A lot if also down to the proportion of the three food groups that we eat. The amount of refined carbohydrate in the diet has increased drastically.

There have been plenty of studies following natives who moved to the cities and suddenly they had a weight problem, not sure to the amount they were eating, but due to the different make up of the diet. Aboriginies are known for being overweight when fed a wester diet, but back on their native diet they don't have a problem.

I am of the opion that we should eat like our ancestors as that is what the body evolved to eat. Meat, fish and some fruit and nuts. No refined grains and no sugar.

Peoples tastes have changed as well - think of all the marketing the large shops do to get us to eat "super sweet" sweet corn and peas and other veg.