ANIMALS are hard-wired to seek out their ideal nutritional balance and protein is key to this equation, a meeting of Hunter nutritionists heard yesterday.
University of Sydney Professor Steve Simpson presented one of the first in a series of seminars at Hunter Medical Research Institute.
The former Oxford biologist has studied locusts, cockroaches, ants, mice and even the Mormon cricket.
He found when animals were allowed to eat whatever they wanted, they naturally selected the nutrients that worked together to meet their optimum dietary requirements.
However, when environmental factors changed, such as a shortage of protein, the animals compensated by eating more units of kilojoule-laden carbohydrates in even greater amounts than they were deficient in protein.
This led to obesity.
"We started to look at out herbivores and omnivores and found the same pattern," Professor Simpson said.
"But not in predators."
In human experiments, researchers found that, as protein was taken out of subjects' diets, they compensated by eating more savoury snacks between meals.
"The fat and the carbs were producing a protein decoy," Professor Simpson said.
"That's what potato chips and that's what hot chips are."
Professor Simpson said this was why high-protein diets worked because they flipped the equation around and people lost weight.
"People eat less because they've got their protein requirement at a low total energy intake."
Among his examples was the Mormon cricket bands in Utah that migrated en masse, which his team proved was motivated by a search for protein.
If that protein could not be found, the insects would eat their kin - cannibalism of the insect world.
However, Professor Simpson warned against too much protein.
"Protein is needed for growth and reproduction but too much shortens life span or impairs reproduction, so balance is needed," Professor Simpson said.
His studies have showed that, when given the choice, animals naturally eat in a way that ensures the best reproductive outcomes, not the longest life span.