Chickens Overeat Because They Can’t Tell They’re Full

Why do chickens overeat? Some varieties keep stuffing themselves until they’re so fat that they can’t even mate. Hey, it might seem funny to you, but it’s probably no joke to the plump poultry. A new study from researchers at The Roslin Institute at the University of Edinburgh may have the answer.

Ian Dunn, lead author of a paper on the findings which were recently published in the American Journal of Physiology, Endocrinology and Metabolism, said that farmers have known for a long time that faster-growing chickens “are more insensitive to feelings of fullness than others.”

They looked at a peptide called cholecystokinin (CCK), which is a protein that’s also found in other animals including humans. One of its tasks is to signal the brain when the body has taken in enough food.

It’s safe to say that for some people — and some chickens — CCK has fallen down on the job. Even our pets have fallen prey to the obesity epidemic.

The new study confirmed that bigger varieties of chickens had brains that didn’t get the memo from CCK when they’d had enough. Those birds kept eating. And eating.

And, as you might expect, the chickens that overate were the same chickens that ended up growing faster and getting fatter.

The researchers suspect that when the birds were first domesticated for food thousands of years ago, they were intentionally bred for bigger size — and, along the way, accidentally bred for the ability to overeat.

While we’re on the topic, what’s the biggest chicken breed out there? According to the National Jersey Giant Club, the biggest purebreed chicken is called, appropriately enough, the Giant. They can weigh as much as 15 pounds — enough to give a turkey a run for its money.

Speaking of chickens and overeating, I think I’m getting hungry.

[booted bantam chickens in the Netherlands image courtesy Wikipedia Commons]