The eating habits of Uganda gorillas could provide a clue as to why humans are becoming increasingly obese, according to a recent Massey University scientist's study.
Nutritional ecologist Professor David Raubenheimer, from the Institute of Natural Sciences, studied gorillas in remote Bwindi Impenetrable National Park, who seasonally over-ate protein to meet their needs for carbohydrates and fats.
But the results of the study surprised the researcher because they were opposite to what humans did, which was to over-eat carbohydrates and fats to get enough protein.
In the four months of the year when fruits were freely available, the rare apes ate a diet that provided 19 per cent of energy from protein. The study showed this was close to a balanced diet for gorillas and was similar to the protein requirements of humans.
But in the eight months of the year when fruits were scarce in their high-altitude forest habitats, the gorillas ate a diet containing 30 per cent protein.
"This provided us with a natural experiment in which we could test whether the appetite of mountain gorillas is more tightly linked to protein or non-protein energy [carbohydrates and fats]," Prof Raubenheimer said.
"If protein is more important, then gorillas stuck on the high protein diet will eat enough food to satisfy their need for protein, but in the process eat less than the required amount of fats and carbs."
The eating pattern explained a lot about the nutritional biology of our own species, he said.
"It means that our intake of fats and carbs, and hence of energy, is lower when we eat a diet high in protein -- which is how high protein weight loss diets, like the Atkins diet, work.
"But there is a flipside -- when we eat a diet low in protein, we over-eat fats and carbs to satisfy our appetite for protein."
This could explain the rise over the past few decades in human obesity, he said.
"For a number of reasons, including the relatively high price of protein, the protein content of our diets has over the past 50 years become diluted with fats and carbs. Our craving for protein causes us to over-eat the low-protein foods, in the same way that an alcoholic would drink more low-alcohol lager to satisfy his addiction."
The findings have been published in the British journal Biology Letters.