The human body and its design is much more complex than often we recognize when we attempt to understand its workings. If fact this is really the case with all of creation.

Focusing solely on calories and metabolic rate can be misleading as to why one population is less healthy/obese than another.

In Dr. T. Collen Campbells (http://www.tcolincampbell...) research career he began to realize that the body is using a symphony of nutrients to perform a multitude a very complex functions to perform as it was intended to.

Examining Dr. Cambell's China Study (http://thechinastudy.com/...) his research suggests the major differences in health (including obesity) between rural Chinese and US population is due to what they are eating and not solely to the amount.

American's by not eating what their bodies were designed to eat and throwing their whole system in chaos, initiating all kinds of diseases including obesity.

I would say in this study as with the rural Chinese at the time of The China Study the subjects are eating food more in line with what their bodies have been designed to utilize thus they are healthier including not being overweight.

It is not just how many calories the human body takes in but what form they are coming into the body as. While studying this does provide some insight that metabolic rate between the different populations very similar my fear is as the public hears they will focus on calorie intake and keep bringing in calories into their bodies via the same foods that are making them sick and fat.
I have a had friend who is a nurse who was told by a doctor that he has lost weight eating just marsh mellows, making sure amount of calories was below his metabolic rate. Even as a nurse she bought into this. Many of health professional are not truly educated in nutrition.