Originally Posted by Silock
I know the book says I can use fruits exclusively for carbs on non-workout days. I'm just wondering how that works to fill muscle glycogen when fructose preferentially fills liver glycogen. After filling liver glycogen, does the excess get converted to muscle glycogen? Or does it go toward fat? A combination of both?
I can't really find a specific answer to this on the main site or in the book.
I'm okay with knowing that I *can* do this; I'm just wondering *why* I can do it.
My understanding is that the problem with fructose is the overconsumption of foods where HFCS has been used as a sweetener. The amount of fructose in fruit is not significant enough to cause extreme metabolic changes. So if you are dieting and eating mostly fruit you shouldn't have a problem losing weight.
The problem with HFCS is that people consume a lot of it. And, because HFCS has a higher ratio of fructose to glucose than sucrose does (sucrose, remember is a disaccharide of fructose and glucose), there is the problem that fructose metabolism in the liver will not be regulated. This will cause the fructose to be oxidized to 2 pyruvate, which can be further oxidized to 2 acetyl-CoA, which can be used to make fatty acids. Presumably, if someone eats lots and lots of sucrose, there would be the same issues, since the person is taking in more fructose and glucose that would be healthy for them.
Fruits are okay, since the amount of fructose is not all that high, and the fruits have other molecules that provide a nutritional benefit.