As discussed by Robergs and Roberts [22], amino acid catabolism during exercise is important for three reasons: 1) for free energy during exercise to fuel muscle contraction; 2) to increase concentrations of citric acid cycle intermediates and therefore support carbohydrate and lipid catabolism; and 3) to serve as gluconeogenic precursors. (jissn.biomedcentral.com)
In skeletal muscle, fat certainly does not burn in a carbohydrate flame, as skeletal muscle does not have sufficient quantities of the enzymes to convert glycolytic intermediates into molecules that can be transported into the mitochondria to supplement citric acid cycle intermediates. (jissn.biomedcentral.com)