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-trial (TT) 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 fat) for 10 day, 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 uptake (V̇O2peak), followed immediately by a 20-km TT. One hour before each trial, cyclists ingested 400 ml of a 3.44% medium-chain triacylglycerol (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 β-hydroxybutyrate concentrations during exercise. However, mean serum glycerol concentrations were significantly higher (p < .01) in the HFD-CHO trial. The HFD-CHO diet 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-CHO diet. The HFD-CHO treatment was also associated with improved TT times (29.5 ± 2.9 min vs. 30.9 ± 3.4 min for HFD-CHO and CTL-CHO, p < .05). High-fat feeding for 10 days prior to CHO-loading was associated with an increased reliance on fat, a decreased reliance on muscle glycogen, and improved time trial performance after prolonged exercise.
Estelle V. Lambert, Julia H. Goedecke, Charl van Zyl, Kim Murphy, John A. Hawley, Steven C. Dennis and Timothy D. Noakes
Anissa Cherif, Romain Meeusen, Abdulaziz Farooq, Joong Ryu, Mohamed Amine Fenneni, Zoran Nikolovski, Sittana Elshafie, Karim Chamari and Bart Roelands
To examine the effects of 3 d of intermittent fasting (3d-IF: abstaining from eating/drinking from dawn to sunset) on physical performance and metabolic responses to repeated sprints (RSs).
Twenty-one active males performed an RS test (2 sets: 5 × 5-s maximal sprints with 25 s of recovery between and 3 min of recovery between sets on an instrumented treadmill) in 2 conditions: counterbalanced fed/control session (CS) and fasting session (FS). Biomechanical and biochemical markers were assessed preexercise and postexercise.
Significant main effects of IF were observed for sprints: maximal speed (P = .016), mean speed (P = .015), maximal power (P = .035), mean power (P = .049), vertical stiffness (P = .032), and vertical center-of-mass displacement (P = .047). Sprint speed and vertical stiffness decreased during the 1st (P = .003 and P = .005) and 2nd sprints (P = .046 and P = .048) of set 2, respectively. Postexercise insulin decreased in CS (P = .023) but not in FS (P = .230). Free-fatty-acid levels were higher in FS than in CS at preexercise (P < .001) and at postexercise (P = .009). High-density lipoprotein cholesterol (HDL-C) was higher at postexercise in FS (1.32 ± 0.22 mmol/L) than in CS (1.26 ± 0.21 mmol/L, P = .039). The triglyceride (TG) concentration was decreased in FS (P < .05) compared with CS.
3d-IF impaired speed and power through a decrease in vertical stiffness during the initial runs of the 2nd set of RS. The findings of the current study confirmed the benefits of 3d-IF: improved HDL-C and TG profiles while maintaining total cholesterol and low-density lipoprotein cholesterol levels. Moreover, improving muscle power might be a key factor to retain a higher vertical stiffness and to partly counteract the negative effects of intermittent fasting.
Ulrika Andersson-Hall, Stefan Pettersson, Fredrik Edin, Anders Pedersen, Daniel Malmodin and Klavs Madsen
carbohydrates, mobilization of triglycerides and delivery of free fatty acids (FFA) via the blood stream ( Kiens et al., 2011 ; Spriet, 2011 ; van Loon et al., 2001 ). These metabolites are heavily influenced by activity level and diet. Various hormones, including glucagon, cortisol, growth hormone
Samuel G. Impey, Kelly M. Hammond, Robert Naughton, Carl Langan-Evans, Sam O. Shepherd, Adam P. Sharples, Jessica Cegielski, Kenneth Smith, Stewart Jeromson, David L. Hamilton, Graeme L. Close and James P. Morton
assessments of insulin concentration were limited to pre- and postexercise time points per se. We also acknowledge the limitations associated with making inferences on muscle free fatty acid uptake on snapshot assessments of circulating NEFA per se. Nonetheless, given recent data demonstrating that acute
Sang-Ho Lee, Steven D. Scott, Elizabeth J. Pekas, Jeong-Gi Lee and Song-Young Park
However, it seems more likely that octacosanol stimulates the conversion of lipids into energy, as an animal study reported that octacosanol intake resulted in greater serum free fatty acid levels, greater free fatty acid oxidation, and a decreased serum TG concentration when compared with a CON group. 9
Trent Stellingwerff, James P. Morton and Louise M. Burke
technologies to investigate cellular signaling events over the past decade has expanded insights into the role of nutritional support in promoting adaptations to exercise. It is now known that many substrates, and in particular muscle glycogen and plasma free fatty acids, act not only as fuels for the exercise
Manuel D. Quinones and Peter W.R. Lemon
maltodextrin (peak 2.5 vs. peak 20.3 mIU·ml −1 ) resulting in a more uniform serum glucose response as well as an increase in both serum free fatty acid and glycerol concentrations ( Roberts et al., 2011 ). Also, the RER with HMS appeared to be lower ( p = .07) at both 60 min (0.92 vs. 0.95) and 90 min (0
included in this analysis comprising 254 subjects. Results : Administration of GH significantly increased lean body mass ( P < .01) and decreased fat mass ( P < .01). In addition, GH increased the exercising levels of glycerol ( P = .01) and free fatty acids ( P < .01) but did not alter the
which NAFLD is an emerging metabolic risk in pediatrics is not fully understood, abdominal adiposity, particularly VAT, is considered as a major predictor ( 9 , 19 ). Visceral adipocytes are more metabolically active compared with subcutaneous adipocytes, thereby increasing free fatty acids secretion
Ralph Beneke, Tobias G.J. Weber and Renate M. Leithäuser
10.1111/j.1748-1716.1984.tb07414.x 6237550 23. Kiilerich K , Gudmundsson M , Birk JB , et al . Low muscle glycogen and elevated plasma free fatty acid modify but do not prevent exercise-induced PDH activation in human skeletal muscle . Diabetes . 2010 ; 59 : 26 – 32 . PubMed doi:10