Researchers have found that keto and paleo diets score the lowest overall nutritional quality and have some of the highest carbon emissions.
According to a study, keto and paleo diets, as eaten by Americans, are the “least sustainable” and have the lowest overall nutritional quality.
The study, carried out by researchers at Tulane University, compared popular diets on both nutritional quality and environmental impact.
The keto diet (a diet that prioritises high amounts of fat and low amounts of carbs) was estimated to generate almost 3kg of carbon dioxide for every 1,000 calories consumed. Meanwhile, the paleo diet, (a diet that promotes the inclusion of natural fats from pasture-fed livestock, fish and seafood as well as nuts and seeds) received the next lowest diet quality score and also had a high carbon footprint, at 2.6kg of carbon dioxide per 1,000 calories.
The researchers analysed diet quality scores using data from more than 16,000 adult diets collected by the Centers for Disease Control and Prevention’s (CDC) National Health and Nutrition Examination Survey.
Study authors assigned individual diets point values based on the federal Healthy Eating Index and average scores were calculated for those eating each type of diet.
Commenting on the findings, the study’s senior author, Diego Rose, said that while researchers have examined the nutritional impact of keto and paleo diets, this is the “first study” to measure the carbon footprints of each diet, as consumed by US adults, and compare them to other common diets.
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“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,” said Rose.
In contrast, the researchers found a vegan diet to be the least impactful on climate, generating 0.7kg of carbon dioxide per 1,000 calories consumed. This is less than a quarter of the impact of the keto diet. The vegan diet was followed by vegetarian and pescatarian diets in increasing impact, according to the researchers.