Study explores environmental “footprint” of obesity

The increasing average body size of people on Earth, in addition to the growing world population, may further challenge attempts to reduce man-made carbon dioxide emissions, according to a new paper published in the journal Obesity.

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.

People with obesity have greater carbon dioxide production from oxidative metabolism than individuals with normal weight. Further, maintenance of greater body weights requires more food and drinks to be produced and transported to the consumers. Similarly, transportation of heavier people is associated with increased consumption of fossil fuels. This results in additional carbon dioxide emissions related to food production and transportation processes. Globally, obesity was estimated to contribute to an extra 700 megatons of carbon dioxide emissions per year or about 1.6 percent of all man-made emissions, the researchers said.

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.

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, the researchers said.

To assess the impact of obesity on the environment, researchers used the standard definitions of obesity, a body mass index of greater than or equal to 30, and normal weight, a 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 kilograms per year of carbon dioxide emissions from higher metabolism, an extra 593 kilograms per year of carbon dioxide emissions from greater food and drink consumption and an extra 476 kilograms per year of carbon dioxide emissions from car and air transportation.

Overall, obesity is associated with approximately 20 percent greater greenhouse gas emissions when compared to people with normal weight, the researchers said.