Insulin resistance is characterized by specific changes of the composition of fatty acids in the serum lipids and in the skeletal muscle membranes. Impaired insulin sensitivity is associated with high proportions of palmitic (16:0) acid and low levels of linoleic (18:2 n‐6) acid in serum. In addition, there are apparent changes of the fatty acid desaturase activities, suggesting an increased activity of the Δ9 and Δ6 desaturases and a decreased activity of the Δ5 desaturase. The activity of the fatty acid desaturases is regulated by long‐chain polyunsaturated fatty acids and insulin and is probably also dependent on the degree of physical activity. A high ratio between arachidonic (20:4 n‐6) and dihomo‐gamma linolenic (20:3 n‐6) acid, as a measure of Δ5 desaturase activity, in the skeletal muscle phospholipids has been related to good insulin sensitivity. Available knowledge seems to indicate that the degree of saturation of the body lipids, and especially the proportion of palmitic acid in the lipid membranes, may be critical for insulin sensitivity. The strong relationships between the Δ5 desaturase activity, a high content of long‐chain polyunsaturated fatty acids in the skeletal muscle, and insulin sensitivity may be due to parallel effects of diet and/or physical activity on the fatty acid composition and on insulin sensitivity.

Summary Recent data indicate that peripheral insulin sensitivity may be influenced by dietary fat quality and skeletal muscle phospholipid fatty acid composition. During a health survey of 70-year-old men insulin sensitivity was measured by the euglycaemic hyperinsulinaemic clamp technique and the fatty acid composition of the serum cholesterol esters was determined (n = 215) by gas liquid chromatography In a subsample the fatty acids of the skeletal muscle phospholipids and triglycerides were determined after fine needle biopsy from m. vastus lateralis (n = 39). The peripheral insulin sensitivity was significantly and negatively correlated to the proportion of palmitic (r = -0.31, p < 0.001), palmitoleic (r = -0.25, p < 0.001) and di-homo-7-1inolenic (r = -0.33, p < 0.001) acids and positively to the content of linoleic (r = 0.28, p < 0.001) acid in the serum cholesterol esters. There was an even stronger negative relationship to the proportion of palmitic acid in the skeletal muscle phospholipds (r = -0.45, p < 0.004). The fatty acid composition was also significantly related to insulin sensitivity in a stepwise multiple regression analysis in the presence of other clinical variables, which were associated with insulin action in univariate analysis. Thus, more than 51% of the variation of the insulin sensitivity was explained by an equation containing body mass index, serum triglyceride concentration and the content of palmitic acid in the skeletal muscle phospholipids. It is concluded that the fatty acid composition in serum and of the phospholipids of skeletal muscle may influence insulin action in elderly men. [Diabetologia (1994[Diabetologia ( ) 37: 1044[Diabetologia ( -1050 Key words Cholsterol esters, fatty acid composition, insulin sensitivity, palmitic acid, phospholipids, skeletal muscle.Recent data indicate that peripheral insulin sensitivity may be influenced by dietary fat quality and by skeletal muscle phospholipid fatty acid composition. A high proportion of n-3 fatty acids in the food to rats fed high fat diets reduces the risk of developing peripheral insulin resistance [1,2]. In humans, a high concentration of long chain polyunsaturated fatty acids in the skeletal muscle phospholipids was associated with an increased insulin sensitivity, suggesting that changes in the fatty acid composition of the cell membranes may modulate the action of insulin [3]. Received: 22 February 1994 and in revised form: 30 May 1994Corresponding author: Dr. B. Vessby, Department of Geriatrics, Uppsala University, PO Box 2151, S-750 02 Uppsala, Sweden The present study was undertaken to investigate the association between the fatty acid composition of serum cholesterol esters and skeletal muscle phospholipids and triglycerides on the one hand and peripheral insulin sensitivity, as measured by the euglycaemic hyperinsulinaemic clamp technique, on the other. The investigation was performed in 70-yearold men as a part of an ongoing health survey. Also, associations between other clinical characteristics and insulin sens...

This study gives no clear support to the hypothesis that a moderately increased intake of dairy products beneficially affects aspects of the metabolic syndrome. The apparently positive effects on waist circumference and sagittal abdominal diameter in subjects with a low calcium intake suggest a possible threshold in relation to effects on body composition.