Science Explains Why Your Lab Is Always Hungry

Dogs love food. Some love it more than others, and some of those are Labrador retrievers—the bottomless pits of the canine world. Scientists announced today that they’ve found a gene variant in labs that may explain that constant state of "Please Feed Me." The findings were published last year in the journal Cell Metabolism.

Dog obesity isn't something we talk about a lot, but there sure is a lot of it. In the U.S. and other wealthy countries, between 34 and 59 percent of dogs are overweight. And yes, fat dogs are cute, but they’re also in danger of some serious health problems. Canine obesity can cause heart disease, strain on a dog’s joints, diabetes, and can even shorten a dog’s lifespan.

Some breeds, like black labs, chocolate labs, and golden retrievers, are more obesity-prone than others. This is likely because, like many of us, they are highly motivated by food. Labs’ human companions learn quickly that a treat is the trick to getting their dog to behave. But those treats add up.

The domesticated dog, Canis familiaris, is a single species with a lot of variations. Great Danes and Chihuahuas are both dogs, but their bloodlines, and therefore their genes, are dramatically different. And all those differences within a single species make dog breeds a great resource for scientists studying genetics.

Researchers recruited nearly 400 adult Labrador participants. Of those dogs, 310 were pets recruited through an email invitation from the UK Kennel Club, and 80 were part of an assistance-dog breeding colony. Some of the dogs were fat, while others were not, but all of them were healthy, with no pre-existing conditions.

First, the dogs were weighed. Then the scientists collected drool samples from 33 of the dogs and sequenced the DNA within. The dogs’ owners then completed a survey about their labs’ eating habits.

As relatives, of course, the labs had a great deal of genetic material in common with each other and with other dog breeds. But they also had one gene variant that stood out: the deletion of 14 base pairs from a gene called pro-opiomelanocortin, or POMC. Previous studies of this POMC variant have shown a relationship with appetite and a feeling of fullness.

Each dog could have one copy of the POMC variant, two copies, or none. The more copies a dog had, the fatter and more food-motivated it was. And about 23 percent of labs are carrying at least one copy of the variant.

"People who live with Labradors often say they are obsessed by food, and that would fit with what we know about this genetic change," Cambridge University metabolism expert and lead author Eleanor Raffan said in a press statement.

Her co-author, Stephen O’Rahilly of the Wellcome Trust-Medical Research Council Institute of Science, says these findings have implications beyond kibble. "Common genetic variants affecting the POMC gene are associated with human body weight and there are even some rare obese people who lack a very similar part of the POMC gene to the one that is missing in the dogs. So further research in these obese Labradors may not only help the well-being of companion animals but also have important lessons for human health."