Health · Nutrition · Science · Veterinary Care

Do These Genes Make Me Look Fat?

The Labs have a problem.

Actually, some Labs have a problem.

It’s in their genes: In 2016, a group of researchers at the University of Cambridge discovered a genetic anomaly in a small group of overweight Labrador Retrievers (1). Specifically, the modification is a short deletion sequence in a gene called POMC. The presence of this deletion was found to be positively associated with an increased tendency towards both the tendency to overeat and an increase risk of obesity. Technically then, because the problem is a deletion issue, this is not so much an “obesity gene” as it is the lack of a body weight control gene. The former description is more catchy, but less accurate.

In the study, the researchers examined all possible genetic sequences that were candidates for being an “obesity gene.” The POMC deletion was found in 10 out of 15 overweight dogs and in only 2 our of 18 lean dogs.  Moreover, the investigators tested dogs from 39 other breeds and did not find the mutation. The only other breed that was found to carry the gene deletion sequence was the Flat Coated Retriever (FCR). Although FCRs are not typically associated with obesity, when the researchers tested 200 dogs, they found that, just as in Labradors, the mutant POMC gene was positively associated with higher body weight and greater food motivation.

SOME OF US ALSO CARRY THE FAT GENE…… WHO KNEW?

Confirming evidence: As we always like to see with good science, these results were subsequently corroborated by a separate and unrelated team of researchers (2). Like the earlier work, they found the mutation only in Labs and not in other breeds. One difference was that their results suggested that the POMC deletion variant may be inherited as a simple recessive gene rather than as having an additive effect, as suggested by the researchers in the initial study.

So, some (not all) Labs carry a fat gene that makes them more susceptible to obese conditions and to being highly motivated to overeat. Interesting information and, probably quite helpful for those Lab owners who have a tough time keeping their happy and energetic (and food-loving) Labrador Retriever from packing on the pounds.

But wait – there’s more! This year, overweight Labrador Retrievers once again became the focus of study (3). However, in this study, rather than focusing on the presence of a gene mutation, these researchers were interested in studying the flexibility of fat versus lean Labs.

No, not this kind. METABOLIC flexibility.

What is metabolic flexibility? Metabolic flexibility refers to the ability of cells in the body (their mitochondria, actually) to shift back and forth between using glucose and fatty acids for fuel. In healthy animals, including those of the human variety, this shift occurs after eating and is orchestrated in part by the response to the hormone insulin. Overweight conditions are associated with a reduced ability to make this shift – hence – “metabolic inflexibility.” In humans, this change is associated with several of the pathological changes of overweight conditions, such as abnormal blood lipid (fat) profiles, insulin-resistance, and diabetes.

Carnitine may also be involved. Carnitine is a nutrient that can be obtained through the diet, but is also produced by the body. It is necessary for the transport of long-chain fatty acids into a cell’s mitochondria so that they can be used as an energy source. Because of its role in fat metabolism, it has been theorized that carnitine status may be involved both in the metabolic changes associated with obesity and more specifically, with metabolic inflexibility.

CARNITINE

So: “What about overweight Labs? Do they show metabolic inflexibility and/or reduced carnitine levels? If so, are these changes related to the “fat gene” found in this breed?

A recently published study examines this question (3):

The Study: The researchers recruited 28 adult Labrador Retrievers living in homes. Of the 28 dogs, 16 dogs were overweight and 12 dogs were lean. Following an overnight fast, the dogs were fed a  high-fat meal that was composed of 50 percent of their estimated daily caloric requirement. Blood samples were taken before feeding (fasted) and hourly for a 4-hour period after the meal. Results: A group of several carnitine and phospholipid (fat) blood metabolites were measured. Fasting and postprandial measures of carnitine and acetylcarnitine were significantly lower in the overweight dogs when compared with lean dogs. Additionally, acetylcarnitine levels in lean dogs decreased in the first hour following consumption of a meal but this change was not observed in the overweight dogs. In those dogs, acetylcarnitine levels remained stable both before and after eating.

Conclusions: These results suggest that the overweight Labs in this study were experiencing a form of “metabolic inflexibility.” It was theorized that low carnitine status was slowing fatty acid oxidation (use) following a meal. While the authors suggested that  the overweight dogs were experiencing carnitine insufficiency, the design of the study did not allow determination of whether the low carnitine levels were a cause versus a consequence of overweight conditions. Regardless, these results do suggest a possible role of carnitine status in overweight conditions in dogs.

Take Away for Dog Folks: So, how does this information help the average dog and owner? First, it provides new information regarding metabolic changes that may be taking place in dogs who are overweight (Labs, anyway). These include changes in the dog’s ability to use fat as a fuel source and alterations in the body’s carnitine status.

Oddly, this new paper neither mentioned nor referenced the earlier work regarding identification of the POMC deletion and its connection to overweight conditions in Labrador Retrievers. My personal take-away from these two studies was to wonder if there exist differences in carnitine status and components of metabolic inflexibility between Labs who have the POMC deletion and those who do not. While the results of this new study are helpful in furthering our understanding of metabolic changes in overweight dogs, they also suggest a need to study possible connections with the POMC deletion sequence in the Labs who are unfortunate enough to be born without it.

Feed smart and exercise: The bottom line? Feed a high-quality food, provide your dog (all dogs, not just fat-prone Labs!) with plenty of enjoyable and stimulating exercise, and feed your dog a correct amount of food to achieve a lean and well-muscled body condition.

For those of you with a voracious Lab, remember, that part of his or her appetite could be in his genes……they may indeed be making him look fat.

I MAY BE CRAZY, BUT I AM LEAN AND FIT, CRAZY!

Cited Studies:

  1. Raffan E, Dennis RJ, O’Donovan, et al. A deletion in the canine POMC gene is associated with weight and appetite in obesity-prone Labrador Retriever dogs. Cell Metabolism 2016; 23:893-900.
  2. Mankowska M, Krzeminska P, Graczyk M, Switonski M. Confirmation that a deletion in the POMC gene is associated with body weight of Labrador Retriever dogs. Research in Veterinary Science 2017; 112:116-118.
  3. Soder J, Wernersson S, Dicksved J, et al. Indication of metabolic inflexibility to food intake in spontaneously overweight Labrador Retriever dogs. BMC Veterinary Research 2019;15:96-107.

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10 thoughts on “Do These Genes Make Me Look Fat?

  1. Thanks Linda! I really need to go bigger on the high value treats. I tend to get in a rush or have mittens on and get out of the habit of really doing the mindful training as I walk. I just need to get more focused and really target this issue! I walk with 2 dogs and that’s another issue! I do use harnesses and originally had tried the gentle leader, with Padfoot never really getting used to it, so switched, but maybe I should try that again.
    thanks again! I really enjoy your blog! Kathleen

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  2. I’ve owned a lot of Labs…I used to be a breeder. I’m grateful that the geneticists have provided substance for the hypothesis that there’s a genetic basis for the propensity to gluttony. My secondary hypothesis for this is that what we see in Labs is similar to what we see in marine mammals. Packing on blubber is a useful thing to do if your work involves a lot of swimming in the Bay of Fundy and you need to survive a long cold winter in the far North…as was the lot of the Lab’s ancestor, lesser St John’s dog.
    It would be interesting to see if this is literally true; that is, that Labs share these genetic traits with seals and whales.

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    1. Hi Jen – Very interesting point! It would be so neat to find out if this is a case of similar underlying genetic cause or one of convergent evolution. One does wonder though, why, if this is truly an adaptive trait as opposed to something that either “came along for the ride” as breeders selected for other traits, the gene mutation was not found in other breeds that also have a history of cold water work, such as Goldens and Newfoundlands. Regardless, it is an interesting theory and I hope someone examines it! Thanks for posting – Linda

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  3. I find myself wondering how much this might have to do with AKC judges promoting fat Labs in the show ring. It seems like judges ignore dogs unless they are at least 20 pounds overweight. This drives breeders to selectively breed for fat dogs. Such an unfortunate situation in a breed prone to hip dysplasia. I keep waiting for conformation showing to start rewarding healthy dogs of all breeds, but it seems that will not happen in my lifetime.

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    1. Hi Mary – It is a good question. Certainly, there may be selective pressure (even if unintentional) towards dogs who are more naturally stocky (fat?) if those are the dogs who are winning in the conformation ring. And I agree – putting up dogs who are overweight has been going on in many breeds for many years (Goldens are another unfortunate example). I think there has been a change in some breeds and some have happily never had this issue, but it certainly is a problem in some. Thanks for posting! Linda

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    2. There are two components to this.
      1. Yes, with Labs there’s a history of fat being rewarded in the show ring
      2. A sturdily built Lab with a good coat is likely to look fat, even when the touch test reveals that the ribcage is ‘well sprung’ but pretty bony.
      If you look at historical pictures, you’ll find that heavy build is not a new thing in Labs, and it has been argued (Mary Rosslyn Williams) that the leaner build found in some bloodlines has come in through interbreeding with hounds, in part because fence jumping has at times been important in field competition.

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  4. Hi Linda! I have a lab and really believed he had some genetic predisposition for food or mouth orientation, and now with your post here see he may also be one of these labs with the deletion. He is not overweight but has what could be called an obsession with food and we have limited him due to weight. I’m wondering if you have a dog who really always feels hungry and then is restricted if then they might develop some nervous type behaviors/habits? He didn’t start out being poop obsessed, but as we had to restrict him from being off leash due to immediate quest for finding carcasses and stuff that makes him sick, he has now taking up diving for poop he sees (well before I do) along the trails we walk on.

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    1. Hi Kathleen – So nice to hear from you! The first paper identified “excessive food motivation” as one of the defining characteristics associated with the gene deletion. We have definitely seen dogs like this in our classes (in fact, I often advise owners of these dogs to feed them prior to training, which is the opposite of our normal approach with using food treats as +R). I agree that limit feeding could lead to frustration and anxiety, especially if this tendency is highly influenced by heredity and has a smaller learned component. For dogs who are always incredibly hungry (and good for you to limit feed for your boy’s health, even in the face of his voracious appetite), we typically recommend selecting a food that is relatively low in energy density, which will allow you to feed a higher volume and hopefully will contribute to increased satiety. You may already do this, but if not, walking with very high value treats and being extremely generous with providing them to your boy can help with the “diving for poop” issue (along with teaching a solid “leave it”). Again, I realize you may already do all of these things. I know it is frustrating because when you limit feed him and these behaviors result, his quality of life is negatively affected in a myriad of ways (yours is, too!). Last, though we lean more towards harnesses, we still do use Gentle Leaders, especially for young dogs. If you need more control over your boy’s head (especially when +R him to “leave it”), that might be helpful to you, even if you do not use it all of the time. So sorry you are having these issues with your boy – I know how much you love your dogs and that, like us, you love to hike the trails with them. Hope this helps a bit – Linda

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