In more recent years, nutritionists on the human and veterinary side have started to re-evaluate what we consider a healthy body condition. As CT and MRI scans have become more readily available, we have noticed in both of our patients that while many maintained the same body sizes throughout their lives, they were actually still losing a lot of muscle mass as they aged. It was never obvious on body measurements because the muscle was getting replaced by fat. In some cases, this can be a result of certain diseases and we call this cachexia. However, this can also happen in the absence of disease. In these cases, we call it geriatric sarcopenia. Regardless of the type, loss of muscle mass is universally associated with shorter lifespans in patients.
Normally, when a body isn’t getting its regular nutrients or calories, there can be hormone shifts that allow use of stored fat while sparing muscle mass. However, if those hormone shifts don’t happen, the body will begin to use its own muscle to balance out energy needs. Historically, in veterinary patients, we had recommended lower protein ingestion in dogs and cats. In theory, this should have decreased work on the kidneys and liver while extending livelihood. As we looked into things further, we determined that this is not a universally safe recommendation. This is especially the case with heart disease, kidney failure, and cancer.
In heart disease, there can be shifts in the normal hormones in the body that will start to promote anorexia and muscle burning. We used to restrict protein in these patients but realized they would lose weight more quickly. In kidney disease, we also limited protein so they would not need to work so hard at filtering out the nitrogen leftover when that protein is used by the body. Nowadays, we monitor the body and muscle condition very closely in these patients. In cancer patients, keeping both the appetite and nutrients up has always been a known problem but the reasons for this can vary depending on the cancer.
In sarcopenia, the jury is still out on how to define this condition. Considering what we know now about the diseases I have already mentioned, it is very likely that there are many underlying causes for this general condition. However, as it is typically starting around the same ages, we still watch for it and treat it as an age-related issue.
Diagnosing muscle wasting requires a veterinarian. They are trained in the normal muscle proportions of the body and how to differentiate between causes of the changes in the muscle, such a neurologic disorders, injuries, genetic disorders, etc. When we diagnose one of the diseases mentioned above, we can also do early screening using ultrasound to diagnose early loss and initiate treatment.
While treatment of any known underlying disease is the first thing that we will do, there are nutrition interventions as well. Depending on the suspected underlying cause, veterinarians will pick diets they know to slow progression without negatively affecting other parts of the body. We also will recommend adding Omega 3 fatty acid supplements in the form of certain fish oils or over-the-counter veterinary products. While newer medications are being researched, they are likely very far down the road at this time.