Dietary Fat Increases Blood Glucose and Insulin Requirements

It isn't just carbohydrates people with diabetes need to be vigilant about. It's the fat too.

A new study from the Joslin Clinic in Boston found that patients with type 1 diabetes required more insulin coverage for a higher-fat meal compared to a lower-fat meal. The meals were prepared in the Clinic's kitchen and had identical carbohydrate and protein, but different fat content - 60 grams vs. 10 grams. The carbohydrates in the meals had similar glycemic indexes.

Dietary Fat Acutely Increases Glucose Concentrations and Insulin Requirements in Patients With Type 1 Diabetes, Diabetes Care, April 2013

It was a small study of crossover design, meaning each participant consumed both the high-fat meal and the low-fat meal.

"RESULTS Seven patients with type 1 diabetes (age, 55 ± 12 years; A1C 7.2 ± 0.8%) successfully completed the protocol. [The high-fat] dinner required more insulin than [the low-fat] dinner (12.6 ± 1.9 units vs. 9.0 ± 1.3 units; P = 0.01) and, despite the additional insulin, caused more hyperglycemia.

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."

Joslin accompanied their study with this short video:

"When people ate a higher fat meal, their blood sugars were higher for longer and required more insulin."

Why does dietary fat lead to higher blood glucose? It is thought that fat contributes to insulin resistance:

"Dietary fat and free fatty acids (FFAs) are known to impair insulin sensitivity and to enhance hepatic glucose production. ... Interventions that lower [free fatty acid] levels in nondiabetic and type 2 diabetic individuals lead to both improved insulin sensitivity and glucose tolerance."

Saturated fat may be more problematic:

"Studies in nondiabetic individuals indicate that saturated fats cause more profound insulin resistance than monounsaturated and polyunsaturated fats. By design, the [high-fat] dinner meal in the current study was predominantly saturated fat."

And:

"Pizza is widely recognized to cause marked late postprandial hyperglycemia in patients with type 1 diabetes."

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