Why are so many Labradors fat?

Like owner, like dog? Almost two-thirds of dogs in developed countries are overweight, with Labradors having the highest rate of canine obesity. Now we know the secret to their insatiable appetite: mutations in a gene that has been linked to hunger in humans.

Conor O’Donovan at the University of Cambridge and his colleagues found the genetic variant by studying 310 Labrador retrievers, assessing both their weight and their desire for food.

They found that 23 per cent of the dogs carried at least one copy of a mutant form of a gene called POMC, which encodes proteins that help switch off hunger after a meal. For each copy of the mutant gene, a dog was on average 1.9 kilograms heavier than Labradors with no copies of the variant.

Problems with POMC also affect humans. Babies with compromised POMC function are constantly hungry, and become obese at a very early age.

But research into this gene’s role in obesity has been hindered by the fact that the version of it that rats and mice have is very different from ours. The latest study shows that POMC in Labradors is more similar to ours, meaning these dogs may help us to better understand the importance of this gene in human weight gain.

Fitter puppies

The retrievers’ genetic affliction could be our fault. The team found that the mutant form is particularly common in Labradors that have been bred as assistance dogs, for example to guide people with sight problems. Because food is often used as a reward during training, we may have been inadvertently selecting and breeding Labradors that have this gene variant, which makes them especially interested in food.

“Food is often used as a reward during training, and carrying this variant may make dogs more motivated to work for a titbit,” says Giles Yeo at the University of Cambridge, who also worked on the study.

Now that the gene variant has been discovered, it opens the possibility to breeding the mutation out of Labradors, to produce leaner dogs, says O’Donovan. “I think it’s reasonable to predict people will control dog breeding to improve the health of future dog generations.”

Journal reference: Cell Metabolism, DOI: 10.1016/j.cmet.2016.04.012

Read more: We must breed happier, healthier dogs