title: 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.
abstract: 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.
  
  
  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.
authors.affiliation: Joslin Diabetes Center, Boston, Massachusetts, USA. howard.wolpert@joslin.harvard.edu
authors.forename: Howard A
authors.initials: HA
authors.lastname: Wolpert
authors.forename: Astrid
authors.initials: A
authors.lastname: Atakov-Castillo
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Smith
authors.forename: Garry M
authors.initials: GM
authors.lastname: Steil
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D018592:Cross-Over Studies; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000178:diet therapy* / Q000188:drug therapy*; D004041:Dietary Fats / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007328:Insulin / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D004041:Dietary Fats; D007328:Insulin