Clinical

Sarcopenic obesity: The wasting within


 

Case

The patient is a 65-year-old white female who recently was discovered to have a 2-cm spiculated lung mass in the right upper lobe. She is undergoing an evaluation at present but her main complaint today is that of profound weakness and fatigue. Her appetite and energy level are noticeably less; her family ascribes this to anxiety and depression. Her other medical problems include diabetes, hypertension, osteoporosis, and obesity. The patient believes that she’s lost about 20-25 pounds recently, though her family is skeptical, adding that “she’s been heavy all her life.” Her body mass index is 40. What additional interventions would you add to her workup?

A sign says obesity SandraMatic/Thinkstock

Background

Sarcopenic obesity occurs as a natural consequence of aging. As a general rule, as many as half the women and a quarter of the men over age 80 years are affected. A total of about 18 million people are involved.

One thought as to etiology is that as one ages, proteolysis outdoes protein synthesis. Fat then replaces the body’s muscle, permeates the viscera, and becomes the prominent body form. Chronic lipodeposition leads to chronic inflammation which, in turn, augments protein catabolism. The elderly become less energetic and less active, and the muscle mass decreases further. A vicious cycle develops. Concurrently with obesity, patients suffer with the onset of dyslipidemia, osteoarthritis, osteoporosis (due to vitamin D deficiency), insulin resistance, and an overall increase in frailty.

Sarcopenic obesity also plays a prognostic role in the management of cancer patients where the presence of sarcopenia correlates with earlier death and decreased capacity for therapy. Patients seen as obese are less likely to receive the intensive care (particularly nutritional support) that patients seen as a higher risk receive. The cancer cachexia is less pronounced. The obesity seen externally masks the wasting within.

Dr. Robert Killeen, a physician in Tampa, Fla., who practices internal medicine, hematology, and oncology, and has worked in hospice and hospital medicine.

Dr. Robert Killeen


Diagnosis and treatment

Sarcopenic obesity suffers from an inexact definition. According to the World Health Organization, obesity is defined, officially, as a body mass index of greater than 30 kg/m2. Muscle mass is an important part of this entity, too, but the inclusion of muscle function in this definition brings, seemingly, a point of conjecture. Is muscle function necessary? By what scale do you measure it? This imprecision makes comparative research in the field somewhat more difficult.

As clinical acumen remains the major diagnostic approach to this disease, confirmatory testing for sarcopenic obesity comprises MRIs/CTs and dual energy x-ray absorptiometry (DXA) scans. Presently DXA is used to assess bone density in the diagnosis of osteoporosis. It also reveals the decreased lean appendicular (extremity) muscle mass which, along with the increased BMI, forms the basic diagnosis of sarcopenic obesity. DXA scans are favored over CTs for the assessment of appendicular lean muscle mass. DXA scans provide a relatively inexpensive method of estimating fat, muscle, and additionally, bone density. CTs are less favored because of their radiation exposure as well as their high cost. Assessing muscle strength, using handgrip dynomometry, is available though not widely advocated.

Of the myriad modalities tried in sarcopenic obesity, many have shortcomings. No particular diet format can be advocated. Hypocaloric diets, with or without protein supplementation, offer little advantage to a good physical exercise program. The administration of vitamin D, with calcium, can be of benefit to those sarcopenically obese patients suffering with osteoporosis. Other medications, as exemplified by testosterone, vitamin K, myostatin inhibitors, or mesenchymal stem cells, are either anecdotal or dubious in nature. More research is definitely needed.

The key component for the treatment of sarcopenic obesity is exercise, both aerobic and resistant. Physical exercise recruits muscle satellite cells into the muscle fibers strengthening their composition. Growth factors are also released that stimulate the production of muscle satellite cells. Muscle mass becomes augmented and fortified. Aerobic exercise counteracts the negative metabolic effects of lipids. Resistance training is felt to improve strength when in combination with aerobic exercise, compared with aerobic exercise alone. Research has shown that high-speed resistance training, over a 12-week period, had shown a greater improvement in muscle power and capacity when compared to low-speed training. It was also recommended that patients exercise only until fatigued, not until “failure,” as a stopping point. Programs must be customized to fit the individual.

Sarcopenic obesity is a form of deconditioning that occurs naturally with age but is compounded by cancer. Research into this disease is confounded by a lack of accepted definitions. Radiographic workup and lifestyle changes are the mainstay of medical management. The foremost diagnostic tool remains, as always, clinical suspicion.

Dr. Killeen is a physician in Tampa, Fla. He practices internal medicine, hematology, and oncology, and has worked in hospice and hospital medicine.

Recommended reading

Gruber ES et al. Sarcopenia and Sarcopenic Obesity are independent adverse prognostic factors in resectable pancreatic ductal adenocarcinoma. PLoS One. 2019;14(5): e02115915.10.1371/journal.pone.0215915 [PMID 31059520].

Lombardo M et al. Sarcopenic Obesity: Etiology and lifestyle therapy. Eur Rev Med Pharmacol Sci. 2019; 23: 7152-62.

Petroni M et al. Prevention and treatment of Sarcopenic Obesity in women. Nutrients. 2019; Jun 8.10.3390/nu1161302 [PMID 31181771].

Barcos VE, Arribas L. Sarcopenic Obesity: Hidden muscle wasting and its impact for survival and complications of cancer therapy. Ann Oncol. 2018;29(suppl. 2):ii1-ii9.

Zhang X et al. Association of Sarcopenic Obesity with the risk of all-cause mortality among adults over a broad range of different settings: An update meta-analysis. BMC Geriatr. 2018;19:183-97.

Key points

  • • In sarcopenic obesity a patient’s muscle loss in mass can be clouded, overshadowed by the obese body habitus. The major diagnostic tool initially is clinical suspicion.
  • • The diagnostic tests for sarcopenic obesity are DXA and CT scans.
  • • The best treatment for sarcopenic obesity is a good exercise plan.

Quiz

1. What is the best treatment for sarcopenic obesity?

A. Testosterone

B. Vitamin K

C. Myostatin inhibitors

D. None of the above

Answer: D

There is no particular pharmaceutical treatment, to date, for sarcopenic obesity. Only an exercise program has proved to be of benefit. Those for whom fatigue might be problematic could benefit perhaps by doing “energy banking” or taking programmed naps/rest periods prior to exercise.

2. DXA scans are favored over CT scans because of which of the following?

A. Less cost

B. Capacity to diagnose osteoporosis

C. Less radiation exposure

D. All of the above

Answer: D

DXA scans offer all of the above advantages over CT scans. Also, patients with sarcopenic obesity found to be osteoporotic could be started on vitamin D and calcium supplementation.

3. Which of the following hamper the diagnosis and treatment of sarcopenic obesity?

A. The issue of muscle function

B. Difficulties in comparative research studies

C. Remembering that muscle wasting can occur without external evidence of cachexia

D. All of the above

Answer: D

Obtaining a precise definition of sarcopenic obesity and dealing with the issue of muscle strength and capacity make comparative studies difficult. The sarcopenic obese patient needs as much attention as the cachectic one as their wasting is from within.

4. In sarcopenic obesity and cancer the presence of sarcopenia is likely to lead to which of the following?

A. Earlier death

B. Decreased capacity for therapy

C. Less treatment focus compared to nonsarcopenic patients

D. All of the above

Answer: D

The presence of sarcopenia correlates to all of the above particularly as the obese patient is thought to require less intensive attention than others.

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