Diseases and Conditions Contributing to Obesity in the Dog.
Dogs may become overweight for many reasons. Whether the obesity is due to simple overfeeding or a result of a disease process, the bottom line is the same: the dog is taking in more calories than he is using. Regardless of the cause of obesity, the owner is ultimately responsible for regulating the dog's caloric intake and use, and in seeking veterinary assistance in maintaining the dog at the optimal weight. Humans are the main cause of obesity in dogs.
Some of the more common diseases and conditions which can contribute to obesity in the dog are discussed below.
Food type, availability and palatability. Some dogs will only eat what they need and do fine if their food is available free choice available al all times. Others will eat as much as is available and then look for more. Some dogs are finicky and others will eat just about anything. The amount and type of food that is fed and the eating tendencies of the dog can determine how likely it is a dog will become overweight.
The type of food fed has a direct bearing on the tendency of a dog to become overweight. Table scraps, treats, even premium high-energy dog foods can contribute to obesity. A 7 year old labrador whose main occupation is laying in front of the hearth does not need a high-energy dog food, whereas his brother who is a field dog and lives in an outside kennel has high energy needs and a premium high energy food is in order.
Activity level: Activity level plays a major role in determining the caloric needs of a dog and it's tendency to become overweight. An active dog will use more calories. In addition, an active dog's mental state may make it less likely to eat more because of boredom or stress.
Neutering and spaying: Neutering and spaying dogs lowers their metabolic rate such that they require fewer calories than intact dogs. In addition to changes in metabolism, androgens and estrogens (male and female sex hormones) stimulate roaming behavior and general physical activity. Estrogen, in addition, has the effect of decreasing appetite. Spayed animals never have the extra energy demands of pregnancy or raising a litter.
Since their energy needs are less, if we feed them what we would feed intact dogs, neutered and spayed dogs will, of course, gain weight. In truth, most neutered and spayed dogs are overfed and less exercised and are twice as likely to become obese as intact dogs. Neutering and spaying in themselves do not cause obesity, it's how we care for the dogs afterwards that predispose them to becoming overweight.
Genetics and breed predispositions: Are some breeds simply more prone to becoming overweight? The answer is yes. This doesn't mean all dogs of that breed may have the tendency, but it does mean owners of those breeds of dogs should be especially vigilant about monitoring their dog's weight. Those breeds which are more prone to becoming overweight include Labrador Retrievers, Dachshunds, Beagles, Cairn Terriers, Cocker Spaniels, Collies, Shetland Sheepdogs (Shelties) and Basset Hounds. Other breeds tend to have a lower incidence of obesity. I don't think I've ever seen an overweight greyhound, but I'm sure it does occur.
Genetic factors which influence the type and characteristics of fat produced by the body have been shown to contribute to obesity in rats and mice. Such factors may occur in dogs.
Age: Dogs tend to become overweight when they are between 2 and 12 years of age, especially around the 6 year mark. As dogs become "senior", the tendency to become overweight decreases. Young dogs, too, in general, are less likely to be overweight since their energy requirements are high since they are growing and are generally more active. A dog becoming overweight when under two years of age is a real warning sign. This dog will tend to be overweight it's entire life so weight reduction should occur as soon as possible and every effort should be made to maintain the optimum weight.
Social environment: Many people will acknowledge they eat more when they are stressed, and often eat less nutritious food. Animals have similar responses to stress. This stress could include new persons entering the household (e.g., a baby), changes in the household routine, etc.
Some nutritionists feel dogs may overeat simply because they are bored and there literally is not much else to do. Some dogs may not get into the garbage can because they are hungry but because they need something to do - the food they find is just a bonus.
Dogs who live in a multi-dog or even multi-pet households often tend to eat more and/or faster than those in one-dog households. The change in behavior when other animals are present is called "social facilitation". The competition for food, whether perceived or actual, makes some dogs much more focused on their food and can lead to obesity.
Physical Environment: Maintaining body temperature is an energy-consuming task. When a dog is in an environment with a temperature below freezing, it's calorie requirements may increase by as much as 30%. Conversely, an inside dog uses relatively few calories to maintain normal body temperature.
Medications: Various medications can influence metabolism and appetite. These include the glucocorticoids such as prednisone and dexamethasone, the barbiturates such as phenobarbital which is tised to control epilepsy, and a class of drugs called benzodiazepines which includes valium.
The following possible contributors to obesity account for less than 5% of the cases of obesity in humans, and a similar proportion is likely in dogs as well.
Hypothyroidism: ln the disease Hypothyroidism, the dog's body produces less thyroid hormone. Thyroid hormone influences metabolic rate. Less thyroid hormone means lower metabolic rate and lower energy needs. A normal dog will become overweight if it develops hypothyroidism and is fed the same amount it was fed when it was healthy.
Depending on the breed, many veterinarians will check an overweight dog for hypothyroidism before a weight reduction program is instituted. It is very difficult to get a hypothyroid dog to lose weight even when fed a weight reduction diet. By treating the hypothyroidism in conjunction with starting a weight control program, chances of success are much higher.
Cushings disease (hyperadrenocorticism): Cushings disease is a disease in which the adrenal gland produces too high a level glucocorticoids. Glucocorticoids can alter metabolism and canse an increase in appetite and an increased deposition of fat. Again, in addition to starting a weight control program, the Cushing's disease must be managed if the dog is to successfully lose weight.
Insulinoma: An insulinoma is a tumor that occurs in the pancreas. It is a tumor consisting of the cells that produce insulin. A dog with an insulinoma produces too much insulin. Insulin tends to increase food intake and promote the generation of tissue, including fat.
Adult onset diabetes: If an increase in insulin can contribute to obesity it seems contradictory that diabetes mellitus, in which there is decreased insulin production, could 'also contribute to weight gain. There is, however, in dogs a type of diabetes called non-insulin dependent diabetes mellitus (NIDDM) in which obesity can occur. It is one of those "which came first, the chicken or the egg" conditions. It occurs when an overweight dog must increase its insulin production which then causes an increase in appetite. Then as the disease progresses, the production of insulin can not keep up with the demand and increased blood glucose levels occur. The dog ultimately becomes diabetic and severely obese.
Pituitary gland and brain diseases: The pituitary gland is often called the "master gland" because it produces hormones itself and regulates the production of hormones from most oft he other glands, If the pituitary gland is functioning abnormally, changes in the levels of various hormones can change the dog's metabolism and appetite.
The hypothalamus in the brain regulates appetite. Hypothalamic abnormalities could account for rare instances of increased appetite resulting in obesity.
Health Risks in Overweight Dogs
As in people, dogs carrying extra pounds of weight place extra, demands on virtually all the organs of their bodies. When we overload these organs, disease and sometimes death are the consequences. The health risks to overweight dogs are serious and every dog owner should be aware of them. The more common consequences of obesity in dogs are discussed below. Diabetes mellitus (sugar diabetes)
One of the most common complications of obesity in dogs is the development of diabetes mellitus (sugar diabetes). Obesity causes all increase in the secretion of insulin in response to the increased blood glucose level in the overweight dog. Insulin is also more in demand simply because there is a greater amount of tissue in an overweight dog When requirements for insulin exceed the ability of the body to produce insulin, diabetes mellitus develops. If the need for insulin increases over a long period of time, the cells in the pancreas which produce insulin can actually "burn out", again resulting in diabetes. Damage to joints,, bones and ligaments
Studies have suggested that approximately one quarter of overweight dogs develop serious joint complications. The bones, joints, muscles and associated tendons and ligaments all work together to give the dog smooth and efficient movement. If they are required to carry excess weight, they can start to become damaged. Arthritis can develop and the pain and joint changes associated with hip dysplasia can become markedly more severe.
Extra tension on joints caused by an increased weight load can also lead to damage of certain ligaments. Ligaments are tough fibrous strands of' tissue that hold one bone in proximity to another bone in joints. One of the ligaments in the knee, the anterior anterior cruciate ligament is very prone to strains or tears. If this ligament is torn, the knee becomes very unstable and the dog is reluctant to use it. Surgery must be done to repair this torn ligament.
Certain breeds of dogs, such as dachshunds are prone to develop intervertebral disc disease ("slipped disc"). Carrying extra, weight increases the probability that they will develop this painful and sometimes debilitating condition.Heart disease and increased blood pressure
As in people, overweight dogs tend to have increased, blood pressure (hypertension). The heart has an increased work load since it must pump additional blood to excess tissues. This can lead to congestive heart failure. Difficulty breathing
In overweight animals the lungs can not function properly. The additional fat in the chest restricts the expansion of the lungs. The extra fat in the abdomen pushes against the diaphragm which separates the abdominal cavity from the chest. This also results in less space in the chest :for the lungs to expand on inspiration. To make matters worse, the increased quantity of tissue puts an increased demand on the lungs to supply oxygen. These changes are especially serious in dogs who may already have a respiratory disease. Decreased stamina
Dogs who are overweight have less endurance and stamina. Carrying all that extra weight around takes a lot more work. The heart, muscles and respiratory system are all asked to do more than they were designed for. Heat intolerance
Fat is an excellent insulator which is fine if you are a polar bear. But if you are an overweight dog in the heat of summer, the excess fat can make you miserable, and much less capable of regulating your body temperature. Decreased liver function
The liver stores fat so when a dog is overweight, an increased amount of fat builds up in the liver. This is called hepatic lipidosis. This condition can result in decreased liver function. Increased surgical and anesthetic risk
The effects of obesity on the heart and lungs have serious ramifications during anesthesia. Cardiac arrest (heart stops) and poor circulation of oxygenated blood to the tissues can occur.
Many of the anesthetics are taken up by fat, so an overweight animal will take longer to come out of anesthesia because the anesthetic must be removed from the fat by the body. In addition, many anesthetics are broken down by the liver. A fatty liver may not be as efficient at breaking down anesthetics and other drugs, so again, recovery may be delayed.
The increased fat in the tissues makes surgery more difficult. Basically it's harder to find or get at what you are looking for. The fat obscures the surgical area. For example, in abdominal surgery in an obese dogs there may be literally inches of fat between where the skin incision is made and the organ you need to work on, such as the urinary bladder. This makes the surgery technically more difficult and the procedure will also take longer, which again increases the anesthetic risk.Reproductive problems
Overweight clogs tend to have more problems giving birth than dogs at their optimum weight. This difficult: birthing is called dystocia. Dogs experiencing dystocia often need veterinary assistance to deliver their pups, and may require a caesarean section (C-section). Digestive disorders
An overweight dog has an increased risk of developing constipation and may also have more problems with intestinal gas and flatulence, which is not pleasant for the dog or the owner! Decreased immune function
Obesity in the dog is associated with decreased resistance to viral and bacterial infections. Canine distemper- and Salmonella infections, especially, seem to be more severe in dogs who are overweight. The exact cause(s) of this lowered resistance to disease in obese dogs is unknown. Skin and hair coat problems
The risk of skin and hair coat diseases are increased in dogs who are overweight. The skin forms more and different types of oils, the skin may fold in on itself creating pockets which are ideal for the accumulation of oils and the development of infections. Increased risk of cancer
The exact link between obesity and developing certain cancers is unknown. However there have been studies which suggest that obese clogs tend to have an increased risk of developing certain types of cancers, including a particular type of cancer of the urinary bladder. A recent study also found that dogs who were obese at one year of age were at greater risk of developing mammary- tumors. Decreased quality and length of life
lit is evident from the above discussion that the health, ability to play, even to breathe, are diminished in overweight dogs. Overweight dogs may become more irritable due to being hot, in pain, or simply uncomfortable. Overweight dogs die at a younger age than those maintained at an optimum weight.. It is clear that we are not contributing positively to our dog's health when we allow them to become overweight. The next time those big brown eyes say, "Can I please have a treat," think very carefully first. In most cases your answer should be "No, and I'm doing this for your own good," and it will be absolutely true.
© 2000 Drs. Foster & Smith, Inc.