Which of these diets has the smallest carbon footprint?

KETO, paleo, vegetarian, pescatarian, vegan... In the last few years, approaches to eating that favor or eliminate the consumption of one or more foods have become commonplace when it comes to filling our plates. But how do they stack up in terms of their carbon footprint? A team of American researchers decided to investigate.

In your opinion, which diet is more polluting, the keto diet or the paleo diet? Researchers from Tulane University (New Orleans, USA) set out to provide a comprehensive answer to that question.

For this study the looked at data collected in a national survey conducted by the US federal health agency (CDC), consisting of the nutritional scores of more than 16,000 diets.

"Average daily greenhouse gas emissions in kilograms of carbon dioxide equivalents per 1000 kcal (kg CO2-eq/1000 kcal), were calculated for each diet" studied.

"Diet quality was determined using" various healthy eating indices, the study outlines. Once these diets were assessed, the researchers established a ranking from the most to the least polluting.

The keto diet, which is based around consuming fats in large quantities and carbohydrates in small quantities, generates nearly 3 kg of carbon dioxide for every 1000 calories consumed.

This diet was found to be the least environmentally friendly. It was followed by the paleo diet, which gives pride of place to proteins and plants, but which bans certain foods such as cereals and dairy products.

In terms of impact on the planet, its score is estimated at 2.6 kg CO2-eq per 1000 kcal.

The omnivore diet -- adopted by 86% of the participants in the survey -- is estimated to generated 2.23 kg CO2-eq per 1000 kcal.

Unsurprisingly, the vegan diet was found to be the least polluting of all: 0.7 kg of carbon dioxide per 1000 calories consumed, less than a quarter of the impact of the ketogenic diet!

The vegetarian diet was found to generate 1.16 kg CO2-eq per 1000 kcal.

"Our results highlight the nuances when evaluating the nutritional quality of diets and their carbon footprint.

On average, pescatarian diets may be the healthiest, but plant-based diets have lower carbon footprints than other popular diets, including keto- and paleo-style diets," the researchers emphasize.