Although mealtime insulin doses are typically calculated based on carbohydrate intake alone, meals that are also high in fat and protein tend to increase postprandial glucose levels further. However, there is little evidence to guide adjustments to insulin doses in response to these other macronutrients. This study sought to determine the amount and timing of insulin required to maintain euglycaemia for 5 hours after consuming a high-fat, high-protein (HFHP) meal, using a modified glycaemic clamp technique.
Ten young people with type 1 diabetes (age 12–21 years) underwent a randomised crossover study with at least 1 week’s washout between study arms. In the control arm, participants ate a meal of pasta and tomato sauce (30 g carbohydrate, 5 g fat and 5 g protein; 182 kcal). In the HFHP arm, lean beef mince and butter were added to the meal (30 g carbohydrate, 40 g fat and 60 g protein; 717 kcal).
Participants in the HFHP arm required a mean of 5.4 units of insulin, a 95% increase in dose, to maintain euglycaemia over 5 hours postprandially compared with the control meal. On average, 46% of the insulin was required in the first 2 hours, 42% from hours 2–4 and 11% in the fifth hour. However, there was considerable variation between individuals, with extra insulin requirements ranging from 1.7 to 9.9 units (equating to a dose increase of 33% to 500%). Furthermore, some participants required the majority of the extra insulin in the first 2 hours while others required more in the second 2 hours.
The authors conclude that young people require nearly double the amount of insulin with a HFHP meal compared with a low-fat, low-protein meal with the same carbohydrate content. However, the high inter-individual variability suggests that a standardised dosing formula will be unattainable, and personalised dosing regimens, with conservative incremental dose increases of around 20% and guided by the glucose response to the previous adjustment, will be required.