Reduced protein intake, through dilution with carbohydrate, extends lifespan and improves mid-life metabolic health, but with transition to highly processed diets, reduced dietary protein is associated with poor health outcomes in humans.

Low-protein (10%), high-carbohydrate (70%) diets promote the healthiest metabolic outcomes when carbohydrate contains resistant starch.

The type of carbohydrate and its digestibility profoundly shape the behavioural and physiological responses to protein dilution, modulate nutrient processing in the liver and alter the gut microbiota.