Effect of high-fat and high-carbohydrate diets on pulmonary O sub( 2) uptake kinetics during the transition to moderate-intensity exercise

• Published in: Journal of applied physiology (1985) Vol. 117; no. 11; p. 1371
• Main Authors: Raper, J A, Love, L K, Paterson, D H, Peters, S J, Heigenhauser, G J F, Kowalchuk, J M
• Format: Journal Article
• Language: English
• Published: 01.12.2014
• ISSN: 8750-7587

Mitochondrial pyruvate dehydrogenase (PDH) regulates the delivery of carbohydrate-derived substrate to the mitochondrial tricarboxylic acid cycle and electron transport chain. PDH activity at rest and its activation during exercise is attenuated following high-fat (HFAT) compared with high-carbohydrate (HCHO) diets. Given the reliance on carbohydrate-derived substrate early in transitions to exercise, this study examined the effects of HFAT and HCHO on phase II pulmonary O2 uptake (V...) kinetics during transitions into the moderate-intensity (MOD) exercise domain. Eight active adult men underwent dietary manipulations consisting of 6 days of HFAT (73% fat, 22% protein, 5% carbohydrate) followed immediately by 6 days of HCHO (10% fat, 10% protein, 80% carbohydrate); each dietary phase was preceded by a glycogen depletion protocol. Participants performed three MOD transitions from a 20 W cycling baseline to work rate equivalent to 80% of estimated lactate threshold on days 5 and 6 of each diet. Steady-state V... was greater (P < 0.05), and respiratory exchange ratio and carbohydrate oxidation rates were lower (P < 0.05) during HFAT. The phase II V... time constant (...) [HFAT 40 plus or minus 16, HCHO 32 plus or minus 19 s (mean plus or minus SD)] and V... gain (HFAT 10.3 plus or minus 0.8, HCHO 9.4 plus or minus 0.7 ml-min...-W...) were greater (P < 0.05) in HFAT. The overall adjustment (effective time constant) of muscle deoxygenation (...[HHb]) was not different between diets (HFAT 24 plus or minus 4 s, HCHO 23 plus or minus 4 s), which coupled with a slower ..., indicates a slowed microvascular blood flow response. These results suggest that the slower V... kinetics associated with HFAT are consistent with inhibition and slower activation of PDH, a lower rate of pyruvate production, and/or attenuated microvascular blood flow and O2 delivery. (ProQuest: ... denotes formulae/symbols omitted.)