When it comes to greedy canines, labradors take the biscuit. Now researchers have shed light on why the breed is prone to a portly form.
Scientists previously revealed a mutation in a gene called POMC (proopiomelanocortin) predisposes dogs to obesity. The genetic variant is found in about a quarter of labrador retrievers and two-thirds of flat-coated retrievers, with the effect slightly larger in the former.
Now two explanations have emerged for the association: not only are dogs with the mutation hungrier between meals, but they burn fewer calories when at rest.
“It means that these dogs have a double whammy,” said Dr Eleanor Raffan, of the University of Cambridge, who led the study.
But canine obesity is not a fait accompli.
“What we know is that there [are] loads of owners who manage their dogs really carefully, and do manage to keep them slim – but they do it by putting a lot of effort in,” Raffan said.
Writing in the journal Science Advances, Raffan and colleagues describe how their first test involved 36 adult labradors that carried either one copy of the POMC mutation, two copies, or did not have the mutation at all.
The dogs, which were all on a standard diet, were given breakfast and three hours later shown a transparent box with a perforated lid into which a researcher placed a sausage. The dogs were then allowed to approach the box.
The researchers found dogs with the POMC mutation spent far less time resting or exploring the room, and more time attempting to get at the morsel, than those without.
“The dogs with the mutation were just much more fixated on the sausage,” said Raffan, adding that it suggested they were hungrier.
However, a subsequent test with 24 labradors with either one or no copies of the mutation highlighted this was not because they felt less full straight after eating: regardless of their genetics, the dogs voluntarily consumed a similarly enormous quantity of wet dog food – about 2kg on average – when offered a can every 20 minutes.
The team also analysed the calories burned by 19 adult flat-coated retrievers when at rest by measuring their oxygen consumption and carbon dioxide production in a specially modified kennel.
The results revealed dogs with two copies of the mutation burned about 25% fewer calories than those with no copies – enough, the researchers say, to significantly decrease how much food they required to maintain healthy body weight.
While the situation is more complex in humans, Raffan said the study was a powerful illustration of how genes could influence behaviour around food.
“It’s a message about the fact that obesity isn’t a choice,” she said. “It’s a reflection of a background drive to eat, which is driven by a combination of your genes and your environment.”
