Fad diets are recognized as the worst for the climate

A new study compares the carbon footprint of different eating models.

According to research, the ketogenic diet produces the most greenhouse gases per 1,000 calories (2.9 kg). Additionally harmful to the environment is the paleo diet. A vegan or vegetarian diet is linked to the least amount of greenhouse gas emissions.

Researchers from Tulane University in New Orleans compared the carbon footprint of the six most popular diets in the US. The worst diets in terms of impact on greenhouse gas emissions were the ketogenic diet and the paleo diet, while plant-based diets were the best in terms of climate impact. This suggests that to eat healthy without destroying the planet, we should all eat more plant-based foods.

Carbon footprint comparison of six popular diets—a new study

Nutrition is an important part of figuring out how good a diet is for the environment because it has a big effect on greenhouse gas emissions.

Model diets assume adherence to macronutrients and recommendations, but nutrition does not look like that in practice.

Scientists from New Orleans collected data from 16,6 US residents to compare the carbon footprint of different nutritional models.

  • keto diet,
  • paleo diet,
  • pescatarian diet,
  • vegan diet,
  • vegetarian diet,
  • diet of “omnivores”—without exclusions and restrictions.

Researchers calculated the CO2 emissions of a diet per 1000 kcal to measure its contribution to greenhouse gas emissions.

Carbon footprint of individual diets per kg of CO2 emissions for every 1000 kcal:

  • ketogenic diet: 2.91 kg CO2 per 1000 kcal;
  • paleo diet: 2.6 kg CO2/1000 kcal;
  • Omnivore diet: 2.23 kg/1000 kcal;
  • pescatarian diet: 1.66 kg/1000 kcal;
  • vegetarian diet: 1.16 kg/1000 kcal;
  • vegan diet: 0.7 kg/1000 kcal;

The worst and best diets for the climate

The ketogenic diet was recognized as the worst diet in terms of impact on CO emissions due to its high amount of meat, fish, fat, and cereal carbohydrates. The paleo diet, also known as the diet of our ancestors, has more carbohydrates and focuses on making the products less processed, but it contributes to a significant emission of CO2.

People on plant-based diets reduce greenhouse gas emissions by reducing meat and animal products, which can be seen in the carbon footprint of their menus.

The best diet for climate vs. the best diet for health

The table below shows the classification of diets from worst to best in terms of carbon emissions and health effects.

ClassificationImpact on CO2 emissions (from largest to smallest)Health effects (from worst to best)
1Ketogenic dietKetogenic diet
2Paleo dietPaleo diet
3Omnivores dietOmnivores diet
4Pescarian dietvegan diet
5vegetarian dietvegetarian diet
6vegan dietPescarian diet

As you can see, a good compromise between the healthiness of the diet and its impact on the climate is the use of plant-based diets with the addition of fish and seafood.


O’Malley K., Willits-Smith A., and Rose D. Popular diets as selected by adults in the United States show wide variation in carbon footprints and diet quality. Am J Clin Nutr. 2023 Feb 20:S0002-9165(23)00511-7. doi: 10.1016/j.ajcnut.2023.01.009.

“Modna Dieta Uznana Za Najgorszą Dla Klimatu. Nowe Badanie Porównuje Ślad Węglowy Różnych Modeli Odżywiania – Polki.pl.” Polki.pl, 10 Mar. 2023, polki.pl/dieta-i-fitness/zdrowe-odzywianie,dieta-a-emisja-gazow-cieplarnianych-i-ekologia-porownanie-sladu-weglowego-6-popularnych-diet,10449863,artykul.html.


Author: DoctorMaryam.org

4th Professional Medical Student. Karachi Medical and Dental College.

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