Challenges of operationalization and applicability
Unfortunately, the advantage of proposing this new abnormal body composition phenotype introduces challenges to future research endeavors. Primarily, it leads to additional debate on the diagnosis of osteosarcopenic obesity, which in turn can impact risk prediction and treatment strategies. Although the definition of osteopenia/osteoporosis has been quite widely accepted, substantial debate still exists regarding the definition of sarcopenia and even obesity [21]. Likewise, the expected prevalence of osteosarcopenic obesity in the general population is uncertain. The combination of three diagnostic criteria (for abnormal bone, muscle, and fat) may limit the number of individuals presenting with this condition, which will impact the identification of this phenotype in non-epidemiological studies in healthy populations. On the contrary, we hypothesize that the prevalence of osteosarcopenic obesity will be pronounced in those presenting with clinical conditions (e.g., cancer, diabetes, etc.).
Additional opportunities exist to identify the onset, cause, and effect of this condition. Although osteosarcopenic obesity leads to health complications (Fig. 1), it is unclear if the health implications are a cause or consequence of osteosarcopenic obesity (Fig. 2). In fact, further studies are needed to investigate the occurrence of potential reverse causality. Importantly, although future studies are needed, we anticipate that this combined phenotype will represent an advantage for risk prediction and preventive/treatment strategies in primary and secondary/tertiary care.
Fig. 2 Hypothesized interrelationships between bone, muscle, and adipose tissue in the osteosarcopenic syndrome. IMAT, intramuscular adipose tissue; GH, growth hormone; IGF, insulin-like growth factor I; ROS, reactive oxygen species. Adapted from Zamboni et al. [35], Ezzat-Zadeh et al. [44], and Roubenoff [33]