When it comes to cardio and fat loss, it really is a case of the blind leading the blind. Most trainees have been made believe that cardio burns only fat and weight lifting builds muscle, hence you must combine the two to create a perfect physique.
Aside from the fact, that weight lifting is very similar in its results for fat loss than cardio when viewed over a 24 hours period, it also offers the potential of reshaping the body which cardio doesn't.
Still ,cardio can be used as an additional energy expenditure to lose more weight as long as a proper weight lifting protcol is being followed.
For a long time, it was very common to get on the stepper/treadmill first thing in the morning to "burn only fat". The reasoning is that your body doesnt have any nutrients to burn so it will use fat for fuel. Sounds logical but doesnt work that way.
When looking at fat loss, one has to look at a 24 hour time span not just the actual exercise time. Studies have shown that a pre workout carb feeding did not decrease fat oxidation in any significant manner. But it did two very important things: it allowed the athlete to train with greater overall intensity, meaning more overall energy was used and it acted as a protection for the muscle and prevent catabolism.
If you are on a very low-carb diet and simply do not have any room for carbs, simply consume some whey protein before the workout for a similar effect.
Till next time
Maik
Sources
Melanson EL, et al. Resistance and aerobic exercise have similar effects on 24-h nutrient oxidation.. Med Sci Sports Exerc. 2002 Nov;34(11):1793-800.
Ahlborg, G., and P. Felig. Influence of glucose ingestion on fuel-hormone response during prolonged exercise. J. Appl. Physiol. 1976;41:683-688.
Coyle, et al.. Carbohydrates during prolonged strenuous exercise can delay fatigue. J. Appl. Physiol. 59: 429-433, 1983.
Horowitz JF, et al. Substrate metabolism when subjects are fed carbohydrate during exercise. Am J Physiol. 1999 May;276(5 Pt 1):E828-35.