Yes, that is exactly the problem. They do not have diets loaded with processed sugar and flour products like we do here. Refined carbs are made from processed flour and sugar and create an insulin response in the body that prevents fat burning. The good carbs are vegetables, fruits, nuts, beans and legumes.
Here is a pretty good explanation written by a cardiologist who once worked for Atkins: http://www.wlbt.com/Global/story.asp?S=377377&nav=2CSQ5wO13Uqa