Fats are completely digested down to free fatty acids, then reconstructed again as triglycerides for storage. Your body does not store olive oil fats or beef fats, it stores human-specific fats. This is not a zero energy process, but neither is the breakdown of proteins to amino acids or the various carbohydrates to sugars. The fat pathways are much less efficient, but probably not to the extent that the metabolic effect is significant.
What is significant is that fat and protein take longer to break down and get to the cells, so they don’t cause systemic spikes of macronutrients; this allows your body to apportion nutrients as it needs, rather than as a response to abnormal levels. This is the primary benefit of lowered carb diets, that your body doesn’t have to spike insulin because it sees a sugar level it doesn’t like. Your body also doesn’t have to store fat- if you don’t believe me, drink a cup of olive oil and report back; too much sugar that your body can’t absorb will have the same effect, like what happens with the lactose intolerant.
I think that this is the justification for recommendations to eat protein and carbs or protein and fats, but not all three together in significant quantities or carbs and fats together, because of the storage effects. I think that more fat ingested as part of a low carb diet will end up utilized as energy before being stored.[/quote]
I’m sure you don’t actually mean this, but the order in which you’ve written your information at least IMPLIES that low insulin has something to do with more fat being burned. And I’m almost positive that has nothing to do with it.
A low carb diet generally means lower glycogen stores, and the lower your glycogen stores, the greater proportion of fats are burned for energy. The higher the glycogen stores, the more of the energy required for physical activity will come from glycogen.
Yes, I’m aware I wrote “low insulin” and then “low carb” in the next paragraph. That’s what I mean: you started talking about insulin and then jump to low carb (nothing wrong with the jump) but the flow of information implies the association I’m talking about.
Of course, it depends on what type activity you’re doing, but again I think you forgot to mention that more fat being burned on a low carb diet is due to lower average glycogen stores, not less insulin spikes. At least, that’s what your text implied (or what I felt it implied).