Age-Related Changes in Insulin Resistance and Muscle Mass: Clinical Implications in Obese Older Adults

The older segment of the global population is increasing at a rapid pace. Advancements in public health and modern medicine lengthened life expectancy and reduced the burden of disease in communities worldwide. Concurrent with this demographic change is the rise in overweight people and obesity, which is evident in all age groups. There is also an aging-related reduction in muscle mass and function, or sarcopenia, that is exacerbated by sedentary lifestyle and poor nutrition. The coexistence of muscle loss and elevated body mass index, termed "sarcopenic obesity", has particularly deleterious consequences in older individuals. Worsening insulin resistance and a proinflammatory state operate at the pathophysiologic level and lead to adverse health outcomes such as a proclivity to cardiovascular disease, type 2 diabetes, and even cognitive dysfunction. Although the concept of sarcopenic obesity as a disease construct is being increasingly recognized, a clearer understanding is warranted in order to define its components and health impact. Research is needed at the molecular-cellular level to tie together derangements in insulin action, cytokines, myokines, and endothelial dysfunction with clinical outcomes. Lifestyle modifications as well as targeted nonpharmacologic approaches, such as supplements and antioxidants, appear to have a promising role in reducing the chronic burden of this emerging disorder. Breakthroughs in drug therapies that retard or even reverse the underlying dynamics of sarcopenia and obesity in older persons are being actively explored.