>I don't think the liver "decides" whether to turn food energy into glycogen
>or fat. It may be the liver that converts food energy to glycogen or fat. If
>your glycogen stores are depleted in your muscles or your liver, then the
>food energy goes to replenish them. But if they are not depleted, how can it
>store any more glycogen there?
The control of the various enzymes for glycogen synthesis and breakdown, for
fat synthesis and breakdown, and for glucose production are part of one of
these typically complicated feedback systems. Most of this stuff takes place
in the liver and that's what I meant by "decides". Glycogen stores don't
have a strict maximum, it's just that the more of it there is, the more the
enzymes tend to break it down and the less they tend to make it.
>As i understand it, if you exercise and deplete your glycogen stores, then
>when you eat the food energy will be preferentially used to replenish them.
>If you have not been exercising and your glycogen stores are not depleted,
>then if you eat a bid meal (especially one with a lot of carbs) the food
>energy will be stored as fat.
This is basically what's going on, except that I've never seen any indication
that the liver cares all that much about the type of food coming in. The
liver is very good at interconverting the 3 forms (protein, carbohydrate, and
fat) and normally interconverts all of them all of the time. The associated
energy loss is apparently negligeable.