Obesity and epigenetics
One of the most important health problems in veterinary medicine today is the epidemic of obesity in our pets. Just as in humans, chronic consumption of excess calories leads to overweight and obesity in dogs, and to the many health problems that follow. Most pet parents are aware that it is unhealthy for dogs to be overweight, but food is one of the major ways we have of expressing our love for our pets, so it is difficult to deny our dogs their treats even when we know we are overdoing it.
Many pet owners may not realize, though, that overfeeding and obesity may age our dogs prematurely. Fat is not just a quiet storage place for excess calories. It is a very metabolically active tissue that can influence the function of cells and organs throughout the body. Changes in metabolism with excess body fat are very similar to the changes seen with aging. Most of the research on this has been done in humans or rodents, but it is likely the biology of obesity and aging in dogs is very similar to humans, as it is for aging in general.
The underlying changes in the cells and tissues of the body that lead to the physical and functional manifestations of aging are many and complex. Some of these are:
Oxidative stress- this is an increase in reactive chemicals that can damage cells and DNA.
Shortened telomeres- telomere shortening can reduce the lifespan of cells.
Epigenetic changes- these are changes in the structure of DNA that can impact how our genes are turned on and off (take a look at this previous post for more information)
Faulty “zombie” cells- cells that undergo a process called senescence (so-called “zombie” cells) lose their normal functions and instead start producing substances that damage other cells and speed up aging.
Faulty mitochondria- these little power plants in the cell drive all the activities of metabolism, and when they are damaged by aging or obesity, the animal can literally run out of energy!
Faulty proteins- proteins make up most of the structure of our bodies, and when damaged by age or obesity, they can lead to disease, especially degenerative brain diseases like Alzheimer’s.
Inflammation- while some inflammation is good, helping us fight infections, too much can cause harm. This happens with both aging and obesity.
Faulty tissue repair & regeneration- as we age, we lose our capacity to rebuild and repair tissues as they wear out or get injured. This contributes to loss of normal function in the elderly and the obese.
Faulty immune function- our immune systems get weaker with age, making us more vulnerable to infection, and this happens with obesity as well
Key mechanisms of aging in dogs.
In humans, it is well demonstrated that these underlying changes, in both aging and obesity, lead to physical and functional decline and ultimately disease and death. The most common diseases of aging, such as cardiovascular disease, diabetes, and cancer, all happen earlier and more often in people who are significantly overweight. People suffering from obesity also have generally shorter life expectancy—as much as 6-7 years shorter by some estimates.
The image below, from a recent review article called Aging and obesity: Two sides of the same coin, illustrates how obesity both shortens lifespan and leads to earlier onset of chronic disease and disability. Being overweight is, of course, only one possible risk factor for these problems, and the risks increase even more when others are added, such as smoking or a lack of physical activity. However, obesity is unique in that it raises our risk of health problems and death by mechanisms that look very much like those at work in normal aging.
How overweight and obesity reduce lifespan and increase disease. From Tam BT, Morais JA, Santosa S. Obesity and ageing: Two sides of the same coin. Obes Rev. 2020;21(4):e12991.
There is less research in dogs than humans specifically comparing the mechanisms of obesity and aging that cause disease and death. We do know that overweight dogs die younger than those with normal body condition, anywhere from 6 months to over 2 years younger, depending on the breed.
We also know that obese dogs have an increased risk of at least some diseases typically associated with aging, such as cancer, diabetes, kidney disease, heart disease, and arthritis. The exact impact of obesity on these risks in various breeds is not yet known, but the limited information we have so far suggests a very similar pattern to that seen in humans.
Finally, we also know that many of the same underlying mechanisms of aging are active in obese dogs, including oxidative stress, inflammation, and epigenetic changes. A deeper understanding of how the processes of aging and obesity are related in dogs will require more research. However, what we already know is sufficient to recognize that obesity is a serious health risk for dogs, and it very likely increase the risk of disease and death by accelerating processes that are also part of normal aging. By overfeeding our dogs, we may actually cause them to age faster!
The good news is that this is something we have control over! There is lots of evidence that reduced feeding, and possibly increased physical activity, can prevent and treat obesity in dogs and take away this extra threat to their health. There is even research showing that more aggressive restriction of calories can slow aging and extend lifespan and healthspan, so long as we do not go so far as to cause malnutrition. Finding ways other than food to show love to our pets, such as play and walks or just cuddle time, can reduce the risk of obesity and may slow down the aging of our beloved canine friends.
Learn More
Here are some scientific articles discussing the relationship between obesity and aging as well as reviewing some of the underlying mechanisms for both.
Tam BT, Morais JA, Santosa S. Obesity and ageing: Two sides of the same coin. Obes Rev. 2020;21(4):e12991. doi:10.1111/OBR.12991
Salvestrini V, Sell C, Lorenzini A. Obesity May Accelerate the Aging Process. Front Endocrinol (Lausanne). 2019;10:266. Published 2019 May 3. doi:10.3389/fendo.2019.00266
McKenzie, BA. Key Aging Processes and Critical Knowledge Gaps in Veterinary Geroscience. (2022) Amer J Vet Res
López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G. The hallmarks of aging. Cell. 2013;153(6):1194-1217.
Sándor S, Kubinyi E. Genetic Pathways of Aging and Their Relevance in the Dog as a Natural Model of Human Aging. Front Genet. 2019;10:948.