Effect of Sarcopenic Obesity on the Progression of Glycaemic Status in Middle-Aged and Older Adults Without Diabetes

Sarcopenia has been historically defined as the loss of skeletal muscle mass, with or without the loss of muscle strength and/or physical function. Sarcopenia is common among individuals with obesity and during the ageing process, because of multiple factors, including metabolic changes. The coexistence of excess adiposity and low muscle mass or function is referred to as sarcopenic obesity (SO), a condition increasingly recognised for its influence on important patient-centered outcomes. This study investigated the degree to which the presence of SO is related to the progression of glycaemic status in adults without diabetes, compared with those with sarcopenia only, obesity only, or neither condition.

In this population-based cohort study conducted in China, involving adults aged 45 years or older without diabetes and 18,497 person-years of follow-up, the authors observed progression rates of 26.01% from normoglycaemia to prediabetes, 8.24% from prediabetes to diabetes, and 3.34% from normoglycaemia to diabetes within the general cohort. Overall, 26.94% of participants had SO at baseline. Compared with participants without sarcopenia or obesity, those with SO exhibited a significantly higher risk of progression from normoglycaemia to diabetes after adjusting for demographic, lifestyle, and clinical factors (HR, 2.11; 95% CI, 1.10–4.04); no significant differences were observed in those with sarcopenia only or obesity only compared to the reference group. Furthermore, participants with SO (HR=1.65; 95% CI 1.04–2.63), sarcopenia only (HR, 1.78; 95% CI, 1.11–2.86), or obesity only (HR, 2.00; 95% CI, 1.29–3.12) all had a higher risk of progression from prediabetes to diabetes compared with those with neither condition.

The strengths of this study include the large population size from nationally representative data and an extensive follow-up time. In addition, the investigators used an ethnic-specific definition of sarcopenia and performed sensitivity analyses that revealed the main results were not influenced by certain definitions and exclusion criteria. However, there are some limitations to this study that are important to recognise. First, this was an observational cohort study, and lifestyle modifications made by participants during the follow-up period, which may have impacted outcomes, were not evaluated. Further, appendicular skeletal muscle mass was based on equation estimation and not direct instrument measurement (ie, DEXA), which could have led to the misclassification of sarcopenia status. In addition, data on 2-hour glucose levels from the oral glucose tolerance test were not available and may have resulted in an underestimation of prediabetes and diabetes rates. The study's findings may not be generalisable to other populations, given that it only included middle-aged and older Chinese adults and that sarcopenia was assessed according to the Asian Working Group for Sarcopenia 2019 algorithm. Further, obesity was defined based on waist circumference only in the study, which may impact the interpretation of the findings. When obesity was defined by waist circumference and BMI combined in sensitivity analysis, obesity only was associated with the progression from normoglycaemia to diabetes, and SO was not.

This study adds evidence that the prevention of SO in middle-aged and older adults may be important to protect against the progression of glycaemic status. A recently published systematic review and meta-analysis (Liu et al, 2023) showed that the pooled hazard ratio for all-cause mortality was 1.51 (95% CI 1.14–2.02; P < .001) for people with SO compared with healthy individuals, and that SO was associated with an increased risk of cardiovascular disease and related mortality, metabolic disorders, cognitive impairment, and functional limitations.¹ Future research is needed to investigate the effects of interventions that prevent sarcopenia on reducing the incidence of diabetes.