If carbs make you fat why are there around a billion asians that live off carbs and are skinny. i doubt they all are hard workers?

Many work hard, and: They move more, as in walking here and there, plus up and down stairs. They eat fewer total calories. Weight gain is due to total net calorie intake (what you eat minus what you burn up). If one eats only carbs, but burns up the calories, he will not gain weight. The people who are eating more calories than they use, no matter where in the world they are, carbs or not, will always gain weight.