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Insulin Dosing Requires Attention to Fat, as Well as Carbs

People with type 1 diabetes should account for the amount of fat in a meal, as well as its carbohydrate content, when calculating their insulin dose, according to new findings.

"Insulin dosing for food needs to be based not only on carbohydrate content, but on meal composition," Dr. Howard Wolpert of the Joslin Diabetes Center in Boston, an author of the study, told Reuters Health. "What it entails is a shift in the way we approach dosing for meals."

Adjustment is necessary when a meal contains at least 40 grams of fat, he added, and the adjusted dose should be spread out rather than given all at once because fat can slow gastric emptying.

Studies have shown that both fat and protein can cause postprandial hyperglycemia, Dr. Wolpert and his team note in their report, published online July 7 in Diabetes Care. But there is little data on how patients should adjust insulin to account for the amount of fat or protein in a meal, they add.

The researchers looked at differences in postprandial glycemia over a six-hour period when 10 adults with type 1 diabetes consumed a low-fat, low-protein meal (LFLP) and a high-fat, high-protein (HFHP) meal, both covered by the same insulin dose. The study participants later repeated the HFHP meal using an adaptive model-predictive bolus (MPB) of insulin. All patients were on an insulin pump.

When patients received the same insulin dose, the HFHP meal more than doubled glucose incremental area under the curve compared with the LFLP meal (27,092 vs. 13,320 mg/dL/min).

Adjusting the dose to achieve target glucose control with the HFHP meal required, on average, a 65% increase in insulin dose, although the additional amount varied widely among study participants, from 17% to 124%.

Most of the fat-related increase in glucose occurred 80 minutes after the meal.

A major limitation of past research is that investigators have assumed that people would all need the same increase in insulin when eating a higher-fat meal, Dr. Wolpert noted.

"There's huge interindividual variation in the effect of fat on people's insulin requirement, so dosing requirements need to be individualized," he said.

Protein has less of an impact on post-meal glucose, according to Dr. Wolpert, and requires insulin dose adjustment only with meals containing at least 75 grams of protein.

Dr. Wolpert is currently working on developing smartphone-based tools to provide insulin-dosing guidance based on a meal's macronutrient content.
Source: Diabetes Care 2016
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