They're burned off as the bodies main energy source.
That's a bit silly, don't you think? You are basically saying that we can eat all the carbs in the world, and everything is just magically burned? Nothing goes to fat cells. Only dietary fat goes to fat cells, carbs just raise the insulin and burn? Golly. Weren't you the guy who touted for calories in - calories out?
Do some research on how efficient DNL is in humans - we suck at it, basically.
I did this morning actually, since the topic caught my interest. There are quite a lot of inconclusive and contradictive research available off the subject. Some sources claim it's a relatively small function (like 4% of our BF or so), some studies find a bigger role from it. But it does exist, and it's not highly unlikely. Here's one study (Oh yeah, I'm picking the one that suits my view) http://www.ajcn.org/content/48/2/240.full.pdf
. It had people do a high-fat moderate protein diet to empty our glucose storages, followed by huge carbo loading phase. What happened was that fat was gained, and plenty. Maybe some from dietary fat, but not all of it. Here's a snappy picture:
The more I researched, the more I came to be inconclusive about the issue. Lipogenesis is a real thing, it does have an effect however. No studies have denied that. It's the amount of DNL that is happening that's still a bit in the shadows for me. But saying it's highly unlikely is a bit rough to my ears.
It's that the carb intake 100% stops fat oxidation that causes us to gain weight (all the fat we eat, stored as fat.)
I'm still not buying this. Sure, it's true, there's no doubt that insulin and other silly hormones have that kind of main function. BUT, I think we shouldn't totally exclude dietary carbo control. Carbs are also participating in fat storaging process, as glucose is used to form triglycerols. Glucose is burned to get glycerol phosphate, which is needed to create TAG. Hence = More carbs = more fat. BUT, I'm aware that this process isn't exactly the point you are trying to imply. Just wanted to mention it as well. Carbs do participate in fat gains more than just hormonally.
Protein also has to be converted to glucose and then fat before it can be stored.
And that is also more than possible. You can eat too much of everything. Glucose can be turned into fat, and Carbs and protein are, for what I know, quite easily worked into glucose.
Let me rephrase what I was saying - as i never said it was impossible, I just said that it was highly unlikely.
The fat that's gained from increased carb intake is usually a factor of dietary fat being stored due to fat oxidation coming to a halt.
Also, you can clearly see in that diagram that DNL doesn't occur much until consistently eating 500+ grams of carbs a day for over a week straight.
Obviously, I wouldn't recommend anyone eating that many carbs.
The point I was making is this, as this thread is all over the place at the moment:
Dietary fat is the macro most easily stored as fat - it's that simple, our body has no problem storing it as fat.
Carbohydrates are RARELY stored as fat unless extremely large amounts are eaten (ie, 500+ grams a day). If you eat excess calories, more than likely it's the dietary fat that is actually stored if you're eating moderate carbs. Does it matter which macro is being stored? Not really, it's still eating calories over maintenance that cause it.
Protein is also nearly never stored as fat - in cases of overeating, fat/carbs are always the first choice to be stored as fat. Gluconeogesis I'm pretty sure is non-existent when in a surplus of calories, I'm fairly certain that protein oxidation just increases similar to the way that carb oxidation does when it's ingested. Funny enough, excess dietary fat does nothing to increase fat oxidation.