LINDA WERTHEIMER, HOST:
Now, for a global perspective on our national weight problem. The number of humans on the planet is now more than seven billion. And our total weight is 287 million tons. That number comes from a new study that suggests weight, not just headcount, should be considered when looking at the impact of people on the planet.
To find out more, we called Ian Roberts. He's a professor at the London School of Hygiene & Tropical Medicine, and is the lead author of this study.
Good morning, Professor Roberts.
DR. IAN ROBERTS: Good morning.
WERTHEIMER: So why is it important to factor in weight - and just to be clear, in this total number you're not talking about obesity, you're talking about overall weight, right?
ROBERTS: Yes. I mean, basically people always start thinking, well, you know, we're damaging the Earth's ecosystems from our sort of polluting activities and so how many people can the Earth support? And then immediately they start thinking about the numbers of people on the planet, you know, how many mouths to feed? But the point of this paper is actually food doesn't feed mouths, it feeds flesh. So the really important question is not how many mouths there are, it's how much flesh there is. And it's important to do that because if you're only thinking about numbers of mouths, we immediately start thinking about poor women in Africa having too many babies but population fatness is a big problem too.
WERTHEIMER: Now, your tables show that North Americans are the heaviest - and while we make up 6 percent of the population of the Earth, our obesity rate is such that we make up a third of all the excess weight. Now is that just another way of saying that we're obese, which I think we already know from a whole lot of reports, but is there some other implication?
ROBERTS: When the media talk about obesity in the United States, they always talk about certain individuals that have this problem, obesity, but what they miss is actually the whole population is getting fatter - even the thin people are getting fatter. So we worked out that if every country in the world had the same body mass index distribution as the United States, in mass terms it would be like having an extra billion people in the world. So there's obviously an increased demand on food supplies, but also there is an increased demand on everything. You know, bigger people need more energy to move them. Airplanes take more energy to get off the ground. It takes more of the shares that, you know, of the Earth's resources to actually support all that extra weight.
WERTHEIMER: You know, looking at your list, your chart of overweight and obese countries, the U.S. is number one followed by Kuwait. Can you explain why?
ROBERTS: Well, the U.S. is number one and then we've got a lot of the Arab states in the rest of the leader pack, if we can call it that. And what's common between those is actually the price of gasoline is very low. So where gasoline is really cheap, we over-consume it, it's bad for the environment and actually because we should be using food energy for human movement - if we use gasoline for human movement, then we store the food energy and you know where we store it.
WERTHEIMER: Yes. I'm afraid I do.
ROBERTS: No. I'm not being personal.
(LAUGHTER)
WERTHEIMER: Ian Roberts is a professor of epidemiology and public health at the London School of Hygiene and Tropical Medicine.
Professor Roberts, thank you very much.
ROBERTS: Thank you. Bye-bye. Transcript provided by NPR, Copyright NPR.