Ev. Lambert et al., High-fat diet versus habitual diet prior to carbohydrate loading: Effects on exercise metabolism and cycling performance, INT J SP N, 11(2), 2001, pp. 209-225
Citations number
38
Categorie Soggetti
Ortopedics, Rehabilitation & Sport Medicine
Journal title
INTERNATIONAL JOURNAL OF SPORT NUTRITION AND EXERCISE METABOLISM
We examined the effects of a high-fat diet (HFD-CHO) versus a habitual diet
, prior to carbohydrate (CHO)-loading on fuel metabolism and cycling time-t
rial (Tf) performance. Five endurance-trained cyclists participated in two
14-day randomized cross-over trials during which subjects consumed either a
HFD (> 65% MJ from fat) or their habitual diet (CTL) (30 +/- 5% MJ from fa
t) for 10 days, before ingesting a high-CHO diet (CHO-loading, CHO > 70% MJ
) for 3 days. Trials consisted of a 150-min cycle at 70% of peak oxygen upt
ake ((V) over dotO(2peak)), followed immediately by a 20-km TT. One hour be
fore each trial, cyclists ingested 400 mi of a 3.44% medium-chain triacylgl
ycerol (MCT) solution, and during the trial, ingested 600 ml/hour of a 10%
14C-glucose + 3.44% MCT solution. The dietary treatments did not alter the
subjects' weight, body fat, or Lipid profile. There were also no changes in
circulating glucose, lactate, free fatty acid (FFA), and P-hydroxybutyrate
concentrations during exercise. However, mean serum glycerol concentration
s were significantly higher (p < .01)ill the HFD-CHO trial. The HFD-CHO die
t increased total fat oxidation and reduced total CHO oxidation but did not
alter plasma glucose oxidation during exercise. By contrast, the estimated
rates of muscle glycogen and lactate oxidation were lower after the HFD-CH
O diet. The HFD-CHO treatment was also associated with improved TT times (2
9.5 +/- 2.9 min vs. 30.9 +/- 3.4 min for HFD-CHO and CTL-CHO, p < .05). Hig
h-fat feeding for 10 days prior to CHO-loading was associated with an incre
ased reliance on fat, a decreased reliance on muscle glycogen, and improved
time trial performance after prolonged exercise.