Time to veto keto? Study reveals the nutritional value and carbon footprints of six popular faddy diets – so how does YOURS stack up?

Most of us try to stay healthy by maintaining an active lifestyle and keeping a close eye on what we put into our bodies.

But what we eat also has an impact on the environment, with the carbon footprints associated with different foods varying considerably.

Researchers at Tulane University in New Orleans have calculated the carbon footprints of six popular diets, and compared these to their nutritional values.

The popular ketogenic, or ‘keto’, diet, which involves replacing carbohydrates with fat, was found to be both the least sustainable, and to have the lowest nutrition quality. 

At the other end of the scale, the vegan diet was found to have the lowest carbon footprint, while a pescatarian diet was the best in terms of nutrition. 

The popular ketogenic, or ‘keto’, diet, which involves replacing carbohydrates with fat, was found to be both the least sustainable, and to have the lowest nutrition quality (stock image)

In the study, published today in The American Journal of Clinical Nutrition, the researchers set out to assess the environmental impacts and nutritional qualities of complete diets, as opposed to just individual food products.

Six popular diets were included in the study. 

These were pescatarian (fish on top of a vegetarian diet), vegetarian (no meat, fish or chicken), vegan (no foods derived from animals), omnivore (meat-eaters), paleo (fruits, vegetables, lean meats, fish, eggs, nuts and seeds), and keto (replacing carbohydrates with fat). 

According to Dr Diego Rose, senior author of the study, this is the first study to compare the carbon footprints of the keto diet and paleo diet to those of other eating plans.

The nutrition professor said: ‘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.’

To assess the nutritional value of each diet, the researchers used the National Health and Nutrition Examination Survey, which is run by the national public health agency in the US. 

Individual health scores were assigned to the diets of 16,000 surveyed adults, and then averaged for each of the six diet categories to give their Healthy Eating Indexes.

The pescatarian diet was deemed the best (58.76/100), followed by the vegetarian diet (51.89/100) and vegan diet (51.65/100). 

Meanwhile, the omnivore diet scored 48.92/100, the paleo diet 45.03/100 and the keto diet brought up the rear with a score of 43.69.  

The carbon footprint values for each diet were then calculated using emissions data from life cycle assessments of over 300 commodities.

The carbon footprint values for each diet were calculated using emissions data from life cycle assessments of over 300 commodities

While, as suspected, the vegan and vegetarian diets came out first and second for sustainability, a pescetarian diet actually beats them on nutritional value  (stock image)

The scores were given as the mass of carbon dioxide produced for every 1,000 calories consumed by the person following that diet.

The results revealed that the keto diet has the highest carbon footprint (6.4lbs), followed by the paleo diet (5.8lbs) and omnivore diet (4.9lbs). 

In contrast, the vegan diet had the lowest carbon footprint (1.5lbs), followed by the vegetarian diet (2.6lbs) and pescatarian diet (3.7lbs).  

The omnivore diet, which has no restrictions, is by far the most common, and was followed by 86 per cent of survey participants.

But if only a third of those people switched to vegetarianism, they would cut out emissions equivalent to 340 million passenger vehicle miles a day, according to the study. 

While, as suspected, the vegan and vegetarian diets came out in first and second place for sustainability, a pescetarian diet actually beat them on nutritional value.

However, all three were still healthier than the omnivore, keto and paleo diets, with the latter two bearing the lowest diet quality scores.

To assess the nutritional value of each diet, the researchers used the National Health and Nutrition Examination Survey, which is run by the national public health agency in the US

Next, Dr Rose wants to investigate how different policies could encourage eating habits that are both healthier and more environmentally friendly.

‘Climate change is arguably one of the most pressing problems of our time, and a lot of people are interested in moving to a plant- based diet,’ he said. 

‘Based on our results, that would reduce your footprint and be generally healthy.

‘Our research also shows there’s a way to improve your health and footprint without giving up meat entirely.’

A recent study has found that consumers are less likely to buy packets of meat when they have labels with ‘meat-shaming messages’ and gruesome images.

Research has also shown that giving ‘eco-labels’ to options on a menu caused diners to choose a more sustainable meal from a takeaway restaurant. 

Would these labels put YOU off your chicken? Scientists say gruesome cigarette-style warnings on MEAT could be used to shame buyers 

We’re all used to seeing the gruesome images of black lungs and rotting teeth on packets of cigarettes, designed to put smokers off the unhealthy habit.

Now, scientists say that slapping similar stickers on packs of meat in supermarkets could help to shame buyers.

The stickers could include sad images of animals, accompanied by messages such as: ‘Animals suffer when you eat meat.’ They could also include images of decimated forests with the words: ‘The Amazon rainforest is destroyed when you eat meat.’

A study from Delft University of Technology in the Netherlands found that consumers were less inclined to buy products featuring the labels.

‘Meat-shaming messages trigger shame but also other negative emotions that translate into reduced purchase intentions,’ the authors wrote. 

Read more here 

A study from Delft University of Technology in the Netherlands found that consumers were less inclined to buy products featuring the ‘meat-shaming’ labels