Sarcopenic obesity could lead to adverse health outcomes in the elderly.

As we age, our body composition naturally changes. For example, we are more likely to gain weight and lose muscle mass, and the distribution of fat mass across our body changes.¹ While obesity is on the rise among younger members of the population, it is also on the rise in the elderly. Specifically, for aging adults, sarcopenic obesity is on the rise.² While there is still no consensus on the definition of sarcopenic obesity, we do know that it is characterized by low muscle mass and excess fat mass.^1,2 Sarcopenic obesity was previously defined as a muscle weakness.¹ Despite the lack of consensus, health care professionals are aligned in their perception that sarcopenic obesity represents a risk for adverse health outcomes in the elderly.

Understanding Sarcopenic Obesity

Researchers recognize the complicated etiology of sarcopenia. Sarcopenia was initially believed to be characterized by a measurable difference between fat mass and muscle mass.¹ For example, patients were considered sarcopenic when their BMI was > 30 or a dual-energy X-ray absorpitometry (DXA) was within -1 and -2 standard deviation of young same sex reference group; e.g., -1 or -2 with a comparison group of younger women and elderly women or younger men and elderly men.³ Sarcopenic obesity was also believed to be associated with hormonal changes that emerge as we age, chronic low-grade inflammation, insulin resistance, little physical activity, and poor diet.² More recent definitions of sarcopenia suggest a consideration of muscle impairment instead of muscle mass. Dynapenic abdominal obesity (DAO) is understood as a large waist circumference and low grip strength.² Despite the lack of consensus around definitions of sarcopenic obesity, there is agreement around some of the metrics and the negative health outcomes.

Age, Hormones and Inflammation

As we age, we experience changes in our hormone levels, and these changes affect body composition through weight gain.² Total fat mass has been reported to peak between ages 60-75 while muscle strength begins to decline around age 30.² As we age, there is a negative correlation between muscle strength and fat mass, such that in the elderly, body weight is comprised primarily of adipose tissue.

Insulin resistance is also a function of aging as well as decreases in thyroid hormone levels and increases in cortisol levels. Changes to insulin-like growth factor (IGF-1), sex hormones, and dehydroisoandrosterone sulfate are also implicated in sarcopenic obesity. For example, postmenopausal women experience increases in adipose tissue and visceral fat as skeletal muscle mass decreases. With respect to men, they experience declines in testosterone and changes in the distribution of adipose tissue and muscle.²

Sarcopenic obesity has also been implicated in chronic inflammatory state that negative affects metabolic functioning and increases one’s risk of chronic disease.² Adipocytes have been found to accumulate in the heart, liver, and pancreas as well as muscle. These accumulations prompt secretions of proinflammatory cytokines such as TNF-α, IL-6, IL-1, and leptin, thereby allowing inflammatory cells to infiltrate and induce insulin resistance and lipotoxity. This negatively affects skeletal muscle mass and speeds up muscle degradation. Leptin increases IL-6 and TNF, which in turn reduce anabolism while decreases in IGF-1 and loss of testosterone associated with age increases frailty.²

Negative Health Consequences of Sarcopenic Obesity

As fat mass increases and muscle mass decreases with age, one’s risk of mortality, cardiovascular disease, and disability increase.¹ For example, a National Health and Nutrition Examination Survey (NHANES),⁴ found that for those aged 50-70, sarcopenic obesity increased the risk of mortality. Interestingly, those 70 and older did not have an increased mortality risk.

A 2018 study⁵ found that handgrip strength, a measure of muscle quality, was associated with sarcopenic obesity and mortality. When sarcopenic obesity was defined as waist circumference, men with larger waist circumferences experienced more all-cause mortality.¹ Disabilities (e.g., cognition) were also found to worsen when dynapenic abdominal obesity (DAO) was present. Although only a handful of studies investigated cardiovascular disease, a relationship between sarcopenic obesity was found.¹

Prevention and Treatment of Sarcopenic Obesity

To date, there is no known optimal treatment for sarcopenic obesity. However, nutrition and diet interventions and exercise are promising.² Extreme caloric restrictions in elderly adults are strongly advised against due to the risks of skeletal muscle mass loss, bone mineral density, and electrolyte disorders. Instead, more moderate caloric restriction is advised (200-750 kcal per day).¹ Dietary recommendations for elderly patients with sarcopenic obesity include increases in high quality protein consumption (1.2 -1.5 g/kg/d). For elderly patients with sarcopenic obesity and chronic disease or compromised renal health, protein intake should be closely monitored. Essential amino acids and high leucine content should also be considered because they promote muscle protein synthesis. Vitamin D and calcium should also be considered as part of a dietary intervention.¹

Physical activity such as aerobic exercise and resistance training are also effective strategies for mitigating the risks of sarcopenic obesity. Aerobic exercise can improve a patient’s cardiovascular fitness and resistance training can help enhance muscle mass.¹ Any exercise program should be undertaken with the supervision of a patient’s health care provider to ensure the program is tailored to that person’s specific needs.

Although sarcopenic obesity increases with age, there are steps health care professionals can take to mitigate its negative effects. As noted above, dietary and exercise interventions can help. Working with elderly patients with sarcopenic obesity to develop a nutrition and exercise program that meets their specific needs is a good first step. While consensus is lacking around what sarcopenic obesity is, we do know that there are negative health consequences for elderly patients who have more fat mass than muscle mass. It is important for health care professionals to recognize the risks and work with their patients on a supervised plan to mitigate the associated risks.

Sources:

1. Sarcopenic obesity: An emerging public health problem
2. Sarcopenia and obesity 
3. Sarcopenic obesity: A new category of obesity in the elderly
4. Sarcopenic obesity and overall mortality: Results from the application of novel models of body composition phenotypes to the National Health and Nutrition Examination Survey 1999–2004
5. Association of sarcopenic obesity predicted by anthropometric measurements and 24-y all-cause mortality in elderly men: The Kuakini Honolulu Heart Program