They found that low-carb diets that involved people consuming animal-based proteins and fats were linked with a greater risk of early death, but low-carb diets that involved people consuming plant-based proteins and fats were linked with a reduced risk of early death.
Moderate carb intake - where people ate between 50-55% of energy from carbs - was found to slightly lower the risk of death compared with low (30% or less) and high (65%) carb diets. Alternatively, if restricting carbohydrate intake is a chosen approach for weight loss or cardiometabolic risk reduction, replacement of carbohydrates with predominantly plant-based fats and proteins could be considered as a long-term approach to promote healthy ageing.
"Low-carb diets that replace carbohydrates with protein or fat are gaining widespread popularity as a health and weight loss strategy", said study leader Dr Sara Seidelmann, Clinical and Research Fellow in Cardiovascular Medicine from Brigham and Women's Hospital, Boston.
"Whereas those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality".
For a longer, healthier life, it's best to eat carbohydrates in moderation.
However, she said, "our data suggests that animal-based low-carbohydrate diets, which are prevalent in North America and Europe, might be associated with shorter overall life span and should be discouraged".
The study, led by Harvard School of Public Health in the USA, goes some way to ending the decades-old debate over whether cutting carbs or fat is a better way to lose weight and improve health.More news: Sarri identifies exactly where Chelsea need to improve after win over Arsenal
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The researchers also pulled data from seven other studies involving more than 400,000 people in 20 countries. The participants had to self-report their diets, based on which the researchers estimated the proportion of calories they got from carbohydrates, fats, and protein.
In the study, published in The Lancet Public Health, 15,400 people from the USA filled out questionnaires on the food and drink they consumed, along with portion sizes.
Of course, this is just one study, and lots more research would have to be done to conclude that loading up on carbs is better that cutting them out altogether.
Food plans which replace carbs with protein and fat, such as the Ketogenic or Atkins diets, have gained popularity, and endorsed by celebrities such as Gwyneth Paltrow and Kim Kardashian.
As a caveat, there are some limitations to this study.
The study relied on people remembering the amount of carbohydrates they ate.
The study authors noted, however, that the participants' eating habits were self-reported and only assessed at the start of the study and six years later.
Catherine Collins, an NHS dietitian, said: "No aspect of nutrition is so hotly contended on social media than the carb versus fat debate, despite the long term evidence on health benefits firmly supporting the higher carb argument".