The truth about calories

World-first research by the Charles Perkins Centre has found that the interaction between calories has enormous significance for our health.
Professor Steve Simpson

Professor Steve Simpson

Within weeks of its hub opening for research and teaching earlier this year, the Charles Perkins Centre hit the headlines with groundbreaking research into the impact of protein, fat and carbohydrate on diet and nutrition.

The world-first research was conducted by Professor Steve Simpson (pictured above), the centre’s Academic Director, and his colleagues Professor David le Couteur (leader of the Project Node in Translational Gerontology) and Professor David Raubenheimer (the centre’s Nutrition Theme Leader) as part of the translational gerontology research node at the centre. They found that restricting calorie intake had no benefit on lifespan, in mice at least.

The results of their research, which examines the effects of the balance of protein, fat and carbohydrate on metabolic health, ageing and longevity in mice, were published in March in the prestigious scientific journal Cell Metabolism. Their work showed that:

  • A high-protein, low-carbohydrate diet resulted in reduced body fat and food intake but also led to a shorter lifespan and poor cardiometabolic health.
  • A high-carbohydrate, low-protein diet resulted in longer lifespan and better cardiometabolic health, despite also increasing body fat.
  • A low-protein, high-fat diet provided the worst health outcomes, with fat content showing no negative influence on food intake, leading to obesity.
  • Food intake is regulated primarily by dietary protein and carbohydrate, and not by the number of calories consumed.

“To the extent that this research on mice reflects the situation in humans, it has enormous implications for how much food we eat, our body fat, our heart and metabolic health, and ultimately the duration of our lives,” said Professor Simpson. “We have shown explicitly why it is that calories aren’t all the same. We need to look at where the calories come from and how they interact.”

Co-author Professor David Le Couteur added: “this represents an enormous leap in our understanding of the impact of diet quality and diet balance on food intake, health, ageing and longevity. We now face a new frontier in nutrition research.”

By examining mice fed a variety of 25 diets, the research team used an innovative state-space nutritional modelling method developed by Professors Simpson and Raubenheimer to measure the interactive effects of dietary energy, protein, fat and carbohydrate on food intake, cardiometabolic health and longevity.

The results suggest that lifespan could be extended in animals by manipulating the ratio of macronutrients in their diet – the first evidence that pharmacology could be used to extend lifespan in normal mammals.

Although mice were the subjects of this study, Le Couteur said the results from the study aligned with previous research in humans, but with a much larger number of dietary treatments and nutritional variables.

“Up until this point, most research has either concentrated on a single nutritional variable, such as fat, carbohydrate or calories, so much of our understanding of energy intake and diet balance is based on one-dimensional single nutrient assessments,” he said.

“The advice we are always given is to eat a healthy balanced diet, but what does that mean? We have some idea, but in relation to nutritional composition we don’t know terribly well. This research represents an important step in finding out.”

In terms of practical advice, the researchers predict that a diet with moderate amounts of high quality protein (15-20 per cent of total calorie intake) that is relatively low in fat and high in good quality complex carbohydrates will yield the best metabolic health and the longest life.