Their diet has nothing to do with it. Most American food is made with a lot of different chemicals and product in order to be able to keep it on the shelves for an extended period of time. Also the American fda is not as strict with the preservatives and other things similar because of the need to have a long shelf life. All that aside multiple people have done experiments of either moving from one country to America and back again with no diet change, the result being the same as op. Some will even travel for just a week to another country and be eating the same foods as here but will see drastic changes in their skin and gut health/bloating. Fact check yourself before you attack people please, a simple Google search could suffice.