TOPICS OF INTEREST :: CANINE OBESITY

Canine Obesity: The Health Risks You Don't See

Obesity is a disease that needs to be treated

Obesity in dogs is a serious medical problem. Fat dogs are more at risk in surgery, more prone to injury, and have more stress on heart, lungs, liver, kidneys, and joints. Excess weight can worsen osteoarthritis, cause respiratory problems in hot weather and during exercise, lead to diabetes mellitis, and generally lessen the quality of life for a family pet.

An owner can control his pet's weight by realizing that food is not a substitute for attention or a cure for guilt and that firmness can and should be applied to the relationship. An owner who cannot resist Fluffy's soft, pleading eyes whenever food enters the vicinity is an owner contributing to Fluffy's obesity and may even be shortening her life. An owner who cannot rouse himself for a few hours each week to make sure that Singer gets enough exercise is an owner contributing to Singer's obesity and may even be shortening his life. Obesity affects a dog's energy balance and other physiologic functions. Preventing obesity through a healthy lifestyle is ideal, but once a dog is obese, weight loss is critical to improve the pet's overall health.

Diet and exercise are often not enough

Obesity sometimes cannot be treated by diet and exercise alone. There are other pathophysiologic factors that affect a dog's ability to lose weight and can be the reason previous weight loss attempts have failed.

When dogs become obese, their bodies begin to work against them. Changes in their bodies can lower their metabolism, increase their appetite, and even other serious medical conditions.

Associated conditions, such as arthritis, can be a possible common factor

Obesity is just as important as and urgent as any other medical condition. Relate canine obesity to human health issues. Most people understand that obesity is dangerous to human health, but may not know that dogs are also prone to many of the same risks.

Just like humans, that extra weight on your dog is associated with some serious conditions like arthritis, respiratory disorders, and more. If your pet already has a condition because of his/her obesity, it is important to know how obesity may have caused it or is making it worse.

Excess weight can affect your dog's health and put a strain on his or her lungs and joints. In fact, that weight may be making your dog's arthritis even worse. Losing weight can help take some of the burden off his or her joints.

A Risk Factor for Osteoarthritis

Canine obesity is on the rise. Current estimates indicate that, on average, 25% to 40% of pets in the United States are either overweight or obese. In fact, researchers found that more than 40% of all dogs 6 to 10 years of age are overweight or obese. A dog is generally considered to be overweight if it is 5% to 19% above its ideal body weight.

Obesity is a serious medical problem

The cause of obesity in dogs is multi factorial. Certain medical conditions make it difficult for dogs to maintain a healthy weight, and certain dog breeds may be predisposed to becoming obese. However, in most dogs, obesity is an insidious condition that develops over time as a dog consistently consumes more energy than it is expending. This can result from increased caloric intake (eating too much food), not getting enough exercise, or a combination of these two factors.

Obesity is not just a nuisance or an inconsequential medical finding. There is growing evidence connecting obesity in dogs to the development of osteoarthritis (OA), a common and significant orthopedic problem. Several studies have examined this association, and investigators are looking for ways to successfully manage both of these potentially devastating chronic conditions.

Obesity Damages Joints

OA develops when the normal balance between synthesis and degradation of joint structures is disrupted. It has been theorized that increased mechanical stress on joints (caused by body weight) contributes to the degradation of articular cartilage and subchondral bone over time, leading to the development of OA; however, the full extent of the connection between obesity and OA is likely deeper and is not yet fully understood.

Several studies in dogs have shown a significant increase in the risk of OA associated with obesity. In one group of studies, Labrador retriever litter mates were paired at 8 weeks of age according to sex and body weight and followed for several years to investigate the occurrence of OA as the dogs aged. Each day of study, one dog from each pair was fed ad libitum and the paired mate was fed 25% less food than the other dog. All dogs in the study received the same diet, were weighed regularly, and were monitored periodically for evidence of degenerative joint disease (DJD). In the first of these published studies, the dogs had been followed for 5 years and monitored for the development of DJD involving the hips. Investigators reported that dogs fed ad libitum weighed more, had four times the incidence of hip DJD, and developed OA earlier and in more severe form than did their restricted-diet litter mates.

In the follow-up study involving the same group of dogs, DJD affecting the elbow, shoulder, and stifle joints were evaluated until the dogs were 8 years old. Investigators reported that prevalence of OA involving multiple joints were increased for dogs that were fed ad libitum. Because the dogs in the study were age- and sex-matched with litter mates, maintained under identical husbandry and living conditions, and fed the same diet with the exception of quantity, it is unlikely that significant differences in OA progression were related to anything besides quantity of food intake.

Although any breed can develop OA, certain breeds are overrepresented. For example, among golden retrievers, hip dysplasia (an inherited disease that leads to the development of OA) has been reported to be as high as 73%. One might expect that if a dog has a breed disposition for OA, food intake and subsequent weight gain would not have as much influence on eventual development of OA. However, in the study comparing the incidence of DJD among golden retrievers, Rottweilers, German shepherds, and Labrador retrievers, weight was a significant risk factor for the development of DJD in all of these breeds for dogs older than 2 years of age. These studies further illustrate how excess weight can increase the risk of OA and alter the severity of the disease once it begins to develop.

Weight Reduction Can Improve Clinical Signs of OA

Overweight dogs had a higher incidence of medical conditions associated with obesity compared to their leaner counterparts. Unfortunately, once a dog develops OA, the condition is not curable; the veterinarian and pet owner need to work together to slow the progression of the disease as much as possible and improve the overall quality of life for the patient.

NSAIDS have long been the cornerstone of OA management, and these drugs are still important for their ability to relieve pain and decrease inflammation. However, a multi modal approach including NSAIDs, weight control, environmental modifications, and controlled exercise is the preferred approach for long-term OA management. Excess weight is an important risk factor for OA in dogs, and weight loss in a dog that already has OA should be a critical element of an overall management plan aimed at improving mobility, comfort, and joint function for the pet. For some dogs, this is very difficult goal to accomplish. A dog that experiences too much pain during exercise will refuse to exercise. Therefore, a dog with OA that is also obese will have a limited ability to exercise and a hard time losing weight because calorie burning through exercise will be limited. Similarly, if a dog experiences pain and alters its gait and movement to compensate, that adjustment can increase the weight load on previously "normal" joints and contribute to the development of DJD in those joints down the road. This occurs in dogs of normal weight but is exacerbated in dogs that are overweight.

Fortunately, studies have shown that weight loss has a very positive effect on the clinical signs in dogs with OA. In one study by Mlacnik and colleagues, 29 arthritic, overweight dogs received identical caloric restriction and either home-based physical therapy or more intensive physical therapy. At the end of the study, dogs in both groups had lost significant weight, although weight loss in the intensive physical therapy group was more pronounced. Combining weight loss with physical therapy improved clinical signs associated with OA, increased comfort and mobility, and facilitated further weight loss.

Another report from Impellizeri and colleagues demonstrated that weight loss alone improved clinical signs of arthritis. This study involved nine client-owned dogs with OA involving the hips. All the dogs were at least 11% above their ideal body weight at the beginning of the study, and owners were instructed to begin feeding their pets 60% of the calories that would be needed to maintain the current body weight. During the course of the 19-week study, calorie restriction resulted in weight loss ranging from 11% to 18% of initial body weight. No OA medications or supplements were administered during the study, and the owners were instructed not to change their dog's exercise regimen; all of the dogs in the study were relatively sedentary. By the end of the study, all the dogs had improved clinically, as evidenced by reduced lameness while walking or trotting. These findings reinforced the importance of weight loss as a critical component for long-term success.

Make the Connection Between Obesity and Osteoarthritis

Veterinarians can become part of the solution to the rising canine obesity rates by discussing obesity with pet owners more often and with conviction. Ideally, veterinarians should begin a dialogue about nutrition during the pet's first office visit.

Pet owners should understand the risks of pet obesity before they take action to improve the health of their pet. Some facts to consider include:

• Arthritis is a chronic, progressive, incurable disease. It can affect all dogs, regardless of size or breed, and it can affect any joints in a dog's body, including those in the neck, back, hips, and legs.
• Signs of arthritis can be subtle. Some dogs with arthritis are obviously lame when they walk or run, but other dogs with the disease may walk fairly normally. Instead, they may stand or sit different or have trouble jumping into the car or using the stairs. In some cases, there aren't any obvious signs. I can examine your dog to determine whether he or she has arthritis or is at increased risk developing the disease.
• Additional weight can increase your dog's chances of developing arthritis. This can also make arthritis more severe when it does occur. Keeping your dog at an ideal weight can lessen these chances.
• Weight loss can improve lameness associated with arthritis. Weight loss can't cure this chronic disease, but it can help your dog move better and experience less pain.

Ideally, weight loss should be achieved as part of a treatment plan that may include pain medication, physical therapy, and other therapies aimed at improving comfort, decreasing inflammation, and Improving mobility. Weight loss can sometimes be accomplished through diet and controlled exercise alone, but some dogs need more help. Joint with osteoarthritis

Making the Connection to Respiratory Conditions

When a dog presents with respiratory difficulty, most veterinarians auscult the thorax for evidence of cardiac abnormalities or unusual lung sounds, but how many assess the dog's body condition score (BCS) to determine if obesity might be part of the problem? Research has identified obesity as an important risk factor for several respiratory conditions in dogs. With obesity now increasingly being thought of as a disease, veterinarians should recognize its health implications and be aware that many serious medical conditions, including respiratory illness, can be exacerbated by obesity. Some respiratory conditions, such as exercise intolerance, generally have a slow, insidious progression and are not considered acutely life-threatening. In contrast, problems such as collapsing trachea and heat intolerance can quickly become medical emergencies. In order to provide quality medical care to our patients and relevant education to pet owners, veterinarians need to understand the connection between obesity and respiratory disease in dogs and incorporate this understanding into our diagnostic assessment and management of respiratory disease.

Obesity Alters Respiratory Function and Contributes to Exercise Intolerance

Studies have shown that obesity can have a direct effect on a dog's breathing and respiratory function. Obesity leads to decreased lung expansion and increased work during breathing, both factors that contribute to increased exercise intolerance.

In a study of 36 client-owned retrievers. Researchers reported a two-fold increase in airway resistance for markedly obese dogs during periods of hyperapnea compared with the same dogs during normal breathing at rest, indicating respiratory dysfunction associated with obesity in these dogs. Retriever breeds were selected in part because of their similarities in size, body conformation, and popularity as pets. Chesapeake Bay, golden, and Labrador retrievers were represented in the study. Dogs ranged in age from 1 to 10 years, and none of the dogs in the study had preexisting cardiopulmonary disease. The researchers divided dogs into groups based on BCS using a 9-point scale:

• Not obese (BCS of 4.5 to 5.5; n = 11)
• Moderately obese (BCS of 6.0 to 6.5; n = 14)
• Markedly obese (BCS of 7.0 to 9.0; n = 11)

During normal breathing at rest, there was no difference in airway resistance among groups. But during hyperapnea, markedly obese dogs had significantly higher airway resistance compared with dogs that were not obese. The markedly obese dogs also had significantly higher airway resistance during hyperapnea than they did at rest.? In other work by researchers, overweight dogs with a BCS ranging from 5 to 9 (also using a 9-point scale) were studied. The dogs in this study were sedated, and fluoroscopy was used to measure the dimensions of the thoracic cavity throughout the phases of respiration. These authors reported that the diaphragm shifted cranially with increasing obesity, likely due to intra-abdominal fat. This led to oppression of the thorax, which also worsened as obesity increased. These findings highlight the significance of obesity as a condition that impedes normal respiratory functioning in an otherwise healthy dog. In a clinical setting, this information can help veterinarians identify potentially at-risk patients and help clients address weight management before the problem progresses to a point where consequences are observed. Weight reduction has been associated with improved clinical signs in dogs with chronic respiratory diseases. For overweight dogs, veterinarians should recommend weight loss as an important part of any treatment plan.

Obesity Exacerbates Collapsing Trachea

For patients with some preexisting respiratory problems, obesity can also play a role in how the illness progresses and how veterinarians manage the patient over the long term. For example, obesity has been implicated as a trigger of clinical signs for dogs with sub clinical collapsing trachea.

Collapsing trachea occurs when tracheal cartilage loses some of its rigidity, causing the tracheal rings to become flattened doro ventrally and the dorsal tracheal membrane to develop laxity. The net result is a dynamic narrowing of the trachea, frequently associated with exertion and often accompanied by a cough.

Certain breeds such as Yorkshire terriers are predisposed, but the risk factors of the syndrome are multi factorial. In fact, some dogs that have an anatomic tendency to develop tracheal collapse may remain asymptomatic until a secondary factor initiates the development of clinical signs." Risk factors for the development of clinical signs include cardiac disease, pneumonia or bronchitis, and laryngeal disease, but obesity has also been identified as an important systemic contributing factor. In one study of 62 dogs diagnosed with collapsing trachea, only one dog (1.6%) was underweight, and 15 (24.2%) had normal BCS scores; however, 46 of the dogs (74.2%) were overweight, with a BCS ranging from 6 to 9 on a 9-point scale.

Obesity can worsen the severity of respiratory problems such as collapsing trachea by causing dynamic changes in airway diameter or compliance, which promotes turbulence at high flow rates.' Also, fat deposits within the thorax can interfere with respiration by causing a reduction in thoracic wall compliance." These changes can become problematic during exertion or exercise, contributing to the severity of clinical signs observed with collapsing trachea and other airway diseases.

Managing collapsing trachea can be challenging, especially when clinical signs are severe or persistent. Medical and surgical options are available but typically only offer limited improvement. Obesity exacerbates clinical signs and must also be addressed. Because certain types of exercise can trigger episodes of coughing and respiratory distress in dogs with collapsing trachea, other weight-loss measures are generally necessary to achieve significant weight reduction. Nevertheless, weight reduction should be pursued aggressively as part of the overall treatment plan because weight loss has been shown to improve respiratory function in dogs with collapsing trachea and other respiratory conditions.

Obesity Exacerbates Heat Intolerance and Adversely Affects Patient Prognosis

Thermo regulation requires a steady balance between heat production and dissipation. Body heat is produced continually through mechanisms such as metabolism and muscle activity. In dogs, the most important mechanisms of heat dissipation are convection (cool air moving across the skin, allowing heat from the dog to transfer to the air), radiation (release of heat into the environment), and evaporation through panting. Under normal conditions, convection is a reliable method of heat dissipation in dogs. But as the ambient temperature approaches the dog's body temperature, convection becomes less important and dogs rely more heavily on evaporation (panting) for Thermo regulation. As a result, decreased ability to dissipate heat through panting is an important risk factor for heatstroke. Dogs with airway abnormalities have inefficient ventilation and are therefore unable to effectively dissipate heat through panting. These at-risk dogs include brachycephalic dogs and dogs with laryngeal paralysis or collapsing trachea. Dogs that are obese also have decreased ventilation and an impaired ability to dissipate heat due to increased insulation provided by excess body fat, raising their risk of developing heatstroke. When heatstroke occurs, the balance between heat production and dissipation is disrupted and body temperature can increase to life-threatening levels. Research has shown that obesity increases the risk of heatstroke in dogs and complicates the condition when it occurs.

In dogs, heatstroke can be nonexertional or exertional. Nonexertional heatstroke is a danger for dogs confined in an overheated area, particularly when humidity is high. This includes dogs that are chained outside without adequate water or shade and dogs that are locked in a car during warm weather. Exertional heatstroke tends to occur in conjunction with increased muscle activity. Interestingly, athletic dogs, such as working dogs and racing greyhounds, tend not to develop heatstroke even when they exercise in hot weather. One possible explanation for this might be increased vigilance by handlers, but being well hydrated and well acclimated are also factors. Being physically fit may also be a factor, because obese dogs are at increased risk for exertional heatstroke, as are dogs with airway abnormalities such as laryngeal paralysis.

Not only does obesity predispose a dog to heatstroke, but it increases the likelihood of death when heatstroke occurs. A 2006 retrospective study evaluated mortality among a group of 54 dogs diagnosed with heatstroke.t? Although only 20% of the dogs in the study were obese, they were almost twice as likely to die as dogs that were not obese. Investigators reported that 82% of obese dogs died, compared with 42% of dogs that were not obese (p= .040), and identified obesity as an independent risk factor for heatstroke-related death.

These findings highlight the effect of obesity on heat intolerance. Not only is decreased heat dissipation (secondary to body fat) a risk factor, but compromised airway functioning further contributes by limiting heat dissipation through panting. Veterinarians can use this information to identify at-risk patients, communicate these risk factors to owners, and help owners initiate successful weight reduction measures for overweight dogs.

Make the Connection between Obesity and Respiratory Conditions

Obesity has a direct connection to several important respiratory conditions in dogs. Some of these issues, such as heat intolerance, can be immediately life-threatening, whereas others, such as exercise intolerance, can have a profound but long-term effect on quality of life. Some things to bear in mind:

• "Obesity can cause respiratory changes. Overweight dogs are more prone to certain breathing problems so maintaining a healthy weight is very important."
• "Weight loss can improve some breathing problems. Conditions such as collapsing trachea and exercise intolerance can be improved when a dog loses weight. Weight loss is a crucial element in your dog's management and treatment plan.
• "Dogs with respiratory conditions, particularly exercise intolerance and airway disease, may have problems losing weight because of their inability to exercise or otherwise increase their activity level. Some of these dogs may experience weight reduction through diet alone, but many of them may need more help. If you have not been able to reduce our dog's weight through diet.