Sarcopenic obesity is a combination of two disease states, sarcopenia and obesity. Sarcopenia is the muscle mass/strength/physical function loss associated with increased age, and obesity is based on a weight to height ratio or body mass index (BMI) that is characterized by high body fat or being overweight.
The risk of sarcopenic obesity increases with age, and its consequences are a health concern in an ageing population. This condition accelerates muscle mass and function loss as mentioned above, and is a particular concern for the elderly due to its compounding effects on mobility and overall health.
An increased subset of adults over the age of 65 have been classified as having sarcopenic obesity. There is an association between the loss in muscle mass/strength/physical function of sarcopenia and high body fat in obesity as the increased inactivity (sedentary lifestyle) that can occur with a loss in physical function and aging can lead to increase in weight as body fat increases. In regard to sarcopenic obesity prevalence, it is highest among Asian males at 14.4%. Therefore, there is a critical need for a consensus definition for sarcopenic obesity and thus its clinical importance. There is limited additional data among different populations means that future retrospective research studies could clarify statistical data and provide more robust evidence. However, this does not preclude a relationship between the two conditions or dismiss the possibility of associated symptoms and or health complications. These two disease states are synergistic or linked together, as the increase in progression of one disease state increases the severity of the other and vice versa. A Pearson Chi-Square test performed on a sample size of 1637 patients from 2019 to 2021 in community/outpatient clinics at Prince of Wales Hospital determined that Obesity is a risk factor of sarcopenia when obesity is defined as BF% compared to BMI. This can be attributed to high amounts of lean tissue or high muscle mass even though the clinical BMI can be diagnosed as obesity.
Pathogenesis The pathogenesis of sarcopenic obesity involves multiple factors, including aging, lack of physical activity, malnutrition/vitamin imbalances, insulin resistance, and hormonal changes -> body composition changes. The exact pathophysiology is not well understood, however these factors have been studied in the production of sarcopenic obesity. These factors increase ectopic/omental fat deposition, insulin resistance, while decreasing metabolic rate, physical activity, and anabolic hormones. It is thought that GDF15 and FGF21 (protein/cytokine that is biomarker for cell injury/inflammation in response to stress) are increased in sarcopenic obesity. Myostatin is also increased. In the fat, lipotoxicity and chronic inflammation are increased in addition to accumulation of immune cells. In the muscle, mitochondrial dysfunction, oxidative stress (imbalance of free radicals and antioxidants that can lead to cell damage), myosteaosis (fat accumulation in skeletal muscles), and anabolic resistance (reduced stimulation of muscle to amount of protein) can occur. Overall, the cycle of adipose and muscle tissues lead to expansion of white adipose tissue into muscle tissue. This inhibits protein synthesis, resulting in decline of muscle mass and promotes other mechanisms e.g. insulin resistance. The release of cytokines as well inhibits insulin production, and other mechanisms that increase risk of disease e.g. Cardiovascular issues that increase risk of death and decreased life span.
Symptoms The symptoms are similar to those of sarcopenia and obesity. The individual may show a body mass index that is appropriate and healthy to his or her age but will look fat in appearance. People who have sarcopenia are experiencing gradual loss of muscle. This condition commonly presents as reduced endurance, reduced speed while walking, imbalance with increased risk of falls, struggles with everyday activity, difficulty climbing stairs, and loss of muscle size. Sarcopenic obesity also involves obesity. People living with obesity experience an array of symptoms, including difficulty breathing, joint and back pain, a limited ability to participate in physical tasks, snoring, frequently experiencing fatigue, and excessive perspiration. In some patients, a range of comorbidities can coincide with sarcopenic obesity, for example cardiovascular disease, dementia, fractures, diabetes, and even some cancers. In some cases, if a person already has pre-existing conditions, they can worsen if they develop sarcopenic obesity. The effects of obesity are not only physical, people can also have some mental effects. Some of these include, low confidence which can present as doubting ones ability, worry, uncertainty, and being hesitant while assigned or performing tasks. People with obesity also tend to have low self-esteem.
Causes Sarcopenic obesity primarily stems from changes in body composition due to an increase in age, hormonal changes, lack of exercise and a healthy diet, and other diseases.
Aging Aging is the main factor that leads to a change in body composition. These are mainly decreases in muscle strength, increases in total fat mass, and decreases in peripheral subcutaneous fat, all of which can also be attributed to a decline in exercise and reduced basal metabolic rate. Hormonal changes also occur as a person ages, resulting in further changes in muscle composition.
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