Researchers at the University of Sydney say that high-protein diets may work better than calorie counting for weight loss.
Nutritional values of foods are typically given in kilojoules or kilocalories, standard units of energy. However, new research on apes and monkeys suggests that this is too simplistic as different macronutrients - carbohydrates, fats and proteins - interact to regulate appetite and energy intake.
In these animals, overall energy intake seems to be less important than achieving the correct nutritional balance.
"Foods are complex mixtures of nutrients and these do not act independently but interact with one another. The appetite systems for different nutrients compete in their influence on feeding," said Professor David Raubenheimer, a nutritional ecologist, at the University of Sydney.
When foods are nutritionally balanced, there is no competition between these appetite systems, and when one nutrient requirement is satisfied, so too are the others. Many foods however, are unbalanced and have a higher or lower proportion of protein to carbohydrate than the animal requires.
Therefore, to obtain the right amount of protein the animal may have to over- or under-eat fats and carbohydrates. The researchers studied baboons that live on the edge of human settlements. Despite eating different combinations of foods each day, they achieved a consistent balance where 20 per cent of their energy needs came from protein. However, their overall energy intake varied significantly, over a five-fold range.
"This suggests that the baboon values getting the right balance of nutrients over energy intake per se," said Raubenheimer.
Other studies found that spider monkeys and orangutans, too, foraged for a balanced diet. But when seasonal availability of some foods prevented them from getting a balanced diet, they prioritised getting the right amount of protein even if this meant eating too much or too little fats and carbs.
Like spider monkeys and orangutans, humans prioritise protein over carbohydrates and fat. This means that if we have a diet with low protein, we will over-eat fats, carbs and energy to get the target level of protein. "We can use this information to help manage and prevent obesity, through ensuring that the diets we eat have a sufficient level of protein to satisfy our appetite," Raubenheimer said.