LONDON — If you’ve ever had a Labrador retriever, you know about one of the breed’s notable traits: an unrelenting appetite. The dogs will devour anything from socks to rocks, and given the chance, they can be prone to eat themselves into obesity — by one estimate, nearly 60 percent of all Labradors are overweight or obese.
In fact, the dubious honor of being named Britain’s fattest pet went to a 176-pound Labrador named Alfie, who was rather uncharitably described by one official as “a massive blob with a leg at each corner.”
Labradors have been caught sitting under an apple tree waiting for the fruit to fall, and dragging their owners to a spot in the grass where they once found a discarded kebab years before.
Is it a character flaw? Are they incorrigible gluttons? Scientists at Cambridge University say no: Labradors can’t help it; it’s in their genes.
Researchers studying 310 Labradors found that many of them were missing all or part of a gene known as POMC, which is known to regulate appetite in some species and to help sense how much fat the body has stored. Without it, the dogs don’t know when they’ve had enough, so they just keep eating and eating.
The POMC gene is also present in humans, and while cases are very rare, there are obese people with a similar gene deficiency.
The Labrador study “reminds people that hard-wired biology explains why some animals, like affected Labradors and indeed some humans, are more prone to obesity than others,” said Eleanor Raffan, the lead researcher. “Their genes mean they are more hungry all the time.”
Scientists have found the POMC mutation to be widespread in only one other dog breed: flat-coated retrievers, which are cousins to Labradors. Ms. Raffan said the scrambled POMC gene partly explains why Labradors are especially easy to train as service dogs: “They will be willing to work harder” for a treat, she said.
The scientists think the gene mutation arose in an earlier breed that Labradors are descended from, the St. John’s water dog, which fishermen used to retrieve nets in the icy waters of Newfoundland. “The tendency to eat every food that’s thrown your way would have been sensible” under those conditions, Ms. Raffan said, but for a modern Labrador living a cushy life as a pet, the mutation is no longer beneficial.
Canine obesity is on the rise generally, but for most dogs, rich food and lack of exercise are to blame, not genes.
Poor Alfie’s owner apparently kept forgetting that he had already been fed, and the dog eagerly ate one extra meal after another. He grew so fat that it took four people to lift him, using towels as slings. Bone damage and breathing problems prompted a crash diet, but to no avail: Alfie eventually had to be euthanized.