Different ethnic groups have a greater, probably genetic, propensity for putting on weight, developing diabetes, strokes and a number of other such conditions, but I am sure that "grazing" and over large portion sizes makes the problems of being overweight worse.
As Mamie says the food industry really adds to this problem supermarkets are always advertising food stuffs as "ideal for snacking".
We really did not see so many very overweight people in the 50s and 60s.
I doubt if the food industry would appreciate any legislation on reducing portion size, or controlingg their heavy promotion of snack foods.