some expats (not all) do some kind of excersise get out the car and do there own shopping and carry it to the car, run around after their own children , pick up and and do some of the cleaning in their own house. Make their own food for dinner,go to work etc. But there are hardly any locals that do this because they have other people to do it for them. So if you never have to exert yourself you will naturally put on weight.