Dietary macronutrient composition affects β cell responsiveness but not insulin sensitivity

Area of Science:

• Metabolic Health
• Nutritional Science
• Endocrinology

Background:

• Dietary carbohydrate and fat content can influence long-term insulin secretion and sensitivity.
• Individual metabolic phenotypes may affect responses to dietary changes.

Purpose of the Study:

• To assess how controlled diets, varying in carbohydrate and fat, affect insulin sensitivity and beta cell responsiveness over 8 weeks.
• To determine if diet effects differ by race, free-living diet, or baseline insulin response.

Main Methods:

• Healthy overweight adults (36 European Americans, 33 African Americans) consumed either a standard diet (55% carb, 27% fat) or a reduced-carbohydrate/higher-fat diet (43% carb, 39% fat) for 8 weeks.
• Insulin sensitivity and beta cell responsiveness were measured using a liquid meal tolerance test at baseline and after 8 weeks.

Main Results:

• No significant changes in insulin sensitivity were observed between the diets.
• The reduced-carbohydrate/higher-fat diet led to a 28.5% decrease in static beta cell response to glucose (ФS).
• This reduction in ФS was predominantly seen in African American participants and was inversely associated with changes in glucose area under the curve.

Conclusions:

• An 8-week eucaloric diet with 43% carbohydrate and 39% fat down-regulated beta cell responsiveness.
• Dietary effects on beta cell responsiveness were influenced by baseline phenotypic characteristics.
• Further research is needed to clarify the relationship between changes in beta cell responsiveness and glucose tolerance.