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Study suggests global impact of obesity may be extra ~700MT/y CO2eq: about 1.6% of worldwide GHG emissions

A new analysis led by a team from the University of Copenhagen, Denmark, estimates that on a global scale, obesity contributes to extra GHG emissions of ~49 megatons per year of CO2 equivalent (CO2eq) from oxidative metabolism due to greater metabolic demands; ~361 megatons per year of CO2eq from food production processes due to increased food intake; and ~290 megatons per year of CO2eq from automobile and air transportation due to greater body weight.

Therefore, the researchers conclude, the total impact of obesity may be an extra emissions of ~700 megatons per year of CO2eq—about 1.6% of worldwide GHG emissions. Their open-access study is published in the journal Obesity, the flagship journal of The Obesity Society.

Meeting the needs of the increasing number of people on the planet presents a challenge for reducing total GHG burden. A further challenge may be the size of the average person on the planet and the increasing number of people with excess body weight.

… Inasmuch as obesity is an important contributor to global GHG burden, strategies to reduce its prevalence should prioritize efforts to reduce GHG emissions. Accordingly, reducing obesity may have considerable benefits for both public health and the environment.

—Magkos et al.

All oxygen-dependent organisms on the planet produce carbon dioxide as a result of metabolic processes necessary to sustain life. Total carbon dioxide production from any species is linked to the average metabolic rate, the average body size and the total number of individuals of the species.

To assess the impact of obesity on the environment, researchers used the standard definitions of obesity (body mass index of greater than or equal to 30 kg/m2) and normal weight (body mass index of less than 25). Calculations were made of the extra emission of greenhouse gases (carbon dioxide, methane, and nitrous oxide) from the increased oxidative metabolism, the increased food production and consumption and the increased fuel used to transport the greater body weight of people with obesity.

Compared with an individual with normal weight, researchers found an individual with obesity produces an extra 81 kg/y of carbon dioxide emissions from higher metabolism; an extra 593 kg/y of carbon dioxide emissions from greater food and drink consumption; and an extra 476 kg/y of carbon dioxide emissions from car and air transportation. Overall, obesity is associated with approximately 20% greater greenhouse gas emissions when compared to people with normal weight.

They caution that the estimates are not intended to be precise, but rather are crude estimates that involve the use of many assumptions and are only intended to be reasonable enough to demonstrate the potential impact of the effect of obesity on the environment.

The authors emphasize that it is critically important that this new information does not lead to more weight stigmatization. People with obesity already suffer from negative attitudes and discrimination, and numerous studies have documented several prevalent stereotypes.

This study makes it clear that we pay a steep price for making it difficult to access care for obesity. Not only does obesity affect the health of the individuals who have it, untreated obesity might also contribute to environmental issues.

—Ted Kyle, RPh, MBA, founder of ConscienHealth, who was not involved in the research

Physical activity is also associated with much more carbon dioxide being produced compared with rest, but no one will ever think of stigmatizing people who exercise for having a negative effect on the environment, according to Boyd Swinburn, MB ChB, FRACP, MD, FNZCPHM, in the School of Population Health at the University of Auckland in New Zealand. Swinburn wrote a commentary on the paper.

In the commentary accompanying the paper, Swinburn said the estimates add valuable information to the growing literature examining the nexus between obesity and climate change. He added, “while the contribution of obesity to greenhouse gas emissions is small, acting on the underlying drivers of them both is of paramount importance.”


  • Magkos, F., Tetens, I., Bügel, S.G., Felby, C., Schacht, S.R., Hill, J.O., Ravussin, E. and Astrup, A. (2020), “The Environmental Foodprint of Obesity.” Obesity, 28: 73-79. doi: 10.1002/oby.22657


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