title: Diets high in protein or saturated fat do not affect insulin sensitivity or plasma concentrations of lipids and lipoproteins in overweight and obese adults.
abstract: BACKGROUND
  Previous human studies reported inconsistent effects of dietary protein and branched-chain amino acids (BCAAs) on insulin action and glucose metabolism. Similarly, it is unclear whether saturated fat (SF) intake influences these metabolic variables.
  
  
  OBJECTIVE
  The objective of this study was to test the effects of high [30% of energy (%E)] vs. moderate (20%E) intakes of protein (primarily whey) on insulin action and lipid and lipoprotein concentrations in the context of both high (15%E) and low (7%E) SF diets.
  
  
  METHODS
  The study was conducted as a randomized controlled trial in 158 overweight and obese men and women. After a 4-wk baseline diet [55%E carbohydrate, 15%E protein, 30%E fat (7%E SF)], participants were randomly assigned to 4 wk of either the baseline diet or 1 of 4 test diets containing 35%E carbohydrate and either 20%E or 30%E protein and either 7%E or 15%E SF. Frequently sampled i.v. glucose tolerance tests were administered after each dietary period.
  
  
  RESULTS
  Other than significantly higher fasting glucose concentrations for high vs. moderate protein intakes with a low-fat diet (difference ± SE: 0.47 ± 0.14 mmol/L; P = 0.001), there were no significant effects of dietary protein or SF on glucose metabolism, plasma insulin, or concentrations of lipids and lipoproteins. Changes in plasma BCAAs across all diets were negatively correlated with changes in the metabolic clearance rate of insulin (ρ = -0.18, P = 0.03) and positively correlated with changes in the acute insulin response to glucose (ρ = 0.15, P = 0.05).
  
  
  CONCLUSIONS
  These findings suggest that short-term intake of BCAAs can influence insulin dynamics. However, in this group of overweight and obese individuals, neither high protein nor SF intake affected insulin sensitivity or plasma concentrations of lipids and lipoproteins. This trial was registered at clinicaltrials.gov as NCT00508937.
authors.affiliation: Children's Hospital Oakland Research Institute, Oakland, CA.
authors.forename: Sally
authors.initials: S
authors.lastname: Chiu
authors.affiliation: Lawrence Berkeley National Laboratory, Berkeley, CA.
authors.forename: Paul T
authors.initials: PT
authors.lastname: Williams
authors.affiliation: Children's Hospital Oakland Research Institute, Oakland, CA.
authors.forename: Taylor
authors.initials: T
authors.lastname: Dawson
authors.affiliation: Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA; and.
authors.forename: Richard N
authors.initials: RN
authors.lastname: Bergman
authors.affiliation: Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA; and.
authors.forename: Darko
authors.initials: D
authors.lastname: Stefanovski
authors.affiliation: Lipomics (a division of Metabolon), West Sacramento, CA.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Watkins
authors.affiliation: Children's Hospital Oakland Research Institute, Oakland, CA rkrauss@chori.org.
authors.forename: Ronald M
authors.initials: RM
authors.lastname: Krauss
mesh_terms: D000328:Adult; D004041:Dietary Fats / Q000494:pharmacology*; D004044:Dietary Proteins / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008055:Lipids / Q000097:blood*; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D008875:Middle Aged; D050177:Overweight / Q000097:blood* / Q000378:metabolism
chemical_list: D004041:Dietary Fats; D004044:Dietary Proteins; D008055:Lipids; D008074:Lipoproteins