Increase in fat oxidation on a high-fat diet is accompanied by an increase in triglyceride-derived fatty acid oxidation.
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 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-13C]palmitate (0.00806 micromol x min(-1) x kg(-1)) was started and continued for 2 h at rest followed by 1 h of exercise at 50% of maximal power output (Wmax). Whole-body fat oxidation was measured using indirect calorimetry, and plasma-derived fatty acid oxidation was evaluated by measuring breath 13CO2 enrichment and corrected with the acetate recovery factor. Twenty-four-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. Triglyceride-derived fatty acid oxidation tended to be higher after 7 days of high-fat diet at rest (P < 0.07). This difference was significant during exercise (P < 0.05). In conclusion, the results from this study suggest that triglyceride-derived 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.
Schrauwen
P
P
Department of Human Biology, Maastricht University, The Netherlands. p.schrauwen@hb.unimaas.nl
Wagenmakers
A J
AJ
van Marken Lichtenbelt
W D
WD
Saris
W H
WH
Westerterp
K R
KR
D000328:Adult; D002153:Calorimetry, Indirect; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage*; D015444:Exercise / Q000502:physiology; D005227:Fatty Acids / Q000097:blood*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005502:Food; D006003:Glycogen / Q000097:blood; D006801:Humans; D007223:Infant; D015227:Lipid Peroxidation; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D014280:Triglycerides / Q000097:blood*
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D014280:Triglycerides; D006003:Glycogen