Relationship between carbohydrate-induced hypertriglyceridemia and fatty acid synthesis in lean and obese subjects

We previously reported that a eucaloric, low fat, liquid formula diet enric hed in simple carbohydrate markedly increased the synthesis of fatty acids in lean volunteers. To examine the diet sensitivity of obese subjects, 7 ob ese and 12 lean volunteers were given two eucaloric low fat solid food diet s enriched in simple sugars for 2 weeks each in a random-order, cross-over design (10% fat, 75% carbohydrate vs. 30% fat, 55% carbohydrate, ratio of s ugar to starch 60:40). The fatty acid compositions of both diets were match ed to the composition of each subject's adipose tissue and fatty acid synth esis measured by the method of linoleate dilution in plasma VLDL triglyceri de. In all subjects, the maximum % de novo synthesized fatty acids in VLDL triglyceride 3-9 h after the last meal was higher on the 10% versus the 30% fat diet. There was no significant difference between the dietary effects on lean (43 +/- 13 vs. 12 +/- 13%) and obese (37 +/- 15 vs. 6 +/- 6%) subje cts, despite 2-fold elevated levels of insulin and reduced glucagon levels in the obese. Similar results were obtained for de novo palmitate synthesis -in VLDL triglyceride measured by mass isotopomer distribution analysis aft er infusion of C-[13]acetate. On the 10% fat diet, plasma triglycerides (fa sting and 24 h) were increased and correlated with fatty acid synthesis. Tr iglycerides were higher when fatty acid synthesis was constantly elevated r ather than having diurnal variation. Thus, eucaloric, solid food diets whic h are very low in fat and high in simple sugars markedly stimulate fatty ac id synthesis from carbohydrate, and plasma triglycerides increase in propor tion to the amount of fatty acid synthesis. However, this dietary effect is not related to body mass index, insulin, or glucagon levels.