JOIN USScientists have identified a genetic variation associated with obesity and appetite in Labrador retrievers, a finding that may explain why they are more likely to become obese than dogs of other breeds.
In developed countries, between one and two in three dogs (34-59 per cent) is overweight, a condition associated with reduced lifespan, mobility problems, diabetes, cancer and heart disease, as it is in humans, researchers said.
The increase in levels of obesity in dogs mirrors that in humans, implicating factors such as reduced exercise and ready access to high calorie food factors, they said.
However, despite the fact that dog owners control their pets' diet and exercise, some breeds of dogs are more susceptible to obesity than others, suggesting the influence of genetic factors.
Researchers at University of Cambridge studied 310 pet and assistance dog Labradors.
Veterinary professionals weighed the dogs and assessed their body condition score, and the scientists searched for variants of three candidate obesity-related genes.
The team also assessed 'food motivation' using a questionnaire in which owners reported their dog's behaviour related to food.
The researchers found that a variant of one gene known as POMC, was strongly associated with weight, obesity and appetite in Labradors and flat coat retrievers.
Around one in four (23 per cent) Labradors are thought to carry at least one copy of the variant. In both breeds, for each copy of the gene carried, the dog was on average 1.9 kg heavier.
"This is a common genetic variant in Labradors and has a significant effect on those dogs that carry it, so it is likely that this helps explain why Labradors are more prone to being overweight in comparison to other breeds," said Eleanor Raffan from the University of Cambridge.
The gene affected is known to be important in regulating how the brain recognises hunger and the feeling of being full after a meal.
"Labradors make particularly successful working and pet dogs because they are loyal, intelligent and eager to please, but importantly, they are also relatively easy to train," said Giles Yeo, from University of Cambridge.
"Food is often used as a reward during training, and carrying this variant may make dogs more motivated to work for a titbit," Yeo said.
"But it's a double-edged sword - carrying the variant may make them more trainable, but it also makes them susceptible to obesity," he said.
The researchers believe that a better understanding of the mechanisms behind the POMC gene, which is also found in humans, might have implications for the health of both Labradors and humans.
The research was published in the journal Cell Metabolism.