Sarcopenic Obesity

As we discover more all the time, obesity is interconnected with countless other health conditions. It seems impossible to treat this disease in isolation. One related condition gaining attention is sarcopenia—a significant loss of muscle mass. When someone has both a clinically high BMI and sarcopenia, they are said to have sarcopenic obesity (SO). One article called sarcopenic obesity an “emerging public health problem.”

Don’t expect patients to knock down your door asking about it, though. The public may lack awareness of the condition since it hasn’t gripped headlines like, say, type 2 diabetes. (WebMD doesn’t even have an entry for it at the time of this writing.)

It is a serious condition, however, where two interrelated conditions can worsen each other. Excess body weight can make it hard to exercise, which leads to muscle atrophy and less efficient use of calories. Meanwhile, muscle atrophy can also limit a person’s ability to exercise, or even engage in some everyday tasks, leading to weight increase. Becoming versed in sarcopenic obesity can allow you to help people who need medical support to break this vicious cycle.

What is Sarcopenic Obesity?

The World Health Organization defines obesity as, “abnormal or excessive fat accumulation that presents a risk to health.” Currently, diagnosis hinges on BMI (though many consider that measure outdated).

Sarcopenic obesity breaks from some common ideas about obesity and overweight. You may have experience seeing people with obesity who also have significant muscle strength, owing to the body’s need to carry extra weight. Some people also have metabolically healthy obesity; their BMI puts them in the obesity category, but they are not experiencing unhealthy changes in metabolism.

Sarcopenia is defined as the age-associated loss of skeletal muscle mass and function. The causes of sarcopenia are multifactorial and can include disuse, hormonal changes, chronic diseases, inflammation, insulin resistance, and nutritional deficiencies.

The combination of obesity and sarcopenia gives us sarcopenic obesity (SO). In 2022, a panel of international experts defined it in a consensus statement: the co-existence of excess adiposity and low muscle mass/function.

Still, information is lacking. Reporting on the creation of the consensus statement, the journal Clinical Nutrition said:

“Effective prevention and treatment strategies for SO are urgently needed, but efforts are hampered by the lack of a universally established SO definition and diagnostic criteria. Resulting inconsistencies in the literature also negatively affect the ability to define prevalence as well as clinical relevance of SO for negative health outcomes.”

Prevalence numbers for sarcopenic obesity vary by source, but one meta-analysis of 50 studies, representing roughly 86,000 individuals, found a global prevalence of 11% in people over 60. Many cases may remain undiagnosed.

Health Implications of Sarcopenic Obesity

Sarcopenic obesity presents a double metabolic burden. Low muscle mass means less efficient use of calories while excess adipose tissue, as we know, increases the risk of type 2 diabetes, heart disease, and many other health threats. While sarcopenia and obesity each present risks, the combination compounds these.

SO tends to start in middle age or later. Worryingly, it can sneak up on otherwise healthy people. Some muscle loss happens normally with aging—up to 5% per decade after age 30—unless steps are taken to prevent that. Adipose tissue can also “intrude” into muscle, making it less efficient. This is one reason the location of fat, and not just its presence, is gaining attention as an indicator of health risk.

A population-based cohort study dubbed the Rotterdam Study found that SO increases risk for all-cause mortality. The 5,888 participants were 45 years or older with a BMI of at least 27 kg/m² (have overweight but not necessarily obesity). Researchers measured handgrip strength, bone density, and body composition.

5.0% had sarcopenic obesity with one altered component of body composition and 0.8% had sarcopenic obesity with two altered components of body composition. Risk for all-cause mortality was higher among participants with sarcopenic obesity compared with participants without sarcopenic obesity.

In addition to increased mortality risk, individuals with SO may be more likely to develop certain conditions:

Cardiovascular disease

Sarcopenic obesity is linked with cardiovascular disease. It significantly increases the risk of insulin resistance, metabolic syndrome, and adverse glycolipid metabolism. Its impact on metabolic health also raises the risk for atherosclerosis, which itself is related to multiple cardiovascular diseases, and fueled, in part, by insulin resistance. Myocardial fibrosis—scarring of the heart muscle—is also closely associated with SO.

Inflammation

Inflammation is connected with a wide range of health conditions and diseases, not just metabolic ones. However, it is explicitly linked with insulin resistance and, by extension, type 2 diabetes. Obesity, even on its own, predisposes a person to pro-inflammatory states and oxidative stress. The infiltration of adipose tissue into muscle in SO can also lead to atherosclerosis. Inflammation can play the role of both cause and effect in some of these conditions, so it is a factor to watch.

Reduced quality of life and mental health

Less muscle mass and strength can naturally reduce the ability to move freely, harming quality of life. The American Society for Bone and Mineral Research reports that people with sarcopenia (not specifically sarcopenic obesity, however) had 2.3 times the risk of a fall resulting in a low-trauma fracture. This might be a broken hip, collarbone, leg, arm, or wrist, which would impact a person’s ability to conduct daily activities.

Sarcopenic obesity has also been shown to cause osteoarthritis in the knees. Another study reported lower bone mineral density and a higher risk of non-vertebral fracture in older adults with sarcopenic obesity than in adults with obesity only.

Compounding conditions

Further complicating the issue, obesity itself can increase the risk for sarcopenia and vice versa. As you might think, many of the above conditions, from high blood pressure to low bone density, can make it more challenging to exercise. Lack of exercise can worsen the condition.

Contributing Risk Factors

Risk factors for sarcopenic obesity include high caloric intake and/or poor nutrition, especially combined with physical inactivity. Other contributors can include low-grade inflammation, insulin resistance, and hormonal changes. The risk does tend to increase with age, but age is not the only factor.

Biological mechanisms of sarcopenic obesity

SO is marked not only by loss of muscle mass but also by loss of strength and changes in muscle composition. Hormones affect how muscles respond to aging in both men and women. After menopause, a decline in estrogen tends to cause fat to shift to visceral deposits, often in the form of belly fat. Declining testosterone can reduce muscle strength and increase the ratio of fat to muscle. Both scenarios are conducive to sarcopenic obesity.

Muscle tissue itself relies on protein synthesis. When muscle degrades faster than it can rebuild, it moves in the direction of sarcopenia. Diet and nutrition may play a role here, as sufficient protein becomes critical.

With age, adipose cells can increase in size and secrete more adipokines such as leptin, chemerin, and resistin, as well as more cytokines such as tumor necrosis factor-α (TNF-α), interleukins (ILs), and interferon-γ (INF-γ). These conditions set the stage for inflammation, which starts another SO cycle. Studies indicate that an inflammatory state plays a significant role in the progression of SO as well as the morbidity and mortality driven by SO.

Diagnostic Criteria and Measurement

The signs of sarcopenic obesity emerge gradually and can be mistaken for “normal aging,” which makes it sometimes fly under the radar. Researchers are seeking a biomarker that could be detected using a low-cost lab test, but other methods must suffice for now.

Diagnosis hinges on obesity, currently measured by BMI, and the presence of sarcopenia. Sarcopenia itself is measured by both muscle mass and muscle function. In 2010, the European Working Group for the Study of Sarcopenia stated that both were required for diagnosis. Their reasoning is that the relationship between strength and mass is bidirectional. They also consider gait speed, looking for a speed of less than 0.8 m/s to diagnose.

The next question, then, is how to measure muscle mass and strength. CT scans and MRIs can be used to observe and compare the amount of fat tissue and muscle mass. However, these methods come with a high cost and are often impractical. DXA provides a less expensive option for estimating muscle versus fat content in the body.

Handgrip strength is typically used to test muscle strength, as it can predict extremity muscle power and mobility. Knee flexion and extension may also provide a measurement of strength and insights into a person’s ability to move and function. Physical performance can be measured with the short physical performance battery (SPPB), which evaluates lower extremity functioning in older people. Other potentially useful measurements include gait speed, timed get-up-and-go test, and stair climb power test.

A variety of data must be collected and considered together in order to arrive at a diagnosis of sarcopenic obesity.

Treating Sarcopenic Obesity

Since it lies at the intersection of so many interrelated conditions, a patient’s care team might include an obesity specialist, a geriatrician, a nutritionist, and/or a physical therapist. Comorbidities can draw in still more specialties, perhaps oncology or endocrinology. Good communication among different healthcare providers can make a positive difference in the patient’s progress.

One may treat sarcopenic obesity much the same as obesity alone, with a few caveats. One, of course, is understanding that low muscle mass and strength may present challenges for exercise.

Exercise

Some of the best practices for obesity and exercise[1] include finding activities that a person can do comfortably, consistently, and safely. Within those parameters, it’s important to combine aerobic activity, strength training, and exercises that build flexibility and balance. For people not yet diagnosed with SO, but at risk for it, exercise can help prevent this condition.

Nutrition

Developing a diet for a person with SO presents a paradox. When anyone restricts calories, they risk losing muscle. This is especially true for adults with obesity, in whom an estimated 25% of the weight loss achieved by cutting calories is skeletal muscle mass.

It’s critical to optimize nutrient intake to increase skeletal muscle mass (or at least prevent loss) while also aiming to decrease excess fat mass. Protein and amino acids can make a difference.

A recommended dietary protein intake is 1.0 to 1.2 g/kg BW to maintain and regain muscle mass and function in people over 65. Another recommendation is to combine anabolic nutrients, such as protein, amino acids, vitamin D, and omega 3. In observational studies, minerals such as magnesium, selenium, and calcium also seem effective at building and maintaining muscle.

Medications and Surgery

Another point to remember with SO is that rapid weight loss carries the risk of muscle loss and bone density. For that reason, patients with SO who are prescribed anti-obesity medication need to be monitored closely with the goal of not exceeding 2lb loss per week in order to avoid further muscle loss.

Since sarcopenic obesity is often seen in older adults, consideration for their age must play a role. While a variety of weight loss medications are approved for ages 12 and up, that does not make them a good choice for every adult at every age. With GLP-1s, the gastrointestinal side effects, which can happen to anyone, tend to be worse in older age. Bariatric surgery requirements generally state that a patient should be aged 18-65 and free of certain comorbidities.

For younger people with sarcopenic obesity, medications or surgery might be considered, but with careful attention to nutrition and other health conditions.

Watch Out for Sarcopenic Obesity, Especially in Older Patients

When treating patients with overweight and obesity, especially older adults, it’s important to be aware of sarcopenic obesity. Your intervention might help people to understand, prevent, and even overcome this complicated condition. To learn more about this condition, watch our webinar on “Sarcopenic Obesity and Its Implications.” You can also gain access to other relevant resources by becoming an OMA member.

Noting that this blog post has not been updated to the version we wrote in October