title: Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: The KANWU Study.
abstract: OBJECTIVE
  The amount and quality of fat in the diet could be of importance for development of insulin resistance and related metabolic disorders. Our aim was to determine whether a change in dietary fat quality alone could alter insulin action in humans.
  
  
  METHODS
  The KANWU study included 162 healthy subjects chosen at random to receive a controlled, isoenergetic diet for 3 months containing either a high proportion of saturated (SAFA diet) or monounsaturated (MUFA diet) fatty acids. Within each group there was a second assignment at random to supplements with fish oil (3.6 g n-3 fatty acids/d) or placebo.
  
  
  RESULTS
  Insulin sensitivity was significantly impaired on the saturated fatty acid diet (-10%, p = 0.03) but did not change on the monounsaturated fatty acid diet (+2%, NS) (p = 0.05 for difference between diets). Insulin secretion was not affected. The addition of n-3 fatty acids influenced neither insulin sensitivity nor insulin secretion. The favourable effects of substituting a monounsaturated fatty acid diet for a saturated fatty acid diet on insulin sensitivity were only seen at a total fat intake below median (37E%). Here, insulin sensitivity was 12.5% lower and 8.8% higher on the saturated fatty acid diet and monounsaturated fatty acid diet respectively (p = 0.03). Low density lipoprotein cholesterol (LDL) increased on the saturated fatty acid diet (+4.1%, p < 0.01) but decreased on the monounsaturated fatty acid diet (MUFA) (-5.2, p < 0.001), whereas lipoprotein (a) [Lp(a)] increased on a monounsaturated fatty acid diet by 12% (p < 0.001).
  
  
  CONCLUSIONS
  A change of the proportions of dietary fatty acids, decreasing saturated fatty acid and increasing monounsaturated fatty acid, improves insulin sensitivity but has no effect on insulin secretion. A beneficial impact of the fat quality on insulin sensitivity is not seen in individuals with a high fat intake (> 37E%).
authors.affiliation: Unit for Clinical Nutrition Research, Department of Public Health and Caring Sciences/Geriatrics, University of Uppsala, Uppsala, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Vessby
authors.forename: M
authors.initials: M
authors.lastname: Uusitupa
authors.forename: K
authors.initials: K
authors.lastname: Hermansen
authors.forename: G
authors.initials: G
authors.lastname: Riccardi
authors.forename: A A
authors.initials: AA
authors.lastname: Rivellese
authors.forename: L C
authors.initials: LC
authors.lastname: Tapsell
authors.forename: C
authors.initials: C
authors.lastname: Nälsén
authors.forename: L
authors.initials: L
authors.lastname: Berglund
authors.forename: A
authors.initials: A
authors.lastname: Louheranta
authors.forename: B M
authors.initials: BM
authors.lastname: Rasmussen
authors.forename: G D
authors.initials: GD
authors.lastname: Calvert
authors.forename: A
authors.initials: A
authors.lastname: Maffetone
authors.forename: E
authors.initials: E
authors.lastname: Pedersen
authors.forename: I B
authors.initials: IB
authors.lastname: Gustafsson
authors.forename: L H
authors.initials: LH
authors.lastname: Storlien
mesh_terms: D000328:Adult; D000368:Aged; D016632:Apolipoprotein A-I / Q000097:blood; D001055:Apolipoproteins B / Q000097:blood; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D002784:Cholesterol / Q000097:blood; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D004041:Dietary Fats / Q000494:pharmacology*; D004042:Dietary Fats, Unsaturated / Q000494:pharmacology*; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology*; D015525:Fatty Acids, Omega-3 / Q000494:pharmacology; D005260:Female; D005395:Fish Oils / Q000494:pharmacology; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood* / Q000378:metabolism*; D000078790:Insulin Secretion; D017270:Lipoprotein(a) / Q000097:blood; D008297:Male; D008875:Middle Aged; D010743:Phospholipids / Q000097:blood* / Q000737:chemistry; D012016:Reference Values; D014280:Triglycerides / Q000097:blood
chemical_list: D016632:Apolipoprotein A-I; D001055:Apolipoproteins B; D001786:Blood Glucose; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D004041:Dietary Fats; D004042:Dietary Fats, Unsaturated; D005229:Fatty Acids, Monounsaturated; D015525:Fatty Acids, Omega-3; D005395:Fish Oils; D007328:Insulin; D017270:Lipoprotein(a); D010743:Phospholipids; D014280:Triglycerides; D002784:Cholesterol