Labrador Retrievers tend to be more prone to obesity than other breeds.
In fact, Labrador Retriever owners consistently report to their veterinarians that their Labs are especially interested in food, more so than other kinds of dogs.
In an effort to decode the reasons behind higher obesity rates in Labs, veterinary surgeon and geneticist Eleanor Raffan, of the University of Cambridge, set out to discover whether or not there's a biological basis for excessive food-motivation and higher obesity rates in Labradors.
Raffan began the study with a group of 15 obese and 18 lean Labrador retrievers. The team honed in on three obesity-related genes to study (the genes they chose have all been shown to affect human weight).
The data collected from the dogs reveled some interesting information about a gene called POMC. More of the obese Labs carried a variation of POMC, where the DNA at the end of the gene was scrambled. Scientists believe this variation (a deletion) of POMC reduces a dog's ability to produce two specific neuropeptides that play a role in telling the brain that the body is no longer hungry after a meal.
Raffan and her team then sampled 310 more Labrador Retrievers. Their findings revealed a collection of symptoms associated with the POMC deletion. Although not all the dogs with the deletion were obese, and not all the obese dogs carried that variation of the gene, the overall findings revealed that the deletion was associated with a higher average bodyweight by two kilograms.
An accompanying survey of the dogs' owners supported the study's findings. Owners of the dogs with the POMC deletion reported that their dogs were more food-motivated, frequently begged for food, and were constantly on the hunt for scraps.
The team then sampled another 411 dogs from both the U.S. and the U.K. This time, the sample population included multiple breeds. The researchers discovered that the POMC deletion occurs in about 23% of Labrador retrievers overall. Furthermore, of the 38 other breeds included in the study, the POMC deletion showed up only in Flat Coat Retrievers (related to Labrador Retrievers) and produced the same food-obsessed behaviors and higher average bodyweights as recorded in the previous studies.
"We've found something in about a quarter of pet Labradors that fits with a hardwired biological reason for the food-obsessed behavior reported by owners...There are plenty of food-motivated dogs in the cohort who don't have the mutation, but there's still quite a striking effect," Raffan says of the study's findings.
Interestingly, the researchers noted that the POMC mutation was far more common in the 81 service dogs (all Labs) included in the study. Seventy-six percent of these dogs carried the deletion.
"It's possible that these dogs are more food-motivated and therefore more likely to be selected for assistance-dog breeding programs, which historically train using food rewards," says Raffan.
However, she is quick to add that not enough data yet exists to confirm this hypothesis.
"We haven't yet looked at puppies and asked if they're more likely to qualify as an assistance dog if they have the mutation."
Raffan and her team are working on applying their canine obesity findings to studies of obesity in humans. Historically, researchers have used mice and rats to study POMC mutations. In rodents, the gene is too different from the human version for any findings to be immediately meaningful. However, researching canine obesity could very well help scientists advance their understanding of the disease in humans.
The study was published in the journal Cell Metabolism and you can check it out here.
Do you have a Lab? Does he seem more interested in food than other dogs? Tell us in the comments below.
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