Heymsfield, Steven B

ABSTRACT Skeletal muscle (SM) is an integral organ component in the pathophysiology of many acute and chronic diseases. But is there a ‘gold’ standard or accepted reference method for quantifying the amount and composition of human SM mass? Exploring that question led us to recognize the existence of a SM measurement paradigm that divides methods into two broad categories, in vitro and in vivo. In vitro methods quantify SM mass, weighing intact muscles as part of whole cadaver evaluations, only 51 of which are reported in medical literature with no recent additions. In vivo methods are used to evaluate SM in vivo, and two tiers were revealed in our analyses. An upper tier that included three methods considered ‘reference’ approaches for their accuracy and precision: computed tomography, magnetic resonance imaging and dual‐energy X‐ray absorptiometry. A lower in vivo method tier included bioimpedance analysis, three‐dimensional imaging, several approaches involving creatine metabolism, ultrasound and anthropometry. A feature common to all of the lower tier methods is their need for calibration or validation against reference approaches in the upper in vivo method tier. A critical review of the three in vivo reference methods in the upper tier revealed widely variable SM volume/mass acquisition protocols, image analysis methods and applied terminology. Some reports espouse an upper tier reference method as the ‘gold’ standard while providing minimal details of exactly how and what was measured, thus making replication in follow‐up studies difficult. Any technical issues related to an in vivo reference method are propagated to the in vivo methods in the lower tier that are calibrated or validated against them. Our review of in vivo reference methods of quantifying SM mass and composition led us to two broad recommendations. First, published reports including these reference methods should provide enough details related to acquisition and analysis protocols so that readers can replicate their findings. Second, an effort should be made to apply precise terminology in published reports in order to avoid confusion on exactly what was measured; suggestions are made on definitions of commonly used terms when referring to body composition compartments. Lastly, because there is no consensus on what constitutes a ‘gold’ standard for SM measurement, we suggest expert groups convene in the future to recommend optimum approaches and working guidelines for quantifying muscle mass and composition in vivo.

Abstract Cardiovascular disease (CVD) continues to be the leading cause of death in adults, highlighting the need to develop novel strategies to mitigate cardiovascular risk. The advancing obesity epidemic is now threatening the gains in CVD risk reduction brought about by contemporary pharmaceutical and surgical interventions. There are sex differences in the development and outcomes of CVD; premenopausal women have significantly lower CVD risk than men of the same age, but women lose this advantage as they transition to menopause, an observation suggesting potential role of sex hormones in determining CVD risk. Clear differences in obesity and regional fat distribution among men and women also exist. While men have relatively high fat in the abdominal area, women tend to distribute a larger proportion of their fat in the lower body. Considering that regional body fat distribution is an important CVD risk factor, differences in how men and women store their body fat may partly contribute to sex‐based alterations in CVD risk as well. This article presents findings related to the role of obesity and sex hormones in determining CVD risk. Evidence for the role of sex hormones in determining body composition in men and women is also presented. Lastly, the clinical potential for using sex hormones to alter body composition and reduce CVD risk is outlined. © 2022 American Physiological Society. Compr Physiol 12:1‐45, 2022.

Abstract Background The Global Leadership Initiative on Malnutrition (GLIM) approach to malnutrition diagnosis is based on assessment of three phenotypic (weight loss, low body mass index, and reduced skeletal muscle mass) and two etiologic (reduced food intake/assimilation and disease burden/inflammation) criteria, with diagnosis confirmed by fulfillment of any combination of at least one phenotypic and at least one etiologic criterion. The original GLIM description provided limited guidance regarding assessment of inflammation, and this has been a factor impeding further implementation of the GLIM criteria. We now seek to provide practical guidance for assessment of inflammation. Methods A GLIM‐constituted working group with 36 participants developed consensus‐based guidance through a modified Delphi review. A multiround review and revision process served to develop seven guidance statements. Results The final round of review was highly favorable, with 99% overall “agree” or “strongly agree” responses. The presence of acute or chronic disease, infection, or injury that is usually associated with inflammatory activity may be used to fulfill the GLIM disease burden/inflammation criterion, without the need for laboratory confirmation. However, we recommend that recognition of underlying medical conditions commonly associated with inflammation be supported by C‐reactive protein (CRP) measurements when the contribution of inflammatory components is uncertain. Interpretation of CRP requires that consideration be given to the method, reference values, and units (milligrams per deciliter or milligram per liter) for the clinical laboratory that is being used. Conclusion Confirmation of inflammation should be guided by clinical judgment based on underlying diagnosis or condition, clinical signs, or CRP.