Animal studies may shed light on human obesity

Studies of other animals' feeding behaviour may help explain why humans are susceptible to obesity in the modern environment, internationally recognised nutritional ecologist Prof David Raubenheimer says.

In a lecture in Dunedin on Monday night Prof Raubenheimer, originally from South Africa and now at Massey University, said nutritional ecologists typically asked questions about why animals chose foods, what they did if they could not get the foods required and what the consequences of their choices were.

Despite a vast amount of research into these questions, they remained poorly answered for most animals.

The reason was nutrition was "deceptively complex".

To help address this he had been involved with the development of nutritional geometry, which used mathematical concepts to show how animals achieved the balance of carbohydrates/fats to protein.

While research is ongoing, including that involving several types of monkeys, chimpanzees, gorillas and humans, studies so far have shown some differences.

A study of mountain gorillas in Uganda showed their behaviour appeared to be different from humans and spider monkeys.

While humans who choose food rich in carbohydrate and fats overeat those foods to get sufficient protein, the gorillas appeared to do the opposite.

They prioritised non-protein energy and to do this, during the eight months of the year when their diet was restricted to protein-rich leaves, they ended up oversupplying themselves with protein in order to get sufficient fats and carbohydrates.

The amount of protein the gorillas were consuming in these circumstances was similar to that recommended on the high-protein human weight-loss Atkins diet.

During the other four months of the year, when they were eating a fruit-dominated diet, the amount of protein the gorillas took in was similar to that recommended for humans, about 15% of total food intake, or about half the Atkins diet level.

The research suggested an Atkins-type diet would "absolutely not" work on gorillas.

However, a similar study of spider monkeys showed their behaviour was similar to humans.

It was hoped the extensive study of other primates and more human studies would provide a "better handle" on what was driving the differences, he said.

There were a number of reasons the protein content of humans' diet had become diluted with fats and carbohydrates in recent years, including the relatively high price of protein.

Prof Raubenheimer has suggested craving for protein caused people to overeat low-protein food.

elspeth.mclean@odt.co.nz