OBJECTIVE To evaluate whether fat quality, in the context of meals with high– (HGI) or low–glycemic index (LGI), influences postprandial blood glucose (PPG) response in patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS According to a randomized crossover design, 13 patients with type 1 diabetes on insulin pump consumed two series (HGI or LGI) of meals with the same carbohydrate quantity while differing for amount and quality of fat: 1) low in fat (“low-fat”), 2) high in saturated fat (butter), or 3) high in monounsaturated fat (extravirgin olive oil) (EVOO). Premeal insulin doses were based on insulin–to–glycemic load ratios. Continuous glucose monitoring was performed and 6-h PPG evaluated.

RESULTS PPG was significantly different between HGI and LGI meals (P = 0.005 for time × glycemic index interaction by repeated-measures analysis [RMA]), being significantly higher during the first 3 h after the HGI meals with a later tendency to an opposite pattern. In the context of HGI meals, PPG was significantly lower after EVOO than after low-fat or butter (P < 0.0001 for time × meal interaction by RMA), with a marked difference in the 0- to 3-h glucose incremental area under the curve between EVOO (mean ± SD 198 ± 273 mmol/L × 180 min) and either low-fat (416 ± 329) or butter (398 ± 355) (P < 0.05). No significant differences were observed in PPG between the three LGI meals.

CONCLUSIONS Carbohydrate quality of a mixed meal influences shape and extent of PPG. Besides, using EVOO in an HGI meal attenuates the early postprandial glucose response observed when this meal is consumed with either low-fat or butter. Therefore, an optimal prandial insulin administration would require considering, in addition to the quantity of carbohydrates, the quality of both carbohydrate and fat.