>and it's VERY rare for our bodies to convert carbs into fat
Not THAT rare. Add alcohol, or just eat a whole lot of carbs and few fats[0].
[0]-http://examine.com/faq/how-are-carbohydrates-converted-into-...
Not THAT rare. Add alcohol, or just eat a whole lot of carbs and few fats[0].
[0]-http://examine.com/faq/how-are-carbohydrates-converted-into-...
Through a similar mechanism to alcohol, one can start up DNL much faster with large acute fructose consumption, but even in that "worst case scenario" we still only convert about 1% of surplus fructose into fat - http://www.nutritionandmetabolism.com/content/9/1/89
Somewhat ironically, a scenario where we make more fat from the carbs & protein we eat is when we consume very little fat. Eat less than 10% fat in your diet and this will cause DNL to ramp up. This is explained more in the "how we get fat" link in my previous comment.
Your last point was the main gist of my post, though I didn't spell it out so well. I didn't realize that about fructose though.