Overweight populations could have the same implications for world food energy demands as an extra one billion people, researchers say after examining the average weight of adults across the globe.
Scientists from the London School of Hygiene and Tropical Medicine (LSHTM) say that tackling population weight is crucial for food security and ecological sustainability.
The United Nations (UN) predicts that by 2050 there could be a further 2.3 billion people on the planet and that the ecological implications of the rising population numbers will be exacerbated by increases in average body mass, researchers said.
The world's adult population weighs 287 million tonnes, 15 million of which is due to being overweight and 3.5 million is due to obesity, according to the study, which is to be published in BMC Public Health.
The data, collected from the UN and the World Health Organisation, shows that while the average global weight per person is 62kg in 2005, Britons weighed 75kg. In the US, the average adult weighed 81kg.
Across Europe, the average weight was 70.8kg compared to just 57.7kg in Asia.
More than half of people living in Europe are overweight (55.6 per cent) compared to only 24.2 per cent of Asian people. Almost three-quarters of people living in north America are overweight.
Researchers predict that if all people had the same average body mass index (BMI) as Americans, the total human biomass would increase by 58 million tonnes.
The authors of the study say the energy requirement of humans depends not only on numbers but average mass.
"Increasing biomass will have important implications for global resource requirements, including food demand and the overall ecological footprint of our species," they wrote.
"Although the concept of biomass is rarely applied to the human species, the ecological implications of increasing body mass are significant and ought to be taken into account when evaluating future trends and planning for future resource challenges.
"Tackling population fatness may be critical to world food security and ecological sustainability."
Professor Ian Roberts, who led the research at LSHTM, said:
"Everyone accepts that population growth threatens global environmental sustainability - our study shows that population fatness is also a major threat."
"Unless we tackle both population and fatness, our chances are slim."
Ella Pickover, Press Association Health Correspondent