New study says obesity increases greenhouse gases

A new study published in the journal Obesity may indicate that increasing body weight trends among humans, as well as the increasing number of people living on earth, could push back efforts to reduce carbon dioxide emissions of human origin.

The paper explains that all living things on earth that use oxygen also produce carbon dioxide from the various bodily mechanisms that keep life going. The metabolic rate, the body size and the number of individual members of any given species contribute to the total production of carbon dioxide from that species.

Image Credit: Suzanne Tucker / Shutterstock
Image Credit: Suzanne Tucker / Shutterstock

Factors linking obesity to greenhouse gases

When it comes to humans, obese people produce more carbon dioxide as a result of using up oxygen to run various bodily functions, compared to those with lower weight. The heavier you are, moreover, the more food is required to keep you heavy – which means more food and drink must be manufactured and bought to the final consumption point. Heavier people also require more fuel consumption for their transportation, which means still more carbon dioxide is formed from food production-related emissions, as well as from the vehicles used to carry such foods to them. All over the world, obesity costs earth about 700 megatons of emissions each year, which comes to about 1% of manmade emissions.

The science linking obesity and emissions should not cause fat people to feel further discriminated against. Many studies have shown that obesity is often the subject of stereotypes, and much mockery as well as stigma.

Instead, the researchers choose to treat obesity as an unfortunate health event which is treated like any other. Says Ted Kyle, an expert observer, “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.”

Supporting their view, an expert commentator, Boyd Swinburne, says that nobody would blame people who exercise for their contribution to overall carbon emissions, which is unquestionably greater than for sedentary people. The message that the study seeks to pass on is that the proper management of obesity is not only good in terms of reducing the rates of illness, death and health-related expenses, but also in relation to environmental benefit. Researcher Faidon Magkos says, “This has important implications for all those involved in the management of obesity.”

The methods

How did they arrive at their conclusions? The researchers in the current study resorted to the standard definitions for obesity, namely, a body mass index (BMI) of 30 kg/m2 or more. Normal body weight was defined as usual, a BMI of below 25. They then calculated the excess greenhouse gas emission (including methane, carbon dioxide, and nitrous oxide) that would occur due to the increased consumption of oxygen in the metabolism of an obese individual, the excess emissions due to the higher demand for food and beverages, which need to be produced in excess of normal, and the excess fuel required to carry around more bulky people.

The findings

They found that each obese individual on average had 81 extra kg/year of carbon emissions due to increased oxygen consumption via metabolism. In relation to the excess consumption of food and drink, the carbon emission exceeded that of a normal individual by over 590 kg/year. Transportation of the greater body weight cost another extra 476 kg/year of emissions from car or air transport. Thus, obese individuals produce about a fifth more greenhouse gases than those with normal body weight.


These are estimates, emphasize the researchers, who explain, “Harmonizing data from epidemiology (prevalence rates of obesity), physiology (total energy intake and expenditure) and environmental science (carbon dioxide emissions from different sources) is not a straightforward task.” Their aim was to help understand the environmental impact of obesity via a reasonable estimate rather than a precise figure. Swinburne says this type of estimate should give this paper value in terms of exploring the link between climate change and obesity. The most important step is to understand what drives increasing emissions as well as increasing body weight.

Journal reference:

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,

Dr. Liji Thomas

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.


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