When it comes to human weight and its effect on lifespan, opinions change about as often as the latest fad diet. One reason it’s difficult to pin down an answer is that people live such long lives that it’s difficult to study humans across an entire lifespan.
With dogs, it’s different — the average dog lifespan is considerably less than a human’s. Labrador retrievers, for example, have an average lifespan of 10 to 12 years. That’s why researchers were able to conduct a groundbreaking, 14-year study following 48 Labrador retrievers throughout their entire lives to discover that keeping dogs lean can add, on average, almost 2 years to their lifespans.1
Tracking Dog Life Expectancy
The study started with 48 Labrador retriever puppies. All dogs received the same diet, but half of the dogs were fed 25 percent less food than the other dogs. Even though some dogs received less food, researchers made sure the group wasn’t missing any nutrition.
At the end of the study, the median lifespan for dogs who ate less was 13 years, compared to 11.2 for the dogs that were fed more — that’s a difference of 1.8 years. It was the first longitudinal study to show that dietary restriction, without malnutrition, could extend dog lifespan.
Overweight Dogs and Other Health Conditions
Life expectancy isn’t the only factor that excess weight gain impacts. Feeding restriction didn’t have a negative impact on these large breed dogs in terms of how their skeletons matured, bone structure or metabolism,2 but dogs that were kept lean experienced joint-health advantages.
By two years of age, the incidence of hip dysplasia in the dogs fed less was half that of the full-fed dogs. The severity of the condition was much less for the lean dogs, as well.3
The onset of hip arthritis for these dogs was later in life, too. The median age when hip arthritis could be recognized on X-rays was 6 years for the full-fed dogs, while dogs with lower body weight didn’t show evidence of arthritis until 12 years of age. That’s six extra years of chasing balls and going on hikes, presumably without the pain of arthritis to hold them back.
The same was true for arthritis in other joints. At 8 years of age, only 10 percent of lean dogs had osteoarthritis in two or more types of joints, compared to 77 percent of the full-fed dogs.4
Other Healthy Weight Benefits
As dogs age, they have a higher risk of suffering from age-related diseases. Compared to the full-fed dogs, lean dogs showed greater insulin sensitivity, which helps stave off diabetes. Their immune systems were better able to fight off infections, as well. This could be part of the reason why keeping dogs lean seems to delay the onset of age-related diseases. The mean age at which half of the lean dogs required treatment for a chronic condition was 12 years of age, compared to 9.9 years for the full-fed dogs.1-3
Other research that analyzed breeds other than Labradors has found similar results: reduced risks of certain health issues correlated with the dog’s weight, with small dogs showing increased risk of shorter lifespans than larger dog breeds (although excess body weight was a negative for all breeds).5 Veterinary medicine has made strides in all areas of dogs’ health, but dog owners still make a major contribution when they help their furry friend maintain ideal body weight.
Dog Years of Good Health
For pet parents with overweight dogs, the lesson from these studies is this: weight loss can help improve their health, delay the onset of some medical conditions, improve quality of life and even extend their old age. That said, you shouldn’t just reduce the quantity of your dog’s food by 25 percent, because that can lead to nutritional inadequacies. Instead, work with your veterinarian to devise a healthy weight-loss plan — and the plan to help your dog stay in that healthy body condition.
Start by assessing your dog’s current body condition. Are they considered overweight now? This is not just a number: look to see if, for example, you can see your dog’s ribs or whether they are masked by extra body fat. Consult your veterinarian to determine your dog’s healthy weight and tips on a plan to lose weight if necessary. Reaching that ideal body condition could take a mix of exercise and changing food intake.
Especially if your dog hasn’t been doing much physical activity up to now, your veterinarian’s advice is a good first step to the new exercise plan — you want to be sure other factors are taken into consideration, as well as weight or obesity.
An advantage of this care and attention to the well-being of our pets? Perhaps improved wellness and a healthier life for their human. We’ll be getting more exercise alongside them, and when our dogs live longer, we live happier.
References
- Kealy RD, Lawler DF, Ballam JM, et al. Effects of diet restriction on life span and age-related changes in dogs. J Am Vet Med Assoc 2002; 220:1315–1320.
- Lawler DF, Larson BT, Ballam JM, et al. Diet restriction and ageing in the dog: major observations over two decades. Brit J Nutr 2008; 99(4):793–805.
- Smith GK, Paster ER, Powers MY, et al. Lifelong diet restriction and radiographic evidence of osteoarthritis of the hip joint in dogs. J Am Vet Med Assoc 2006; 229(5):690–693.
- Kealy RD, Lawler DF, Ballam JM, et al. Evaluation of the effect of limited food consumption on radiographic evidence of osteoarthritis in dogs. J Am Vet Med Assoc 2000; 217(11):1678–1680.
- Salt C, Morris PJ, Wilson D, et al. Association between life span and body condition in neutered client-owned dogs. J Vet Intern Med 2018; 33(1):89–99.
