Increase in fat oxidation on a high-fat diet is accompanied by an increase in triglyceride-derived fatty acid oxidation

P. Schrauwen, A. J. Wagenmakers, W. D. van Marken Lichtenbelt, W. H. Saris, K. R. Westerterp
2000 Diabetes  
and Klaas R. We s t e r t e r p The aim of this study is to investigate the mechanism behind the slow increase in fat oxidation on a high-fat diet. Therefore, we determined 24-h substrate oxidation using respiration chambers and the rate of appearance and oxidation of plasma-derived fatty acids in seven healthy nonobese men (age 23 ± 2 years, height 1.85 ± 0.03 m, weight 70.4 ± 2.3 kg, % body fat 13 ± 1). Before testing, they consumed a low-fat diet (30% fat, 55% carbohydrate) at home for 3
more » ... ) at home for 3 days. Measurements were performed after 1 day consumption of either a low-fat diet (LF), a high-fat diet (HF1, 60% fat, 25% carbohydrate), or a high-fat diet preceded by a glycogen-lowering exercise test (HF1+EX), and after 7 days on a high-fat diet (HF7). After an overnight fast, an infusion of [U-1 3 C]palmitate (0.00806 µmol · min -1 · k g -1 ) was started and continued for 2 h at rest followed by 1 h of exercise at 50% of maximal power output (W m a x ) . Whole-body fat oxidation was measured using indirect c a l o r i m e t r y, and plasma-derived fatty acid oxidation was evaluated by measuring breath 1 3 C O 2 e n r i c h m e n t and corrected with the acetate recovery factor. Tw e n t yfour-hour fat oxidation gradually increased on the high-fat diet. Both at rest and during exercise, there was no change in rate of appearance of fatty acids and plasma-derived fatty acid oxidation. Tr i g l y c e r i d ederived fatty acid oxidation tended to be higher after 7 days of high-fat diet at rest (P < 0.07). This diff e r e n c e was significant during exercise (P < 0.05). In conclusion, the results from this study suggest that triglyceridederived fatty acid oxidation (VLDL or intramuscular triglycerides) plays a role in the increase in fat oxidation on a high-fat diet, but plasma-derived fatty acids remain the major source for fat oxidation. D i a b e t e s 4 9 :6 4 0-646, 2000
doi:10.2337/diabetes.49.4.640 pmid:10871203 fatcat:7626s3d6znbfngkrm5yne5u4hu