Fatty acid composition in serum lipids and adipose tissue in severe obesity before and after six weeks of weight loss.

Fatty acid composition was studied in 25 grossly obese patients (mean weight 116 +/- 21 (s.d.) kg) before and after 6 weeks of treatment with a combined program consisting of diet, behavioral modification and light exercise. Data were compared with results from nonobese controls. In obese patients the most marked differences were reduced relative contents of linoleic acid in serum triglycerides (P less than 0.001), cholesterol esters (P less than 0.05) and phospholipids (P less than 0.001). Linolenic acid was reduced in serum triglycerides (P less than 0.001) and in cholesterol esters (P less than 0.01). There were reciprocal increases in palmitic and palmitoleic acid (P less than 0.05) in these two serum lipid fractions. In adipose tissue of obese patients only minor differences were found in palmitoleic acid, which was increased, and in the saturated fatty acids with 14, 16 and 18 carbon atoms which were decreased. Weight loss (600 kcal/day for 6 weeks, P/S ratio about 0.5) did not affect adipose tissue fatty acid composition, but resulted in reductions of linoleic acid content in cholesterol esters and phospholipids, with reciprocal increases of palmitic and arachidonic acid in these fractions. Our results suggest that obese patients have low essential fatty acids content in their circulating plasma lipids already in a weight stable phase. Therefore it may be argued that in the development of long-term dietary restriction programs attention should be paid to the quality of the dietary fat.