Abstract
We previously reported that a eucaloric, low fat, liquid formula diet enriched in simple carbohydrate markedly increased the synthesis of fatty acids in lean volunteers. To examine the diet sensitivity of obese subjects, 7 obese and 12 lean volunteers were given two eucaloric low fat solid food diets 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 sugar to starch 60:40). The fatty acid compositions of both diets were matched to the composition of each subject's adipose tissue and fatty acid synthesis measured by the method of linoleate dilution in plasma VLDL triglyceride. 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%) subjects, 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 after infusion of [13C]acetate. On the 10% fat diet, plasma triglycerides (fasting and 24 h) were increased and correlated with fatty acid synthesis. Triglycerides were higher when fatty acid synthesis was constantly elevated rather than having diurnal variation. Thus, eucaloric, solid food diets which are very low in fat and high in simple sugars markedly stimulate fatty acid synthesis from carbohydrate, and plasma triglycerides increase in proportion to the amount of fatty acid synthesis. However, this dietary effect is not related to body mass index, insulin, or glucagon levels.—Hudgins, L. C., M. K. Hellerstein, C. E. Seidman, R. A. Neese, J. D. Tremaroli, and J. Hirsch. Relationship between carbohydrate-induced hypertriglyceridemia and fatty acid synthesis in lean and obese subjects. J. Lipid Res. 2000. 41: 595–604.
Highlights
We previously reported that a eucaloric, low fat, liquid formula diet enriched in simple carbohydrate markedly increased the synthesis of fatty acids in lean volunteers
We reported a marked increase in newly synthesized palmitate (16:0) and decrease in the essential fatty acid, linoleate (18:2), in plasma triglyceride (TG) and very low density lipoprotein (VLDL) TG after the equicaloric substitution of dietary simple carbohydrate for fat in lean volunteers fed liquid formula diets [4]
The fasting fatty acid compositions in VLDL TG were constant the last 4 days of the 14-day diets, indicating that maximal stimulation or suppression of fasting fatty acid synthesis had occurred by day 10, as was observed in our previous study of 25 days [4]
Summary
We previously reported that a eucaloric, low fat, liquid formula diet enriched in simple carbohydrate markedly increased the synthesis of fatty acids in lean volunteers. Eucaloric, solid food diets which are very low in fat and high in simple sugars markedly stimulate fatty acid synthesis from carbohydrate, and plasma triglycerides increase in proportion to the amount of fatty acid synthesis This dietary effect is not related to body mass index, insulin, or glucagon levels.—Hudgins, L. The same lipid profile is often associated with obesity and, in particular, an excess of visceral fat in the abdomen, as well as increased fasting and postprandial blood insulin levels and decreased tissue sensitivity to insulin [16, 18] It is unknown whether obese subjects who commonly have insulin resistance, high insulin levels, and low glucagon levels are more sensitive to the de novo lipogenic effects of low fat, high carbohydrate diets which may raise insulin levels [19]. Using mass isotopomer distribution analysis (MIDA) to measure fatty acid synthesis in vivo, fatty acid synthesis was positively related to body mass index in a small number of lean and severely obese, hyperinsulinemic subjects after an uncontrolled ad libitum diet [25]
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