Sarcopenic obesity in older adults: aetiology, epidemiology and treatment strategies

Abstract

The prevalence of obesity in combination with sarcopenia (the age-related loss of muscle mass and strength or physical function) is increasing in adults aged 65 years and older. A major subset of adults over the age of 65 is now classified as having sarcopenic obesity, a high-risk geriatric syndrome predominantly observed in an ageing population that is at risk of synergistic complications from both sarcopenia and obesity. This Review discusses pathways and mechanisms leading to muscle impairment in older adults with obesity. We explore sex-specific hormonal changes, inflammatory pathways and myocellular mechanisms leading to the development of sarcopenic obesity. We discuss the evolution, controversies and challenges in defining sarcopenic obesity and present current body composition modalities used to assess this condition. Epidemiological surveys form the basis of defining its prevalence and consequences beyond comorbidity and mortality. Current treatment strategies, and the evidence supporting them, are outlined, with a focus on calorie restriction, protein supplementation and aerobic and resistance exercises. We also describe weight loss-induced complications in patients with sarcopenic obesity that are relevant to clinical management. Finally, we review novel and potential future therapies including testosterone, selective androgen receptor modulators, myostatin inhibitors, ghrelin analogues, vitamin K and mesenchymal stem cell therapy.

Fig. 1 |. A proposed model of mechanisms leading to sarcopenic obesity.

The proposed interplay between adipose and muscle tissue, which is believed to contribute to the development of sarcopenic obesity, is shown. The black lines are stimulatory, while red lines with flat ends indicate inhibition. IGF1, insulin-like growth factor 1; TNF, tumour necrosis factor.

Fig. 2 |. MRi of individuals with and without obesity.

Cross-sectional MRI of the quadriceps area of an individual without obesity with normal muscle characteristics (part a) and an individual with obesity with small muscles and infiltration by adipose tissue (part b) is shown. More muscle tissue is visible in part a than in part b, and the higher intensity signals seen in part b indicate fat infiltration of the muscle. Images courtesy of Edward Weiss, St Louis University School of Medicine, St Louis, MO, USA.

Fig. 3 |. Mean percentage changes in physical function and lean mass during the weight loss interventions.

Measures used included a physical performance test (PPT) (scores range from 0 to 36, with higher scores indicating better functional status) (part a); the Functional Status Questionnaire (FSQ) (scores range from 0 to 36, with higher scores indicating better functional status) (part b); lean mass (part c); and strength (measured as total one repetition maximum (that is, the total of the maximum weight a participant can lift, in one attempt, in the bicep curl, bench press, seated row, knee extension, knee flexion and leg press)) (part d). Scores on the PPT were used as an objective measure of frailty (primary outcome), and scores on the FSQ were used as a subjective measure of frailty. Percentage changes are presented as least-squares-adjusted means; T bars indicate standard errors. *P < 0.05 for the comparison with the control group. **P < 0.05 for the comparison with the aerobic group. ***P < 0.05 for the comparison with the resistance group. Figure adapted with permission from REF, New England Journal of Medicine, Villareal, D. T. et al. Aerobic or resistance exercise, or both in dieting obese older adults, 376, 1943–1955 Copyright ^© (2017) Massachusetts Medical Society. Reprinted with permission.