By Andrea Hargraves 
The mutation is found in one in four Labrador retrievers and two in three flat-leaf retrievers.
- author, Helen Briggs
- scroll, Environment correspondent
Scientists say a genetic mutation makes some Labrador retrievers and flat-leaf retrievers feel constantly hungry but burn fewer calories.
This “double effect” means that owners of these dogs must pay special attention to keeping their pets slim.
The mutation is found in one in four Labrador retrievers and two-thirds of flat-faced retrievers.
“This shows us the power of our genes to change how we feel about food,” says the study's lead scientist.
Dr. Eleanor Ravan, from the University of Cambridge, says that dogs, like humans, have genes that affect interest in food and metabolic rate.
She told the BBC: “If we get the genes that make us feel hungry or want to eat, it takes more effort to stay fit.”
Dogs with the genetic mutation are not only hungrier between meals, but also expend 25% less energy while resting.
The study builds on previous research on a mutation in the gene known as POMC.
The POMC gene and the brain pathway it affects are similar in dogs and humans.
Dogs with this mutation are not only hungrier between meals, but they also use about 25% less energy when they are resting, meaning they do not need to consume as many calories.
“Dogs with this genetic mutation experience a dual effect: not only do they want to eat more food, but they also need fewer calories because they don’t burn them as quickly,” says Eleanor.
More than 80 Labrador retrievers participated in the study.
They were put through several tests, including a “sausage in a box” test, where they were lured with a hidden free gift that they could see and smell.
Dogs with the POMC mutation reached for hot dogs much more than dogs without them, indicating greater hunger.
Flat-furred dogs were allowed to sleep in a special chamber to measure the gas they exhaled, revealing that those with the POMC mutation burned approximately 25% fewer calories than dogs without it.
Katherine Taylor has a “big black lab” named Leo who participated in the study.
She said he will eat anything, even a salad bowl from the table, green beans from small gardens, and he has been known to pick carrots.
“You can feed him and he will still want more food,” he said, adding that they struggle to keep him lean, including using a slow feeder.
About two in three dogs (34-59%) from wealthy countries are overweight.
Labradors have the highest levels of obesity and have been shown to be more obsessed with food than other breeds.
They make great pets and working dogs because they are relatively easy to train.
We may have subconsciously chosen Labradors with the mutation because they love food and will do anything for a cookie.
The research, published in the journal Science Advances, was funded by the Wellcome Trust and the Dogs Trust.