When your default state is starvation, staying lean is easy. If you look at statistical measures of height, the average height of most human beings continued t

When your default state is starvation, staying lean is easy. If you look at statistical measures of height, the average height of most human beings continued to increase until the mid 1980s whereupon it plateaued in many countries. What this tells you is that vast majority of people, even in the "First World" were nutritionally deprived until the mid 1980s. Which, gee, would you look at that, is considered to be the start of the "obesity epidemic". As such, the answer to the obesity epidemic is obvious: simply starve people again.