Forget counting kJs - Protein and carbs are the key to a longer life

The research marks 80 years since the publication of a paper showing that restricting kilojoule intake prolongs lifespan.

“We have known for many years that kilojoule restriction diets increase lifespan,” said Professor Stephen Simpson, Academic Director of the Charles Perkins Centre.

“However, except for the fanatical few, no one can maintain a 40 per cent kilojoule reduction in the long term, and doing so can risk loss of bone mass, libido and fertility.”

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The research showed in mice that a low protein, high carbohydrate diet provides the same benefits as kJ restriction - a result researchers believe may also hold true in humans.

“There is one downside. While a low protein, high carb diet is likely to have beneficial effects later in life, it is also associated with an increased food intake driven by protein appetite, which poses the risk of weight gain."

“It still holds true that reducing food intake and body weight improves metabolic health and reduces the risk of diseases like type-2 diabetes, obesity and fatty liver disease.

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“However, it appears that including modest intakes of high quality protein and plenty of healthy carbohydrates in the diet will be beneficial for health as we age.”

“We’ve shown that when compared head-to-head, mice got the same benefits from a low protein, high carbohydrate as a 40 per cent kilojoule restriction diet. If the same applies to us, this would mean healthier ageing, with more pleasure and less pain than caloric restriction.”

The results follow research from the Charles Perkins Centre that showed a low protein, high carbohydrate diet promotes longevity and good cardiometabolic health, while a high protein, low carbohydrate diet leads to leaner body mass and better measures of reproductive function, but also shortened lifespan and poor cardiometabolic health.

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The game-changing body of work points to the balance and quality of protein, carbohydrates and fat - rather than kilojoule intake or the role of any one nutrient - as the major factor in nutritional health.

“We have again shown that changing the macronutrient composition of a diet is vitally important, and in this case is a more feasible intervention than kilojoule restriction for managing human health,” Professor Simpson said.