Overview
Obesity is a widespread medical condition that affects millions of people. Individuals with obesity have an increased risk of developing various comorbidities, including diabetes, heart disease, hypertension, osteoarthritis, sleep apnea, etc. However, obesity has not yet gained sufficient attention as a debilitating disease that affects the human body from within.
But what if a patient develops another equally devastating condition that further escalates obesity and creates a vicious cycle of illness, inability to recover, and exacerbation?
Sarcopenic obesity is the loss of muscle mass, strength, and functions on the foundation of obesity and can lead to serious health complications.
While this concurrence of diseases is often ignored and underappreciated, its prevalence is shockingly high. For example, according to a 2021 study by Frontiers in Physiology, sarcopenic obesity can occur in up to 85.3% of males and 80.4% of females.
This article discusses the detrimental impact of sarcopenic obesity, its symptoms, the culprits behind this double layer of disease, and the currently available approaches to treating and managing sarcopenic obesity.
Sarcopenic Obesity: A Vicious Cycle of Weight Gain and Muscle Loss
What Is Sarcopenic Obesity?
Definition
According to Karger Research, sarcopenic obesity is characterized by the coexistence of sarcopenia – a disease that causes low muscle mass – and high body fat percentage, particularly in the abdominal region. This condition has been identified as a geriatric syndrome with a complex etiology, and its prevalence increases with age.
The term “sarcopenia,” which derives from the Greek words “sarx” (meaning “flesh”) and “penia” (meaning “loss”), originally referred to the age-related decrease of muscle mass. Today’s consented definition refers to sarcopenic obesity as having an amount of lean mass lower than average relative to the existing amount of fat mass.
Typically, in healthy young and older people, bones and muscles grow harmoniously with increased body weight. In other words, if you gain weight, your bones and muscles grow and become stronger. However, in those with sarcopenic obesity, weight gain occurs without a parallel increase in either muscle mass or strength.
Diagnosis
Diagnosing sarcopenic obesity requires the assessment of several parameters, including:
- Loss of muscle mass
- Fat distribution
- Waist circumference
- Body mass index (BMI)
The percentage of muscle loss is measured by analyzing a person’s skeletal muscle mass index (SMI), calculated by dividing muscle mass by height squared. A low SMI indicates a loss of muscle mass, a characteristic of sarcopenic obesity.
In addition to muscle loss, identifying the percentage of increased body fat also helps determine the condition. This parameter is measured using dual-energy X-ray absorptiometry (DXA) or bioelectrical impedance analysis (BIA).
Waist circumference is another critical parameter used to diagnose sarcopenic obesity. A waist circumference greater than 102 cm in men or 88 cm in women indicates abdominal obesity, associated with an increased risk of chronic diseases.
BMI is often the most useful diagnostic criterion. A BMI greater than 30 kg/m2 indicates obesity, which, combined with muscle loss, suggests sarcopenic obesity.
What Are the Symptoms of Sarcopenic Obesity?
Sarcopenic obesity symptoms can vary depending on each individual. Some people experience mild symptoms, while others are more severe and debilitating.
The combination of sarcopenia and obesity can make it difficult to differentiate between symptoms specifically related to one condition versus the other. Therefore, a thorough evaluation is necessary to diagnose sarcopenic obesity accurately.
Sarcopenia-related Symptoms
- Decreased muscle strength and endurance
- Reduced mobility and physical function
- Fatigue and weakness
- Difficulty performing daily activities
- Poor balance and coordination
- Slower walking speed
- Increased risk of falls and fractures
Obesity-related Symptoms
- Increased body fat, particularly in the abdominal region
- High blood sugar levels or insulin resistance
- Elevated cholesterol and triglyceride levels
- Elevated blood pressure
- Cardiovascular disease
- Type 2 diabetes
- Sleep apnea and other breathing problems
- Joint pain and reduced range of motion
- Increased risk of certain cancers
What Causes Sarcopenic Obesity?
Excess Energy Intake and Inactivity
The first cause of sarcopenic obesity is excess energy intake and inactivity. Today’s society is bombarded with highly processed, calorie-dense foods that are low in nutrients. Amplified by sedentary lifestyles, this extra energy intake can lead to obesity and muscle loss.
According to the World Health Organization (WHO), over 1.9 billion people were overweight in 2016, with over 650 million classified as obese. Also, the Global Health Observatory (GHO) shows that physical inactivity is responsible for around 3.2 million deaths annually.
Adipose Tissue Derangements
The second likely cause of sarcopenic obesity is adipose tissue derangements. Adipose tissue, or body fat, is a passive storage depot for excess energy and an active endocrine organ that produces hormones.
In obesity, adipose tissue becomes dysfunctional, leading to low-grade chronic inflammation and insulin resistance. These factors can negatively impact muscle metabolism, further exacerbating sarcopenia.
According to a study by the Journal of Physiology, leptin – a hormone released by adipose tissue – plays a vital role in muscle metabolism. Therefore, individuals with adipose tissue dysfunction may experience a loss in muscle mass and strength.
Muscle Metabolism Diseases
Muscle metabolism diseases can include genetic disorders such as muscular dystrophy or acquired conditions such as skeletal muscle dysfunction due to chronic obstructive pulmonary disease (COPD) or cancer cachexia.
According to a study by the Journal of Cachexia, Sarcopenia, and Muscle, cancer cachexia alone affects up to 80% of advanced cancer patients, significantly impacting muscle mass and function in a phenomenon known as muscle wasting.
These conditions can result in an impaired balance between protein synthesis and degradation, a breakdown of muscle tissue, and decreased muscle size and number.
Age-related Muscle Loss
The last possible cause of sarcopenic obesity is age-related muscle loss. Our bodies undergo numerous changes as we age, including decreased muscle mass and function. This phenomenon is then further exacerbated by a sedentary lifestyle and poor nutrition.
According to the same study by the Journal of Cachexia, Sarcopenia, and Muscle, the prevalence of sarcopenia increases with age, from 15% at 65 to 50% at 80 years old. Beyond 50, natural aging is associated with 1-2% annual muscle loss. Also, at age 70, muscles have lost 40% of their strength and 30% of their size.
How Does Sarcopenic Obesity Affect Longevity?
Increase Mortality Risks
According to a study published in BMC Geriatrics, individuals with sarcopenic obesity have a significantly higher risk of all-cause mortality than those without the disease, even after adjusting for confounding factors such as age, sex, and lifestyle habits.
Specifically, sarcopenic obesity patients have a 1.21-fold risk of all-cause mortality compared to non-sarcopenic non-obese, with hospitalized patients having a higher probability.
The study also concluded the mechanisms behind the link. The symptoms of sarcopenia, such as reduced muscle mass, inflammation, and insulin resistance, raise the risk of death. Low muscle mass may be the most critical aspect of all. Also, low muscle mass or poor physical performance are additional risk factors for fatal falls and fractures.
Exacerbate Comorbidities
Sarcopenic obesity can exacerbate underlying comorbidities in patients, primarily related to metabolic and cardiovascular health.
Individuals with sarcopenic obesity tend to have a higher prevalence of conditions such as diabetes, heart disease, hypertension, osteoarthritis, and sleep apnea. These conditions often require lifestyle interventions, including increasing physical activity and inducing weight loss, to manage symptoms and prevent further complications.
However, decreased muscle mass and strength can prevent patients from implementing these interventions. This challenge can create a frustrating cycle in which weight gain and muscle loss perpetuate each other, leaving patients positioned further from treatment.
Moreover, the lack of physical activity and exercise can lead to a further decline in muscle mass, worsening the symptoms of sarcopenic obesity and making it even more difficult for patients to manage their comorbidities.
How to Treat Sarcopenic Obesity
Lifestyle Interventions
According to the Journal of Current Opinion in Endocrinology, Diabetes, and Obesity, a combination of weight loss, exercise, and nutritional modification is the optimal treatment for sarcopenic obesity.
Weight Loss
The study found that although a 20% reduction in body weight (from 95 to 75 kg) resulted in a loss of fat mass (30%) and lean mass (10%), the proportion between the 2 parameters was justifiable and led to a significant improvement in sarcopenia.
It is crucial to remember that a modest reduction in lean mass following this intervention does not imply an exacerbation of sarcopenia because the amount of lean mass is now higher than before in relation to fat mass.
Combined Weight Loss and Exercise
Notably, if the patients implement an exercise regimen called Progressive Resistance Training (PRT), the improvement in sarcopenia would be even more significant. This intervention is characterized by 3 sessions per week (90 minutes each) consisting of flexibility, low-impact aerobic, high-intensity resistance, and balance training.
After completing the PRT, the study found a 10% reduction in body weight, an 18% loss in fat mass, and a 4% gain in lean mass. These results suggest weight loss and exercise are the most effective interventions for sarcopenic obesity.
Nutritional Modification
Research shows that older adults need more protein than younger adults to maintain the same amount of muscle mass and prevent sarcopenia.
As a result, scientists recommend that older people consume 25-30 grams of protein at each meal to prevent sarcopenia. This recommendation is based on data showing that those consuming less than this amount have suboptimal muscle protein synthesis.
In addition, a moderately low-carb diet may also be beneficial since ingesting carbs can negatively impact protein synthesis in older adults.
Leucine, the most effective amino acid for protein synthesis, can also be a supplement for preventing sarcopenia. For example, leucine supplementation, independent of other amino acid use, can improve muscle protein synthesis in older adults.
Pharmacologic Therapy
Although lifestyle interventions are a cornerstone of managing sarcopenic obesity, not all patients can implement these measures due to physical limitations or poor adherence. As a result, pharmacologic treatments are becoming increasingly popular.
Myostatin Inhibitors
One of the most promising pharmacologic approaches to managing sarcopenic obesity is inhibiting myostatin in the human body.
Myostatin, produced by muscles and fat, is a growth factor that negatively affects lean mass and body composition. Research has shown that administering myostatin to animals resulted in muscle loss. Also, myostatin is a biomarker of age-related sarcopenia, negatively correlated with muscle mass, with greater levels seen in frail older adults.
Therefore, myostatin inhibitors have recently gained popularity as candidates for improving lean mass, increasing muscle strength, and reducing fat mass in sarcopenic obesity.
Indeed, early research and observations in animals whose myostatin is removed or deficient suggest that myostatin inhibition results in the following:
- Improved muscle mass and function
- Favorable changes in adipose tissue
- Reduced inflammatory markers
- Enhanced thermogenesis
- Protection against sarcopenia
- Resistance to obesity
Nevertheless, despite numerous animal studies, clinical evidence in human patients is scarce. Past studies only focus on using myostatin inhibitors in treating muscular dystrophy, not sarcopenic obesity.
Accordingly, studies show myostatin inhibition increases cellular muscle function in individuals with muscular dystrophy. Yet, they found no quantifiable improvements in muscle strength. This finding is consistent with other animal studies, where an absence of myostatin reduced muscular energy despite increased muscle mass.
Testosterone Therapy
Clinical evidence shows that testosterone therapy can increase muscle mass and improve body composition in individuals with sarcopenic obesity.
Testosterone is essential for maintaining muscle mass and strength, with levels declining with age. Testosterone therapy can help to restore these levels, leading to an improvement in muscle mass and strength.
A 12-month study on testosterone therapy in healthy older adults prescribed to regular exercise found an improvement in body composition and an increased upper body strength, yet noticed no gains in physical function. Similarly, a 4-week study on testosterone therapy in 6 healthy older men found improved hamstring and quadriceps strength.
However, higher testosterone doses may result in more frequent adverse effects. Therefore, it is vital to note that testosterone therapy should only be used under supervision after carefully considering the potential risks and benefits.
References
Bouchonville M. et al. (2013). Sarcopenic Obesity – How Do We Treat It? Journal of Current Opinion in Endocrinology, Diabetes, and Obesity.
Bowen T. et al. (2015). Skeletal Muscle Wasting in Cachexia and Sarcopenia: Molecular Pathophysiology and Impact of Exercise Training. Journal of Cachexia, Sarcopenia, and Muscle.
Jaitovich A. et al. (2018). Skeletal Muscle Dysfunction in Chronic Obstructive Pulmonary Disease. The American Journal of Respiratory and Critical Care Medicine.
Zhang X. et al. (2019). Association of Sarcopenic Obesity With the Risk of All-cause Mortality Among Adults Over a Broad Range of Different Settings: an Updated Meta-analysis. BMC Geriatrics.
Purcell S. et al. (2021). Prevalence of Sarcopenic Obesity Using Different Definitions and the Relationship With Strength and Physical Performance in the Canadian Longitudinal Study of Aging. Frontiers in Physiology.
Donini L. et al. (2022). Definition and Diagnostic Criteria for Sarcopenic Obesity: ESPEN and EASO Consensus Statement. Karger Research.
Collins K. et al. (2022). Leptin in the Regulation of Muscle Mass and Strength by Adipose Tissue. The Journal of Physiology.
If you have questions about sarcopenic obesity or any health problems discussed here, connect with us and learn more.
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