F33d Free Communication/Slide Lipid Metabolism
This study determined if the elevated fat oxidation during exercise caused by a low carbohydrate û high fat diet requires β adrenergic stimulation.
Six endurance trained cyclists exercised at 50%VO2peak for 1 hour after a 2 day low-carbohydrate-high fat diet (LC CON) or an isocaloric high-carbohydrate-low fat diet (HC CON). Six additional cyclists consumed both diets and ingested 80 mg of propanolol (β B) 2 hours before exercise to block β adrenergic receptors (HC β B and LC β B).
In the CON condition, the LC CON diet elevated fat oxidation during exercise by 13 ± 2 umol/kg/min vs. HC CON (32 ± 2 vs 19 ± 2 umol FA/kg/min, p < 0.05). Although β B lowered fat oxidation below CON after both diets, fat oxidation was still elevated after LC β B vs. HC β B (19 ± 1 vs 10 ± 1, p < 0.05). In both CON and β B trials, plasma FFA concentrations were not different after HC vs. LC. Furthermore, in both CON and β B trials, indices of whole body lipolysis, Ra glycerol and glycerol concentrations were increased by LC vs. HC diet (p < 0.05).
These data suggest that the elevated fat oxidation and lipolysis during exercise caused by a low-carbohydrate-high fat diet does not require β adrenergic stimulation In addition, because the increased fat oxidation and lipolysis do not appear to depend on elevated plasma FFA concentrations, this suggests that a low-carbohydrateûhigh fat diet increases muscle triglyceride utilization even with reduced β adrenergic stimulation. Supported by ACSM Reebok Student Award and Texas ACSM Student Research Grant