Showing love to our canine companions often includes giving treats, but this can inadvertently lead to weight gain that threatens their heart health. The extra pounds that make your dog seem cuddlier actually place serious strain on their cardiovascular system , potentially causing long-term damage.
Studies indicate that a large percentage of dogs in developed countries struggle with being overweight or obese. Beyond the more commonly known issues like joint problems and reduced energy, obesity places tremendous strain on your dog's cardiovascular system, potentially leading to long-term damage. This article aims to help you understand how those extra pounds affect your dog's heart and what you can do to ensure your beloved friend lives a long, healthy life.
Summary
The connection between excess weight and heart function
Veterinarians often use the Body Condition Score (BCS) to assess whether your dog is at a healthy weight. This practical tool typically uses a 9-point scale, where 4-5 indicates a normal, healthy weight, while 7-9 signifies that a dog is overweight or obese. This assessment involves both visually looking at your dog's body shape and feeling for their ribs.
If you can easily feel the ribs with a thin layer of fat, your dog is likely at a healthy weight. However, if the ribs are difficult to feel under a moderate to thick layer of fat, your dog may be overweight or obese. When a dog's observed body weight is more than 15% greater than their ideal weight , they are considered obese.
Your dog's cardiovascular system includes the heart and blood vessels. Like in humans, the heart's job is to pump blood throughout the body, delivering oxygen and nutrients. When your dog carries extra weight, their heart must work much harder because there's more body mass that needs blood supply.
This increased workload can lead to cardiac remodeling , where the heart's structure and function change over time in response to the added stress. These changes, while initially a way for the heart to cope, can eventually become detrimental to its long-term health.
How obesity directly affects your dog's cardiac health
Structural changes in the heart
One significant way obesity affects the heart is by causing Left Ventricular Hypertrophy (LVH). This means the muscle of the left ventricle, the heart's main pumping chamber, becomes thicker. Studies using echocardiography have shown that obese dogs often have increased thickness in the left ventricular free wall and the interventricular septum. The good news is that significant weight loss can lead to a reduction in these systolic wall dimensions , suggesting that some remodeling might be reversible.
Obesity can also lead to changes in the size of the heart chambers. Some studies have observed an increase in the left ventricular internal diameter during both systole (when the heart contracts) and diastole (when the heart relaxes and fills with blood) in obese dogs. Other research has noted a decrease in the actual thickness of the heart walls in obese dogs, reflecting the complex ways the heart adapts under stress.
Functional impairments of the heart
Beyond structural changes, obesity can significantly impair how well your dog's heart functions. Systolic function, the heart's ability to forcefully contract and pump blood, can be reduced in obese dogs. This is often reflected in lower measurements of ejection fraction (%EF) and fractional shortening (%FS).
Diastolic dysfunction is another common issue. This refers to the heart's difficulty in relaxing properly between beats, which impairs its ability to fill with blood. Studies using Tissue Doppler imaging have found evidence of impaired relaxation in obese dogs. While weight loss can improve some structural changes, improvements in diastolic function may take longer or may not be as readily apparent.
The role of oxidative stress
Obesity isn't just about excess fat; it also creates an imbalance called oxidative stress . This occurs when there's an overproduction of harmful free radicals and not enough antioxidants to neutralize them. In obese dogs, this oxidative stress is often measured by an increase in malondialdehyde (MDA) in the blood.
This increased oxidative stress is thought to negatively impact heart muscle cells and contribute to cardiac dysfunction.
Impact on heart rate variability
Heart Rate Variability reflects the subtle variations in time intervals between heartbeats. It indicates the balance between the sympathetic and parasympathetic nervous systems, and a healthy heart shows good variability.
Research suggests that obese dogs may have impaired HRV, indicated by lower values in time-domain parameters like mean NN, SDNN, and RMSSD. They may also have an increased LF/HF ratio, suggesting increased sympathetic activity. However, some studies have not found evidence of decreased HRV in obese dogs, highlighting that this area is complex and may vary between individual dogs and breeds.
Protecting your dog's heart health
Understanding how obesity impacts your dog's heart is the first step towards protecting their well-being. The structural and functional changes we've discussed can significantly affect your dog's overall health. You might notice they have less energy, tire more easily during walks, or even develop signs of heart disease or heart failure.
Regular veterinary check-ups are essential . Your veterinarian will assess your dog's weight and BCS and perform a thorough physical examination. If concerned, they might recommend further cardiac evaluations, such as an echocardiogram or electrocardiogram (ECG).
The most crucial step for protecting your dog's heart is managing their weight effectively . Weight loss is key to mitigating the negative effects of obesity on the heart and can even reverse some structural changes. Here are practical tips for helping your dog achieve and maintain a healthy weight:
Consult your veterinarian about diet: don't try to put your dog on a diet without professional guidance. Your vet can recommend an appropriate weight-loss diet that is nutritionally balanced and helps your dog lose fat while preserving lean muscle mass. They will also help calculate correct portion sizes based on your dog's ideal weight and metabolic needs.
Implement controlled exercise: gradually increase your dog's physical activity, considering their current fitness level and any existing health conditions. Start with shorter, more frequent walks and gradually increase duration and intensity. Swimming can be an excellent, low-impact option.
Monitor progress regularly: track your dog's weight and BCS consistently. Your veterinarian will likely want follow-up appointments to monitor progress and adjust the weight management plan as needed.
Be patient and persistent: weight loss takes time and commitment. Work closely with your veterinarian and ensure everyone in the household follows the plan. Avoid giving extra treats or table scraps that can sabotage your efforts.
Early intervention is always better . Addressing weight issues before significant cardiac damage occurs can make a huge difference in your dog's long-term health and quality of life. Studies show that significant weight and fat mass reduction can improve some cardiac structural changes.
Partnering for your pet's cardiac well-being
Obesity has a profound impact on your dog's heart health. It can change the heart's structure, impair its ability to pump and fill with blood efficiently, increase harmful oxidative stress, and potentially disrupt its electrical activity. Excess weight significantly increases the risk of serious cardiac problems affecting your dog's energy, exercise tolerance, and overall lifespan.
The powerful message is that you can make a real difference . By prioritizing your dog's weight management, you're directly investing in their heart health and future. Talk to your veterinarian about your dog's current weight and discuss a tailored weight management plan if needed.
Follow their recommendations for diet, exercise, and regular monitoring. By working together, we can help your canine companion achieve a healthy weight, leading to a happier, healthier, and longer life with a strong, well-functioning heart.
Dr. Stefan Novevski
Dr. Stefan Novevski is a licensed veterinarian at a small animal clinic specializing in internal medicine, reproduction, dermatology, nutrition, and animal welfare, who continuously updates his expertise through professional development and international clinical experience while prioritizing client education for optimal pet health outcomes.
The information in this article is based on the following scientific publications:
Partington, C., Hodgkiss-Geere, H., Woods, G. R. T., Dukes-McEwan, J., Flanagan, J., Biourge, V. and German, A. J. (2022). The effect of obesity and subsequent weight reduction on cardiac structure and function in dogs. BMC Veterinary Research, 18(1), 351.
Pongkan, W.P. (Wanpitak), Jitnapakarn, W., Phetnoi, W.P. (Warunee), Punyapornwithaya, V. and Boonyapakorn, C. (2020). Obesity-Induced Heart Rate Variability Impairment and Decreased Systolic Function in Obese Male Dogs (1). Animals, 10(8), 1383.
