In keeping up with the "Stuff I Don't Quite Understand (TM)" series, here's another concept that I still have yet to wrap my head around.
The concept of "fat oxidation" is often to as being a prominent marker of fat loss. Lyle McDonald, for example, has his UD2 diet built entirely around the concept of increasing fat oxidation as much as possible in the "catabolic" phase of the week. He has you start off with a "depletion" workout to burn up glycogen stores as much as possible. He then says that by doing so, whole-body fat oxidation increases - so he has the depletion workout basically set up as a sort of "trick" to get you to burn more fat.
My question: what does this exactly mean? Of course whole-body fat oxidation is going to increase, but why would that make a difference by the end of the week when you recarb? Hasn't all of the data showing that keto diets aren't superior to non-keto diets kind of put this notion to rest? Or the data showing that the "fat burning" cardio zone is a myth?
Is "an increase in fat oxidation" synonymous here with "upregulation of energy expenditure?" Or is something else going on?
My thinking is that perhaps it has something to do with causing glycogen supercompensation to occur on the refeed, but still, why does the depletion workout matter? So let's say you just do a normal workout and end up 1/2 depleted. So whole-body fat oxidation doesn't occur, but glycogen stores slowly dissipate by themselves. Then the next workout you end up depleting the other half. So you'd still end up "dry" when the carbup came around, and glycogen supercompensation would still occur.
So would this not be a better approach, since you'd probably be able to perform better in a non-depleted state? But there seems to be something magical about "increased whole-body fat oxidation" that I'm not getting here.
A cluster**** of questions indeed. Anyone know?
Thread: "Fat oxidation" vs "fat loss"