Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: The KANWU Study

Diabetologia. 2001 Mar;44(3):312-9. doi: 10.1007/s001250051620.


Aims/hypothesis: 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/interpretation: 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%).

Publication types

  • Clinical Trial
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Apolipoprotein A-I / blood
  • Apolipoproteins B / blood
  • Blood Glucose / drug effects
  • Blood Glucose / metabolism*
  • Cholesterol / blood
  • Cholesterol, HDL / blood
  • Cholesterol, LDL / blood
  • Dietary Fats / pharmacology*
  • Dietary Fats, Unsaturated / pharmacology*
  • Fatty Acids, Monounsaturated / pharmacology*
  • Fatty Acids, Omega-3 / pharmacology
  • Female
  • Fish Oils / pharmacology
  • Glucose Tolerance Test
  • Humans
  • Insulin / blood*
  • Insulin / metabolism*
  • Insulin Secretion
  • Lipoprotein(a) / blood
  • Male
  • Middle Aged
  • Phospholipids / blood*
  • Phospholipids / chemistry
  • Reference Values
  • Triglycerides / blood


  • Apolipoprotein A-I
  • Apolipoproteins B
  • Blood Glucose
  • Cholesterol, HDL
  • Cholesterol, LDL
  • Dietary Fats
  • Dietary Fats, Unsaturated
  • Fatty Acids, Monounsaturated
  • Fatty Acids, Omega-3
  • Fish Oils
  • Insulin
  • Lipoprotein(a)
  • Phospholipids
  • Triglycerides
  • Cholesterol