) for 32-50g of fat and 31-51% ICR for 7-35g of fat with 12-27g of protein added to control meals. A further eight studies gave -28- +75% ICR using algorithms based on fat and protein for meals with 19-50g of carbohydrate, 2-79g of fat and 10-60g of protein, only one study reported a glycaemic benefit of giving less than an additional 24% ICR. Eight studies evaluated insulin delivery patterns. Four of six studies in pump therapy, and one of two studies in multiple daily injections showed the combination bolus and split dose, respectively were superior. Five studies examined the insulin dose split, four demonstrated 60%-125% ICR upfront was necessary. Two studies investigated the timing of insulin delivery, both reported administration 15 min before the meal lowered postprandial glycaemia. CONCLUSIONS Findings highlight the glycaemic benefit of an additional 24-75% ICR for fat and fat and protein meals. For these meals, there is supportive evidence for insulin delivery in a combination bolus with a minimum upfront dose of 60% ICR, 15 min before the meal.