Why Labradors dogs are always hungry according to science?

A work in Cell Metabolism identifies the first canine obesity gene.
Research explains why Labradors are unable to satiate themselves.

In addition to being peaceful and calm, Labrador retrievers are known to be always hungry. This has been one of the most famous anecdotes among veterinarians, who come to describe Labrador retrievers as “vacuum cleaners” due to their ability to ingest food. The breed, from the island of Newfoundland (present-day Canada), is one of the most popular in the world.
Labradors are also known as “vacuum cleaners” for their inability to satiate
A study published in the journal Cell Metabolism reveals the first biological explanation for why Labradors are always hungry. The research, led by scientists from the University of Cambridge, has identified the first gene linked to canine obesity. Variants of this DNA sequence, related to an increased appetite, have been discovered in Labrador retrievers. Coincidentally, these gene variations have also been observed more frequently in those specimens used as guide dogs, which are usually educated using food as a reward.

First gene for canine obesity
“When something is more common in one breed than another, we always think that genetics may play a role,” says Eleanor Raffan, a veterinary surgeon and geneticist at the University of Cambridge, who had previously studied obesity in humans. When approaching the study of Labrador retrievers, the scientists looked at three different genes related to being overweight in our species. This is how they determined that the POMC gene could have relevance in the behavior of this breed.

Deletion of the POMC gene prevents dogs from producing neuropeptides with which they would stop being hungry
While in humans this genetic sequence has been associated with differences in body weight, scientists have found that mutations in the POMC gene cause increased appetite in Labradors. In particular, the removal of fourteen base pairs from the end of this gene prevents dogs from producing the neuropeptides β-MSH and β-endorphin. Both molecules are responsible for ending the feeling of hunger once we have eaten. By not producing these compounds, the Labradors are never satisfied.

The research, which included the analysis of 310 Labrador retrievers, determined that this genetic variant is associated with an increased appetite. The deletion or elimination of the gene was also related to a weight gain of 2 kilograms in the specimens studied. Those with this genetic mutation appeared to be more motivated by food. According to a later study, which examined Labrador retrievers from the United States and the United Kingdom, 23% of the animals had the genetic variant associated with obesity.
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The study provides more information on the causes behind being overweight. In addition to identifying the first gene for canine obesity, the scientists were surprised to see that Labrador-type guide dogs more often had the mutation in the POMC gene. This variant would explain why this type of specimen is easier to train and educate using food as a reward, although scientists prefer to be cautious given the small number of dogs analyzed.
Understanding canine obesity can provide new clues about overweight in the human species

In developed countries, between 34 and 59% of dogs are obese, a problem that is related to a shorter life expectancy, diabetes, cardiovascular disease, cancer and, in general, higher morbidity. The results presented, therefore, not only explain why Labradors are always hungry, but they can improve the care of all animals, explaining the causes behind their overweight. In addition, according to the researchers, understanding canine obesity can also help us better understand this public health problem in our own species