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Even for dogs, Labrador retrievers are gluttons. This scientist can explain why.

Just look at Sampson — who in 2011 was reported to maybe be the fattest lab in Australia. At 187 pounds, he was heavier than the average human male, and suffered from high blood pressure according to vets, which makes it hard for him to go for walks.
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We need to talk about Labrador retriever obesity, the world's cuddliest epidemic.

According to the Association for Pet Obesity Prevention, around 54 percent of all dogs in the US are overweight or obese. But Labs top the scales. According to a survey of veterinarians, around 60 percent of Labs they see are obese.

While some pet owners may argue there's just "more to love," these overweight dogs suffer health consequences. Heavy dogs have a lower life expectancy and higher risks for heart disease, bone problems, and cancer.

All dogs love food. But it seems Labs love food more than most, and it may be linked to their genes.

"[Labradors] are not only the most commonly overweight breed of dog, but they are notorious for being obsessed by food," Eleanor Raffan, a veterinarian and metabolic researcher at the University of Cambridge, tells me. "Some particularly badly [obsessed] dogs will eat things no other creature would want to consume."

This is a mystery worthy of scientific study: Why might Labs be cursed with ravenous hunger?

Labs' gluttony may be linked to a genetic mutation

"Plodding along with its giant belly this obese dog is more than twice its ideal bodyweight. Alfie, the podgy pooch, was a whopping [168 pounds] when he was rescued by the RSCPA." — I didn't write this caption. It is amazing.
Barcroft Media /Barcoft Media via Getty Images

In recent years, scientists have identified a few genes in rats and other mammals that may be responsible for sending appetite into a frenzy.

One of them is a gene that codes for a chemical called POMC (proopiomelanocortin). "It's normally part of a switch that turns off hunger," Raffan says. "If you're not producing it — if you've got a scrambled copy of the gene — it won't work."

POMC works in the hypothalamus, an evolutionarily ancient part of the brain that controls many of our unconscious processes: thirst, sex drive, body temperature, etc. Changes in this part of the brain affect individuals in subtle, powerful ways. It could be what's prompting the dogs to be extra motivated to scavenge for food.

Scientists know that humans who have trouble producing POMC also tend to have weight issues starting very early in life. And when the genes for POMC are knocked out in mice, they become obese.

So the genes for POMC in Labradors were a natural place for Raffan and her colleagues to look for a biological explanation for the dogs' prevalent obesity. (They also searched for a few other known genetic links to appetite, but POMC quickly became the prime candidate.)

They recruited a group of 310 labs in the UK. Some were pets; others were service dogs.

Raffan and her colleagues found that a mutation in the POMC gene — specifically a deletion of 14 base pairs — was highly significantly associated with heavier dogs. (The P-value was .0001. Usually smaller than .05 is considered significant.)

The dogs with mutation also scored higher on tests of their motivation to eat food.

How could you not feed this face?
Thomas Hawk / Flickr

Raffan says the results strongly suggest that in dogs with the mutation, the genetic pathway to turn off hunger is broken. And dogs with multiple copies of the mutation were even more likely to be fat. "One copy of the mutation, you're a bit hungrier," Raffan says. "If you have two copies, it's another step up. It's an almost linear response. It's quite striking."

The researchers tested dozens of other dog breeds and could only find one — the flat-coated retriever, a cousin of the Lab — that also has the POMC mutation. Flat-coated retrievers with the trait were also huskier, and were similarly motivated to eat with gleeful abandon.

"It's amazing that this one simple change that acts in the unconscious part of the brain can then have these complex manifestations," Raffan says. Just one mutation can influence how much a dog scavenges for food, for instance.

Lab owners concur with the Labs' strong scavenging instinct. In 2014, redditor Dtomb asked fellow Lab owners to name "the strangest/most random thing" their dogs had eaten.

Answers included:

  • Lawn mower clippings
  • A plastic baby Jesus
  • A whole bar of soap
  • Weather stripping (yum!)

It's not all bad for these ultra-hungry dogs

Interestingly, the service dogs in Raffan's study were more like to have the mutation, which suggests that the trait also make the animals more trainable. "If you’re more hungry, you’re perhaps more willing to work for your treat," Raffan says.

The study also suggests that as humans selected obedient dogs for breeding, we also selected hungrier ones.

This research may also give scientists a window into how POMC regulates appetite in humans. That's because a lot of the POMC research occurs in rodents, but dogs' genetic code is more similar to our own. In humans, researchers suspect POMC may also play a role in hunger regulation, but it's currently unclear if it can be leveraged to combat the obesity epidemic.

Dog owner Becky Jones pets 4-year-old Labrador Chubby Charlie in Northfield Birmingham, United Kingdom, October 24, 2001.
Mike Thomas/Express Newspapers/Getty Images

What's a pet owner to do?

We may be getting a better understanding of the genetics of hungry dogs, but we still have to face the trend in dog obesity. Dogs across the board are growing fatter, whether or not they have a mutation.

A lot of this is fueled by owners feeding their dogs too much — in particular too much human food. But dogs can also be sneakily manipulative when they're super hungry. "There is evidence to suggest dogs are able to influence both the type and quantity of food offered to them by their owners," Raffan's paper says.

Keeping a dog slim is tough when they're so damn adorable when they beg. For dogs, food is love. And when we feed them we're showing them love.

But it's crucial for dog heath to only feed them the amount of food a veterinarian recommends, even though they beg for more. It may be an even greater act of love to deny them. They'll live longer, healthier lives.

"If you have a dog with this mutation, it's going to be an awful lot harder work to keep them slim," Raffan says. "If you do it, you should give yourself a big pat on the back."