Dillinger said:
One thing I'm not sure of is what happens to excess fat that you consume if you are in ketosis or thereabouts?
If you are actively metabolising fat and therefore not laying down fat what happens to fats that you eat that are not immediately needed? Is it possible to both lay down and metabolise fat at the same time?
If anyone has any technical explanations that would be great; it's the last link in the chain for me - I don't understand what the process is. By the way if you would like to explain why eating fat is a bad idea perhaps you could post that somewhere else?
Thanks
Dillinger
I think that, independent of whether you are in ketosis or not, your body is constantly burning off and laying down fat.
I think that the mistake is to think that your body fat is a big inert mass, and that you burn it off in the same order that you laid it down. I don't think it's true that the small bit of unsightly flab that you haven't been able to shift since 1977 is made up of the exact fat that you ate when you had a few extra chips with your kebab on the way home from watching STAR WARS.
Whether you eat it or not, most of your body's fuel needs are met by oxidising fat (dietary, stored body fat, or fat created from excess carbohydrate consumption). When you wake up in the morning your body is metabolising fat. After you've eaten your bacon and eggs it's probably laying some down.
I've written elsewhere that a non-athlete can't metabolise more than about 160g of carb a day, if you try to do more than that it either turns the carbs into fat, goes into "toxic emergency sugar burning mode" (insulin resistance yay!) or lets the the glucose accumulate in your blood (diabetes yay!). Most of that fat will be burned, some will be stored.
So, give or take 640kcal from glucose, your body is a fat burning machine. That's its preferred fuel source.
Ketosis works by replacing that 640kcal of glucose with fat and ketones (which are a bi-product of fat and protein burning). Instead of being fuelled entirely by glucose, your brain is fuelled almost entirely by ketones (plus about 25g of glucose). Your muscles change from burning a mix of fat and glucose to burning almost entirely fat.
The net result is that your are burning more fat, which you need to supply from either your post-STAR WARS flab or from your diet. Note that since you are no-longer eating carbs, that you also need to replace the carb created fat.
If you eat too much fat, even in ketosis, you will absolutely increase your reserves of body fat, but as I said above, from every mouthful you eat, some will be stored and some will be burned.