Body Mass--What Are the Tradeoffs

Interesting post by Stu Ellis at Farmgate on causes for food prices to increase.

I wonder--discussions of global food supply always pay attention to numbers of people, with some attention to the demand for better food when incomes increase. I wonder whether anyone has quantified the global human body-mass over time. I see the Latino construction workers laying the FIOS cable in my neighborhood and they're pretty uniformly small. (That's perhaps balanced out by how hard they work.) The Chinese in the 1970's were uniformly small, now they've got Yao Ming et. al. Diets make all the difference and allow differences in genetic endowments to be expressed.

Surely since WWII the average size of humans has increased significantly. If I remember, Gregory Clark's Farewell to Alms had some interesting data both on calories available to Westerners over the last 2-300 years and average height, but I don't think he had anything on waistline. Nor do I know how the reduction in physical labor and the increase in calories over the last 70 years fit together. Presumably the bigger the body, the more calories required to do x amount of work. So on a global basis, the per capita work has probably declined, and the per capita body has probably increased. Is it 6 of one, half dozen of the other? Inquiring minds want to know.