title: Dietary macronutrient composition affects β cell responsiveness but not insulin sensitivity.
abstract: BACKGROUND
  Altering dietary carbohydrate or fat content may have chronic effects on insulin secretion and sensitivity, which may vary with individual metabolic phenotype.
  
  
  OBJECTIVE
  The objective was to evaluate the contribution of tightly controlled diets differing in carbohydrate and fat content for 8 wk to insulin sensitivity and β cell responsiveness and whether effects of diet would vary with race, free-living diet, or insulin response.
  
  
  METHODS
  Healthy overweight men and women (36 European Americans, 33 African Americans) were provided with food for 8 wk and received either a eucaloric standard diet (55% carbohydrate, 27% fat) or a eucaloric reduced-carbohydrate (RedCHO)/higher-fat diet (43% carbohydrate, 39% fat). Insulin sensitivity and β cell responsiveness were assessed at baseline and 8 wk by using a liquid meal tolerance test.
  
  
  RESULTS
  Insulin sensitivity did not change with diet (P = 0.1601). Static β cell response to glucose (ФS) was 28.5% lower after the RedCHO/higher-fat diet. Subgroup analyses indicated that lower ФS with the RedCHO/higher-fat diet occurred primarily among African Americans. A significant inverse association was observed for change in glucose area under the curve compared with change in ФS.
  
  
  CONCLUSIONS
  Consumption of a eucaloric 43% carbohydrate/39% fat diet for 8 wk resulted in down-regulation of β cell responsiveness, which was influenced by baseline phenotypic characteristics. Further study is needed to probe the potential cause-and-effect relation between change in ФS and change in glucose tolerance. This trial is registered at clinicaltrials.gov as NCT00726908.
authors: Department of Nutrition Sciences at the University of Alabama at Birmingham, Birmingham, AL 35294-3360, USA.
authors: Laura Lee
authors: LL
authors: Goree
authors: Paula
authors: P
authors: Chandler-Laney
authors: Amy C
authors: AC
authors: Ellis
authors: Krista
authors: K
authors: Casazza
authors: Wesley M
authors: WM
authors: Granger
authors: Barbara A
authors: BA
authors: Gower
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