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Carbohydrate metabolism during exercise in females : effect of reduced fat availability

journal contribution
posted on 2001-04-01, 00:00 authored by Kirsten HowlettKirsten Howlett, L Spriet, Mark Hargreaves
This study examined the effect of reduced plasma free fatty acid (FFA) availability on carbohydrate metabolism during exercise. Six untrained women cycled for 60 minutes at approximately 58% of maximum oxygen uptake after ingestion of a placebo (CON) or nicotinic acid (NA), 30 minutes before exercise (7.4 ± 0.5 mg·kg−1 body weight), and at 0 minutes (3.7 ± 0.3 mg·kg−1) and 30 minutes (3.7 ± 0.3 mg·kg−1) of exercise. Glucose kinetics were measured using a primed, continuous infusion of [6,6-2H] glucose. Plasma FFA (CON, 0.86 ± 0.12; NA, 0.21 ± 0.11 mmol·L−1 at 60 minutes, P < .05) and glycerol (CON, 0.34 ± 0.05; NA, 0.10 ± 0.04 mmol·L−1 at 60 minutes, P < .05) were suppressed throughout exercise. Mean respiratory exchange ratio (RER) during exercise was higher (P < .05) in NA (0.89 ± 0.02) than CON (0.83 ± 0.02). Plasma glucose and glucose production were similar between trials. Total glucose uptake during exercise was greater (P < .05) in NA (1,876 ± 161 μmol·kg−1) than in CON (1,525 ± 107 μmol·kg−1). Total fat oxidation was reduced (P < .05) by approximately 32% during exercise in NA. Total carbohydrate oxidized was approximately 42% greater (P < .05) in NA (412 ± 40 mmol) than CON (290 ± 37 mmol), of which, approximately 16% (20 ± 10 mmol) could be attributed to glucose. Plasma insulin and glucagon were similar between trials. Catecholamines were higher (P < .05) during exercise in NA. In summary, during prolonged moderate exercise in untrained women, reduced FFA availability results in a compensatory increase in carbohydrate oxidation, which appears to be due predominantly to an increase in glycogen utilization, although there was a small, but significant, increase in whole body glucose uptake.

History

Journal

Metabolism, clinical and experimental

Volume

50

Issue

4

Pagination

481 - 487

Publisher

WB Saunders Co.

Location

Duluth, Minn.

ISSN

0026-0495

eISSN

1532-8600

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2001, W.B. Saunders Company