Q: I am looking for guidance on how to support muscle/weight loss in an almost 16-year-old cat with stage II chronic kidney disease (CKD). He’s been slowly dropping muscle mass and then dropped a bigger amount in the last few months. He acts normal, plays fetch, and retrieves his toys from around the house. He purrs and wants to be close by.
We feed him both wet and dry renal diets. Are there any supplements I can give him to counteract the weight and muscle loss?
A: Thanks for getting in touch about this common problem in aging cats and cats with CKD. Cachexia, or the loss of lean body mass (LBM), is found in many cats that suffer from chronic diseases, including CKD. Sarcopenia also refers to the loss of LBM, but this term is used to describe the age-associated loss of LBM that occurs in the absence of disease.
It is quite possible, if not probable, that your kitty is experiencing both cachexia (due to his CKD) and sarcopenia (due to his age), and perhaps a few highlights of these conditions and how to address them would be helpful.
In a healthy cat who is consuming insufficient dietary calories, fat stores are metabolized to provide energy required for life, sparing the loss of lean muscle.
In cats with cachexia, abnormalities of metabolism mediated by a change in the activity of a variety of compounds, including chemicals released by inflammatory cells (cytokines), cortisol (a stress hormone), and insulin, prevent the use of fat stores when caloric intake is insufficient, and muscles begin to be metabolized to provide energy (leading to a decrease in muscle mass).
This process is compounded by the fact that many diseases cause an increase in metabolic rate and, therefore, caloric requirements for daily living.
Sarcopenia also results in loss of LBM, but this loss is a normal age-associated change in cats (and other mammals, including dogs and people). It is likely mediated by a combination of decreased activity, decreased secretion of growth hormone and testosterone, changes in the types of muscle fibers produced, decreased protein synthesis, increased cytokine production, and insulin resistance. Often, sarcopenia is accompanied by an increase in body fat, so while an individual experiencing sarcopenia’s weight might not change, their muscle mass will decrease. Both cachexia and sarcopenia are compounded by decreased food intake and decreased absorption of nutrients from the GI tract.
Interventions that are commonly undertaken to combat both cachexia and sarcopenia include assurance of adequate caloric intake by assuring that foods are palatable, that foods are nutritionally complete and balanced and of sufficient caloric density, that there are no addressable problems that negatively impact food intake (like dental disease), and the use of appetite stimulants.
Omega-3 fatty acid supplementation may benefit both cachexic and sarcopenic cats. Encouraging cats suffering from decreased LBM to exercise regularly can also be beneficial.
In the case of cats with CKD, in which dietary protein restriction is important to decrease the workload on kidneys, finding the right balance of protein restriction and the provision of sufficient high quality digestible protein to maintain lean muscle mass is important, and this is a major goal in the development of renal diets for cats.
I hope this is helpful, and please continue to work closely with your veterinarian to develop an optimal feeding/treatment plan for your boy.
