This notion of being a "sugar burner" vs. a "fat burner" -- with the latter being touted as preferable based on nothing I've seen in the scientific literature -- is getting really out of hand. This is not a new idea, but it certainly seems to be being pushed more lately, particularly in the area of athletic performance. There were a smattering of posts about the diets of Olympians about the net and I just have to shake my head at the one that goes something like "just imagine how much better fill in the blank would do if (s)he didn't eat grains" or "ate LCHF" or "went paleo". C'mon already ... Michael Phelps is a prime offender of all laws and gods nutritional, but will someone please remind me how many medals he's earned and records he's held/broken in his career? Gawd forbid any of these elite athletes set a bad example by having their face put on a box of Wheaties! I dunno ... it all seems so silly when Phelps sports one of the leanest torsos on the planet burning sugar. But I digress ...
But with ketomania in full-blown fad form, there's a new twist on the fat burning meme which is to confuse fat burning with ketone burning. It is not. Yes, ketones are produced mostly from the breakdown of fatty acids (they are also produced from some amino acids), so you "burn fat" in your liver to produce them. If you are in caloric deficit, the source of the fatty acids will be body fat. However, if you're fueling the other cells of your body with ketones, this is not the same as the mitochondria in those cells "burning fat".
Below is a schematic of a brain cell mitochondria and the metabolic pathways showing where ketones feed into Krebs (aka the TCA), from: D-β-Hydroxybutyrate protects neurons in models of Alzheimer's and Parkinson's disease (thus it shows the points of issue for these two diseases)
