I saw on the breakfast news yesterday morning a report about the biomass of humanity. What was particularly interesting was that the report made the connection between our eating habits and lifestyles and the effect we have on the planet. One of the report’s authors mentioned that when we think about our population we think only in terms of “mouths to feed”.  But as this report shows, when it comes to using the planet’s resources, not all mouths are equal.
The report, published here in BioMed Central, sets out the not very shocking observation that some countries’ populations are more overweight than others.  But this has an impact on our energy consumption. As the authors state:

“The energy requirement of each species...is a function of the number of organisms and their average mass.  In ecology, these factors are often considered together by estimating species biomass, the total mass of living organisms in an ecosystem. In relation to human populations, although much attention is given to the effect of population growth on food energy requirements, much less attention is given to the impact of increasing body mass.” Both resting and physical activity require more energy when you have a heavier body. Thus, the heavier the individual, the more energy is required. Similarly, the greater the biomass of humanity on this planet the greater our energy (food) requirements.  The report uses 2005 data and estimates that the global adult human biomass was then around 287 million tonnes. Of this, the biomass due to overweight and obesity (that is above a Body Mass Index (BMI) of 25) was 18.5 million tonnes – or 298 million people of average bodymass. That means that if everyone on the planet were to drop overnight to a BMI of under 25, then that would reduce our energy (food) consumption by 298 million average adults. 100% of the population cannot be thin of course, but if every country’s BMI was the same as that of Japan, then the global biomass would drop by the equivalent of 235 million people.  At the other end of the scale, if every country in the world was to become as fat as the USA, then the increase of biomass would be the equivalent of an extra 935 million people!
So, if we were all to adopt the American meal portion (which, because at heart I am still a boarding school boy, is still something that I am excited to try when I finally get to visit the Shining City on the Hill) then the extra food we would need to find would feed nearly a billion people.  You can see the difference in each continent’s obesity rates visually at the Economist’s neat little infographic here. 
It is good to read a report that suggests that population demands on food are not just a product of increasing population but also of lifestyle. After all, the greatest population increases in the coming years are to be in sub-Sahara Africa, not an area that is very overweight! As we have argued in this blog before, doomsday scenarios about growing population demands on resources often mask a desire for other people’s populations to be controlled, so that one’s own lifestyle can remain the same.