Of the six popular diets analysed, Keto and paleo were found to be the least sustainable and to have the lowest diet quality scores.

The popular Keto and paleo diets are among the least nutritious and environmentally friendly, a new study by Tulane University researchers found.

Keto dieters consume a lot of protein in place of carbohydrates like bread, spaghetti, potatoes, and rice. It causes the body to enter a condition known as ketosis, which happens when a person is starving or fasting and uses fat for energy.

Meanwhile, only foods that might have been hunted, fished for, or gathered during the time of the cavemen are allowed in the paleo diet. They consist of nuts, seeds, fruit, vegetables, meat, fish, eggs, herbs, and spices.

Processed foods like cakes, pastries, biscuits, and chips are eliminated from both trendy diets. The keto diet has been tried by many celebrities, including Gwyneth Paltrow, Halle Berry, and Kim Kardashian, while the paleo diet has been tried by Miley Cyrus and actress Uma Thurman.

“We suspected the negative climate impacts because they’re meat-centric, but no one had really compared all these diets – as they are chosen by individuals, instead of prescribed by experts – to each other using a common framework,” says senior author Professor Diego Rose of Tulane University in a media release.

The first study of its sort discovered that the keto and paleo diets include the least vitamins, which is unfortunate for those who try these diets. The greatest carbon footprints are produced by the keto and paleo diets, which produce nearly three and 2.6 kg of carbon dioxide for every 1,000 calories ingested, respectively.

Pescatarians, those who primarily eat fish, do the best in terms of health and vegetarians and vegans follow soon after.

With 0.7 kg of emissions, or less than a fourth of those from the keto diet, researchers discovered that a vegan diet has the least negative effects on the climate. With regard to environmental friendliness, the vegetarian and pescatarian diets come in second.

The study, which surveyed more than 16,000 adults conducted across the United States, and was published in The American Journal of Clinical Nutrition, used a point system based on the federal Healthy Eating Index to allocate points to specific diets.

For individuals following each diet, average results were computed.

Omnivores, who consume both meat and vegetables, made up the majority of participants (86%) and were the most prevalent group. They were in the middle of the pack in terms of sustainability and quality.

According to the study’s authors, if a third of the participants went vegetarian for just one day, it would save 340 million miles driven by people in cars. Both carbon footprints and nutritional quality scores increased when they chose the DASH or Mediterranean diets, which limit fatty meat.

According to the UN, the food industry is responsible for a third of greenhouse gas emissions. Particularly, the beef industry generates up to ten times as many emissions as the chicken industry and more than twenty times as many as the nut industry.