Dietary Fat Acutely Increases Glucose Concentrations and Insulin Requirements in Patients With Type 1 Diabetes Implications for carbohydrate-based bolus dose calculation and intensive diabetes management

OBJECTIVE-Current guidelines for intensive treatment of type 1 diabetes base the mealtime insulin bolus calculation exclusively on carbohydrate counting. There is strong evidence that free fatty acids impair insulin sensitivity. We hypothesized that patients with type 1 diabetes would require more insulin coverage for higher-fat meals than lower-fat meals with identical carbohydrate content. RESEARCH DESIGN AND METHODS-We used a crossover design comparing two 18-h periods of closed-loop glucose control after high-fat (HF) dinner compared with low-fat (LF) dinner. Each dinner had identical carbohydrate and protein content, but different fat content (60 vs. 10 g). RESULTS-Seven patients with type 1 diabetes (age, 55 +/- 12 years; A1C 7.2 +/- 0.8%) successfully completed the protocol. HF dinner required more insulin than LF dinner (12.6 +/- 1.9 units vs. 9.0 +/- 1.3 units; P = 0.01) and, despite the additional insulin, caused more hyperglycemia (area under the curve >120 mg/dL = 16,967 +/- 2,778 vs. 8,350 +/- 1,907 mg/dL.min; P < 0001). Carbohydrate-to-insulin ratio for HF dinner was significantly lower (9 +/- 2 vs. 13 +/- 3 g/unit; P = 0.01). There were marked interindividual differences in the effect of dietary fat on insulin requirements (percent increase significantly correlated with daily insulin requirement; R-2 = 0.64; P = 0.03). CONCLUSIONS-This evidence that dietary fat increases glucose levels and insulin requirements highlights the limitations of the current carbohydrate-based approach to bolus dose calculation. These findings point to the need for alternative insulin dosing algorithms for higher-fat meals and suggest that dietary fat intake is an important nutritional consideration for glycemic control in individuals with type 1 diabetes. Diabetes Care 36:810-816, 2013