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Quiz: How Does Your Diet Contribute to Climate Change?






On any day, those meal choices would likely land you among Americans whose food-related climate impacts are:

Your climate-impact category is based on research from Tulane University and the University of Michigan that examined greenhouse gas emissions associated with food choices made by more than 16,000 Americans during a single day.

Researchers ranked participants’ diets by carbon footprint and divided people up into five equally sized groups. They found that Americans with the highest-impact diets were responsible for five times more overall emissions in a day than the Americans with the lowest-impact diets.

Percent of Americans

in each climate-impact group

Percent of total U.S. food-related emissions they’re responsible for

Percent of Americans

in each climate-impact group

Percent of total U.S. food-related emissions they’re responsible for

Note: The data reflect self-reported, one-day diets. Standardized per 2,000 calories.

Previous studies have mostly focused on emissions from the average American diet, but “we thought it would be very interesting to know the impacts of individual diets,” said Diego Rose, a professor of nutrition at Tulane University and lead author of the study. “Then we could say: Are climate-friendly diets healthier or not? Who is more likely to eat a climate-friendly diet?”

Dr. Rose and his colleagues found that, in general, diets with a smaller carbon footprint were indeed healthier than those with a large one. (That’s “a double win: better for the environment and better for health,” he said.) Women were more likely to eat these low-impact diets than men, as were African-Americans compared with whites. The study did not find significant differences between groups based on income or education.

While low-impact diets were found to be healthier on average, the healthfulness of foods and their carbon footprint aren’t always in sync. Processed foods and sugars have a lower climate impact than a steak dinner, but that doesn’t mean you should eat more of them, Dr. Rose said.

This research “helps us understand the landscape of what’s possible” when it comes to shifting American consumption patterns, said Roni Neff, director of Johns Hopkins’s Food System Sustainability and Public Health Program, who was not involved with Dr. Rose’s work.

She said that convincing the fifth of Americans in the high-impact group to cut back on beef, dairy and other carbon-heavy foods is crucially important because of that group’s outsize impact on overall emissions. But, because 80 percent of Americans fall in one of the other categories, “we can’t ignore them either,” she added.

It’s worth remembering that the classifications in this quiz are shown relative to other Americans. The average American is responsible for more diet-related greenhouse gas emissions than the average Briton or German – and Americans’ climate impact is much larger when compared to residents of most developing countries.

Changes in consumer demand will play a key role in lowering food-related emissions enough to avoid the worst effects of climate change, according to a landmark report released earlier this year, but the supply side – including production, processing and retail – needs to become more sustainable too.

This calculator compares the impacts of individual food choices based on a 2,000-calorie-a-day diet, but how much food you consume and how much you waste also add to your dietary footprint. Many Americans eat more calories and protein than they need per day, according to a recent study from the World Resources Institute, so limiting overconsumption alone could put a dent in food-related emissions. Americans also throw out about a fifth of the food they buy.

“To make the biggest individual difference, people should focus on all three things,” Dr. Rose said. “Eat less beef or ruminants, don’t overeat and don’t waste food.”

The data used to make this calculator is based on research by Diego Rose and Amelia Willits-Smith from Tulane University’s School of Public Health and Tropical Medicine, and Martin Heller and Robert J. Meyer from the Center for Sustainable Systems at the University of Michigan, including a study published in The American Journal of Clinical Nutrition in January 2019. The research was supported by a grant from the Wellcome Trust.

Self-reported one-day diets came from the National Health and Nutrition Examination Survey. For the majority of foods, greenhouse gas emissions are based only on agricultural production. Processing emissions were only captured for some foods, such as flours, sugars, oils, cheese, yogurt, tofu, carbonated beverages and beer. A majority of all emissions in the food sector come from agricultural production.