In order to study the effects of PYY, the researchers genetically engineered mice that were unable to produce the "gut hormone." The genetically engineered mice ate more than regular mice and became obese even when they ate high-protein foods. The engineered mice were then treated with PYY and showed decreased weight and food consumption. When the PYY treatment was discontinued, the improvements ceased and reversed.
"We have proved that if you do not have PYY you become obese, and if you give it back then you lose the weight again," said researcher Dr. Rachel Batterham. She added that, while the diet change could be as simple as 2 to 3 percent increases in protein and small reductions in carbohydrates such as potatoes, "It's not a diet that you would go on for a few months. You would go on it for life."
Battterham said she suspects the explanation for PYY's effects is evolutionary -- protein made up a large part of hunter-gatherer diets -- and noted the next step was to perform long-term human trials.
"We need to check that it would be compatible with lifestyle and look at the safety aspect," she said.
Rachel Cooke of the British Dietetics Association agreed.
"More research is certainly needed on this type of dietary regimen before firm recommendations can be made about its long-term safety and efficacy," she said.
"Many natural appetite suppressants actually work by promoting PYY production," explained Mike Adams, coauthor of Natural Appetite Suppressants for Safe, Effective Weight Loss. "Injecting the PYY hormone is not the only way to control hunger. Various eating patterns, food choice and supplements can also greatly impact the production of this hormone and thereby help regulate appetite."
###