The science behind chubby Labradors

You can officially blame genetics for your tubby puppy (Getty)
You can officially blame genetics for your tubby puppy (Getty)

They're loyal, hard-working, great with children -- and also tend to be a bit on the tubby side.

Labrador retrievers often have a bit of a weight problem but the latest scientific research finds it's not entirely their fault.

Instead, it's a distortion in a gene called POMC that is to blame. It is suspected the variation in the gene prevents the dogs from being able to recognise they're no longer hungry at the end of a meal.

A sample of 310 Labrador retrievers found the dogs with the DNA variation were more likely to be overweight -- on average, it was linked to a 2kg weight gain -- and were more food-motivated, according to the owners.

It means the weakness can also be a strength -- food is frequently used as a reward in training and it motivates these dogs more.

"We've found something in about a quarter of pet Labradors that fits with a hardwired biological reason for the food-obsessed behaviour reported by owners," says Eleanor Raffan, a veterinary surgeon and geneticist at the University of Cambridge.

"There are plenty of food-motivated dogs in the cohort who don't have the mutation, but there's still quite a striking effect."

The work they put in is well received, with Labrador retrievers commonly trained and used as assistance dogs.

And the DNA variation was even more noticeable in those well-trained pooches. In the study's sample of 81 assistance dogs, 76 percent had the gene difference.

Even though your pup may not have genetics on its side, owners still need to work at keeping their dogs at a healthy weight, Dr Raffan says.

"You can keep a dog with this mutation slim, but you have to be a lot more on-the-ball -- you have to be more rigorous about portion control, and you have to be more resistant to your dog giving you the big brown eyes.

"If you keep a really food-motivated Labrador slim, you should give yourself a pat on the back, because it's much harder for you than it is for someone with a less food-motivated dog."