Originally Posted by
Radux
First off, omniscience, thanks for the post. You're right that I was probably a little to generic with my categorizing of how the body gets its energy.
You're completely correct that it will highly depend on the form of exercise and nutrition. Obviously if you're attempting to lose weight with minimal exercise and just do it through diet, that's when carbohydrates are the pure enemy.
Just by walking (or basically any aerobic activity) will promote the body to grab energy from fat, mostly due to oxygen always being present. Turn that the other way around (anaerobic exercise and no oxygen being present), the body immediately goes for glucose from food or your glycogen storage.
When I used to train people, I would highly recommend my clients to try a ketogenic diet along with a lot of weight lifting. That way, if they expend their glycogen stores, the body has no choice but to burn body fat. That's the point, right? Lose weight, lose fat, increase lean muscle mass: be healthy.
So yeah my bad on being a little too simplistic (I especially appreciate the biochemical aspect), but more often than not it's better to give general advise on a forum like this opposed to involving chemistry.