Obesity, Appetite, and a Gene Mutation in Labrador Retrievers
Weight Gain in Labrador Retrievers
Labrador Retrievers are usually affectionate dogs that make wonderful pets. Unfortunately, some have a tendency to gain weight. In fact, pet experts often mention the breed as the one that is most likely to become obese. In some dogs the weight gain is probably caused by a high calorie intake and insufficient exercise. There may be another factor at work, however. Researchers have discovered that a significant percentage of Labs have a gene mutation linked to increased weight. The mutation may prevent their hunger from being satisfied and increase their obsession with food.
Misha is my Labrador Retriever. Like most Labs, he loves to eat. We mustn't assume that a dog who eats a lot has a genetic problem that increases their hunger. Even if a dog has the mutation, the steps for keeping him or her at a healthy weight are the same. The task may be harder in an animal with the mutated gene, though.
Dog Obesity Statistics
The research into the gene mutation in Labrador Retrievers was carried out by a group of twenty-two scientists. Most of them are associated with the University of Cambridge Metabolic Research Laboratories. Based on a survey of the scientific literature, the researchers have discovered the following facts.
- In developed countries, between 34% and 59% of dogs are obese.
- Recent increases in canine obesity and in diseases linked to the obesity mirror changes seem in humans.
- Despite the above facts, obesity is more common in some dog breeds than others, suggesting that genetics plays a role in the disorder.
Of all dog breeds for which data have been reported, Labrador retrievers have the greatest documented obesity prevalence .... and have been shown to be more food motivated than other breeds.— Cell Metabolism Journal Article
A Gene Mutation That May Affect Hunger and Appetite
The gene that is linked to a Labrador Retriever's weight gain and obesity is known as the POMC or pro-opiomelanocortin gene. (There may be other genes that can also cause Lab obesity.) The mutation consists of the deletion of a section of DNA from the gene. DNA, or deoxyribonucleic acid, is the chemical that makes up genes. Genes contain coded instructions for making proteins. If a section of DNA is missing, so is part of the instructions.
The POMC gene codes for a protein that splits up to form two neuropeptides: beta-MSH (melanocyte-stimulating hormone) and beta-endorphin. As a result of the mutation, the production of the neuropeptides is assumed to be disrupted. This assumption wasn't tested in the research, however. The chemicals are thought to play an important role in ending the sensation of hunger once a dog eats, although there are other chemicals and brain pathways involved in ending hunger.
When the dog experiences a weaker signal "telling" it that it's no longer hungry, its appetite may not be completely satisfied even after it has eaten what should be a sufficient amount of food. This may be the reason for the increased food searching behaviours and weight observed in many dogs with the mutation.
Prevalence of the Mutated Gene
The mutated gene was found in about a quarter of the 310 Labrador Retrievers involved in one trial carried out by the researchers. In another trial involving a total of 411 dogs from the United States and the UK, researchers found that 23% of the Labrador Retrievers had the mutated gene. The dogs included both companion and assistance animals. Interestingly, the gene was discovered in 76% of the 81 assistance dogs that were checked. The greatly increased percentage in assistance dogs was surprising to the researchers.
Genes give dogs and humans many of their characteristics. A gene exists in slightly different variations called alleles. The combination of alleles that an animal possesses for a certain characteristic is known as a genotype. The mutated POMC allele in dogs was apparently able to exert its effect whether it was present in a heterozygous genotype (one normal version of the gene and one mutated form) or in a homozygous genotype (two mutated forms of the gene). Dogs with both of these genotypes were often overweight or obese.
Effects of the Mutation
According to owner reports, dogs with the mutation are more motivated to find food than dogs without the mutated gene and perform behaviour such as food scavenging and begging more often. In addition, most of the dogs in the experiment who had the mutation were significantly heavier than their counterparts without the mutation. Many were overweight or obese. This wasn't true for all of the dogs with the mutation, however. This may have been due to diligent food and portion control by the owners.
The researchers discovered that some dogs without the mutation were obese, which shows that there are additional factors—genetic or otherwise—that control body weight in Labs.
The mutated gene has been found in flat-coat retrievers and has been linked to obesity in that breed. Flat-coated retrievers are close relatives of Labs. Some mice, rats, and humans also have POMC genes associated with obesity. The mutated dog gene is most similar to the one in humans, which means that research in dogs may be helpful for us as well as our canine companions.
Assistance dogs are trained to help people with a disability. Some examples of disabilities that can be helped by a well-trained assistance dog are blindness, hearing loss, and paralysis.
Assistance Dogs and a POMC Gene Mutation
The researchers have an interesting hypothesis for the greatly increased prevalence of the mutation in assistance dogs. They emphasize that their hypothesis is only a possibility and needs to be tested. Assistance dogs are generally given food rewards when they perform a desired behaviour, at least in the first stage of their training. Therefore all other things being equal, a dog that is more strongly motivated by food could be easier to train and make a better assistance dog. Adult dogs who possess the POMC mutation and pass it to their offspring might be seen as producers of the best puppies and favoured as parents. The mutation would therefore become more common in the assistance dog population.
The hypothesis sounds quite plausible, although I do wonder whether an assistance dog with the POMC mutation could become so distracted by the presence of nearby food that they no longer do their job properly. Ignoring temptation would have to be a major part of their training.
I got Misha from a lady who breeds her dogs to produce puppies for the Pacific Assistance Dogs Society (PADS). The plan was to train some of Misha's litter for PADS. Misha has an unusually strong interest in finding food compared to my other Labs. The combination of these factors makes me wonder if Misha has the POMC mutation. Identifying the presence of the gene would certainly make me feel sorry for him but wouldn't change the steps that I need to follow in order to keep him at a healthy weight.
If your dog needs to lose a significant amount of weight, it's important to consult a vet. Intensity and frequency of exercise and the introduction of an effective but safe diet are important considerations.
How to Keep a Dog at a Healthy Weight
The following steps should enable a dog to maintain a healthy weight. They are especially important for a Labrador Retriever that may have a gene that contributes to weight gain and obesity. If your dog gains weight even after the steps are being followed, it's a good idea to see a vet. The dog may have a medical problem that causes weight gain, such as hypothyroidism.
- Feed your dog an adequate amount of food at meal times and make sure that the food is healthy and nutritious.
- Check with a vet or your breeder if you have any doubts that your dog is being given enough (or too much) food. Labels on dog food packages may be a useful guide but may not be completely reliable.
- Check your dog's weight frequently. Ask your vet whether the dog is at a suitable weight and check whether any adjustments to diet or exercise are needed.
- Consider the use of treats very carefully. Multiple people in a family giving high calories treats to a pet at different times of the day can cause weight gain. If you want to give treats, examine their nutrition and calorie content and decide when and how often the dog will be given the treat.
- Don't give your dog food from your meal while you're eating. Even as a puppy, a dog should be trained not to beg at the table. If human food is given to a dog, it should be part of their regular meal. (Be very careful if you do this. Some human foods are dangerous for dogs.)
- Some dogs can be very cute and persuasive when they beg for food. They quickly discover behaviour that their owner finds hard to resist. Harden your heart and don't succumb if your dog begs. That being said, if a dog repeatedly asks for food even when you don't capitulate, you should consider why they are behaving in this way.
- Give your dog regular and sufficient exercise. The type of exercise is also important to consider. Some dogs require a more vigorous workout than others.
Any dog with a problem involving food intake should be checked by a vet. It shouldn't be assumed that the condition must be a behavioural or genetic problem. There may be a medical reason for the situation.
Food Stealing and Scavenging in Dogs
Food stealing and scavenging can not only cause a dog to gain weight but can also be dangerous if the dog eats certain foods. It can also be bad for oral health. Misha is a lovely dog and is generally well behaved, but he has stolen food in the past. I make sure that I keep most food out of his reach now. Training and discipline have definitely improved his behaviour and he does leave food alone when I tell him to. Food is still a big temptation for him, though. It's not his only interest in life, but it's a major one.
Of course, training and discipline mustn't hurt a dog either physically or psychologically. Every prospective dog owner should do some research to discover safe and effective ways to train and discipline a puppy or a dog before they bring it into their home.
There are at least two important reasons for hiding certain foods from all dogs. One is that some foods commonly eaten by humans are unsafe for dogs and should never be eaten by them. Another is that eating a large amount of food very quickly has been associated with bloat, a potential deadly condition in dogs. Raiding a large bag of dry dog food is especially dangerous in this regard.
Like humans, an overweight or obese dog has an increased risk of developing a variety of diseases, including cardiovascular problems, breathing difficulty, diabetes, joint disorders, and cancer. The dog is also at risk for a reduced lifespan.
Tips for Preventing a Dog From Stealing Food
There are two ways to prevent a dog from stealing food: train them to leave food alone or hide it from them. I use a combination of both methods. Training is especially important when a dog scavenges outside the home where food can't be hidden.
Here are some tips for hiding or removing food so that a dog can't get to it. I follow many of them myself.
- Make sure that all food is put out of a dog's reach as soon as it's brought into the home. An enclosed area such as a high cupboard or a refrigerator is best.
- Don't leave food on a table, counter, or other exposed surface in your home.
- If you're in the middle of making a meal in the kitchen and need to leave the room with food exposed, the kitchen door should be closed. If this isn't possible and your dog likes to counter-surf, the dog should be supervised by someone else or placed in a secure and comfortable area such as their crate.
- If you have to leave a meal before finishing it and your dog isn't trustworthy when food is temporarily unattended, ask someone else to watch the meal, take the meal with you, or place it in an inaccessible place.
- Store unused pet food in a secure area.
- If your dog steals another pet's food as soon as your back is turned, supervise the other pet as it's eating or feed it in an area that is inaccessible to your dog.
- Remove food left or dropped by other pets to prevent your dog from scavenging.
- Place food scraps, empty food containers, and garbage in a secure container or a place that your dog can't reach.
- Don't leave your dog alone in a car with either human or pet food.
Learning More About the POMC gene
Hopefully researchers will soon learn more about the mutated POMC gene and the way in which it affects both dogs and humans. I would also be interested in research that compares the frequency of the mutation in show line and field line Labrador Retrievers. Show line dogs are generally stockier animals than field line ones.
It would be wonderful if researchers found a way to safely compensate for the effect of the mutated gene by biological or chemical means. Until then, dog lovers should try to keep their Labrador Retrievers at a healthy weight to reduce the chance of disease and to help them enjoy life more.
Why Labrador Retrievers are more interested in food than other breeds: a news release for the general public from the Cell Metabolism Journal
A Deletion in the Canine POMC Gene: the research report from the Cell Metabolism Journal
Weight problem in Labradors from New Scientist
Obesity in dogs from PetMD
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
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© 2016 Linda Crampton