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Study Finds Keto and Paleo Diets Have Highest Carbon Footprints, Vegan Diet Least Impactful

Researchers at Tulane University in New Orleans have conducted a study measuring the carbon footprints and nutritional value of six popular diets – keto, paleo, vegan, vegetarian, pescatarian, and the Mediterranean and DASH diets.[0] The analysis revealed that the keto and paleo diets, which prioritize high amounts of fats and low amounts of carbs (for keto) and eschew beans and grains in favor of meats, nuts and vegetables (for paleo), scored among the lowest on overall nutrition quality and had among the highest carbon footprints, with 3 kg and 2.6 kg of CO2 for every 1,000 calories consumed, respectively.[1]

On the other hand, the vegan diet was found to be the least impactful to the environment, generating only 0.7 kg of CO2 per 1,000 calories.[2] The pescatarian diet scored highest on nutritional quality, followed by vegetarian and vegan diets.

When those on omnivorous diets adopted the plant-forward Mediterranean or fatty meat-limiting DASH diet versions, both carbon footprints and nutritional quality scores improved.[3] Interestingly, pescatarian diets had the highest overall nutritional quality, ahead of both vegetarian and vegan ones.

According to a study supported by the United Nations in 2021, 34 percent of greenhouse gases are emitted from the food system.[4] Food production is responsible for a large portion of emissions, with beef contributing 8 to 10 times more than chicken and over 20 times more than nuts and legumes.[4]

Senior author Professor Diego Rose of Tulane University said that this is the first study to measure the carbon footprints of each diet, as consumed by U.S. adults, and compare them to other common diets.[4] He believes that the study raises important questions about how to encourage eating habits that are better for people and the planet and suggests that policymakers consider how different policies could affect outcomes and move us towards healthier, more environmentally friendly diets.[5]

0. “The carbon footprints of six popular diets – so how does YOURS stack up?” Daily Mail, 1 Mar. 2023,

1. “Study reveals the environmental impacts of various diets”, 1 Mar. 2023,

2. “Keto diet has highest carbon footprint and lowest nutritional value” Open Access Government, 2 Mar. 2023,

3. “How the keto diet compares to greener eating, in two charts” Insider, 3 Mar. 2023,

4. “Keto and Paleo Diets Are 4 Times Worse for Environment Than Vegan Diet” VegNews, 1 Mar. 2023,

5. “Keto and Paleo: the worst diets in both nutritional and environmental impact” ZME Science, 3 Mar. 2023,

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