Though eating a lot but still thin

Though eating a lot but still thin - Wonder it, but every day eating a lot, but still thin and weight is not up-rise. Not that our friends who only eat a little skinny. This can be influenced by several factors, what are the factors? Here as in the following reports from eHow.GenIf your parents or your grandparents every skinny, so you can go too thin due to hereditary factors. This is caused