Fasted Cardio does NOT Increase Fat oxidation

[Venom]

The study we have all been waiting for. Check it out!



1: J Appl Physiol. 2008 Apr;104(4):1045-55. Epub 2008 Feb 14.
Effect of training in the fasted state on metabolic responses during exercise with carbohydrate intake.

De Bock K, Derave W, Eijnde BO, Hesselink MK, Koninckx E, Rose AJ, Schrauwen P, Bonen A, Richter EA, Hespel P.
Research Center for Exercise and Health, F.A.B.E.R. - K.U.Leuven, Tervuursevest 101, B-3001 Leuven Heverlee, Belgium.
Skeletal muscle gene response to exercise depends on nutritional status during and after exercise, but it is unknown whether muscle adaptations to endurance training are affected by nutritional status during training sessions. Therefore, this study investigated the effect of an endurance training program (6 wk, 3 day/wk, 1-2 h, 75% of peak Vo(2)) in moderately active males. They trained in the fasted (F; n = 10) or carbohydrate-fed state (CHO; n = 10) while receiving a standardized diet [65 percent of total energy intake (En) from carbohydrates, 20%En fat, 15%En protein]. Before and after the training period, substrate use during a 2-h exercise bout was determined. During these experimental sessions, all subjects were in a fed condition and received extra carbohydrates (1 g.kg body wt(-1) .h(-1)). Peak Vo(2) (+7%), succinate dehydrogenase activity, GLUT4, and hexokinase II content were similarly increased between F and CHO. Fatty acid binding protein (FABPm) content increased significantly in F (P = 0.007). Intramyocellular triglyceride content (IMCL) remained unchanged in both groups. After training, pre-exercise glycogen content was higher in CHO (545 +/- 19 mmol/kg dry wt; P = 0.02), but not in F (434 +/- 32 mmol/kg dry wt; P = 0.23). For a given initial glycogen content, F blunted exercise-induced glycogen breakdown when compared with CHO (P = 0.04). Neither IMCL breakdown (P = 0.23) nor fat oxidation rates during exercise were altered by training. Thus short-term training elicits similar adaptations in peak Vo(2) whether carried out in the fasted or carbohydrate-fed state. Although there was a decrease in exercise-induced glycogen breakdown and an increase in proteins involved in fat handling after fasting training, fat oxidation during exercise with carbohydrate intake was not changed.

[Builder15]

Did you read the entire study because you cannot draw that conclusion based on just the abstract. I'll see if i can get a copy of the study and read it cause it sure is interesting.

[Venom]

Yeah I have been studying it. I do see some issues actually. I am really tired right now so correct me if you get a chance to read it. But from what I see they were mostly concerned with if there were any beneficial adaptations to training in the fasted state. So they had them train fasted or w/ carbs in morning for 6 weeks, 3 times weekly. BUT then they transfered both to a carbohydrate meal at the end and measured fat oxidation under those conditions (optimal conditions for endurnance performance) and found no differences in fat oxidation. So if I am right they were not measuring acute fat oxidation in fasted state, but rather in the carbohdrate fed state 6 weeks after doing it in the fasted or carb fed state, to see if fat oxidation was greater, even when fed carbs. I probably lost some of u there but Im exhuasted. Could have read this wrong.

Another issue I have is that they gave them very high carb diets (65%) and in those conditions it may not make a difference what your pre-workout carb meal is.

[Commander]

Still sounds like good news to me, even with some slight flaws.

[Venom]

Yeah, I agree. It does tell us something about the long term effects. There was no difference in body comp either; but they were on a maintainence diet.