Body Composition: Key Words
Undernutrition is insufficiently detected in in- and outpatients, and this is likely to worsen during the next decades. The increased prevalence of obesity together with chronic illnesses associated with fat-free mass (FFM) loss will result in an increased prevalence of sarcopenic obesity. In patients with sarcopenic obesity, weight loss and the body mass index lack accuracy to detect FFM loss. FFM loss is related to increasing mortality, worse clinical outcomes, and impaired quality of life. In sarcopenic obesity and chronic diseases, body composition measurement with dual-energy X-ray absorptiometry, bioelectrical impedance analysis, or computerized tomography quantifies the loss of FFM. It allows tailored nutritional support and disease-specific therapy and reduces the risk of drug toxicity. Body composition evaluation should be integrated into routine clinical practice for the initial assessment and sequential follow-up of nutritional status. It could allow objective, systematic, and early screening of undernutrition and promote the rational and early initiation of optimal nutritional support, thereby contributing to reducing malnutrition-induced morbidity, mortality, worsening of the quality of life, and global health care costs.
Sarcopenic obesity is associated with decreased survival and increased therapy toxicity in cancer patients [5–10], whereas FFM loss is related to decreased survival, a negative clinical outcome, increased health care costs , and impaired overall health, functional capacities, and quality of life [4–11]. Therefore, the detection and treatment of FFM loss is a major issue of public health and health costs .
Weight loss and the body mass index (BMI) lack sensitivity to detect FFM loss . In this review, we support the systematic assessment of FFM with a method of body composition evaluation in order to improve the detection, management, and follow-up of undernutrition. Such an approach should in turn reduce the clinical and functional consequences of diseases in the setting of a cost- effective medico-economic approach (fig. 1). We discuss the main applications of body composition evaluation in clinical practice (fig. 2).
Fig. 1. Conceptualization of the expected impact of early use of body composition for the screening of fat-free loss and under-nutrition in sarcopenic overweight and obese subjects. An increased prevalence of overweight and obesity is observed in all Western and emerging countries. Simultaneously, the aging of the population, the reduction of the level of physical activity, and the higher prevalence of chronic dis- eases and cancer increased the number of patients with or at risk of FFM impairment, i.e. sarcopenia. Thus, more patients are presenting with ‘sarcopenic over- weight or obesity’. In these patients, evaluation of nutritional status using anthropometric methods, i.e. weight loss and calculation of BMI, is not sensitive enough to detect FFM impairment. As a result, undernutrition is not detected, worsens, and negatively impacts morbidity, mortality, LOS, length of recovery, quality of life, and health care costs. On the contrary, in patients with ‘sarcopenic overweight or obesity’, early screening of undernutrition with a dedicated method of body composition evaluation would allow early initiation of nutritional support and, in turn, improvements of nutritional status and clinical outcome.
Rationale for a New Strategy for the Screening of Undernutrition
Screening of Undernutrition Is Insufficient
Body composition evaluation is a valuable technique to assess nutritional status. Firstly, it gives an evaluation of nutritional status through the assessment of FFM. Secondly, by measuring FFM and phase angle with BIA, it allows evaluation of the disease prognosis and outcome.
BIA measures the phase angle . A low phase angle is related to survival in oncology [46–50], HIV infection/ AIDS , amyotrophic lateral sclerosis , geriatrics , peritoneal dialysis , and cirrhosis . The phase angle threshold associated with reduced survival is variable: less than 2.5 degrees in amyotrophic lateral sclerosis patients , 3.5 degrees in geriatric patients , from less than 1.65 to 5.6 degrees in oncology patients [47–50], and 5.4 degrees in cirrhotic patients . The phase angle is also associated with the severity of lymphopenia in AIDS , and with the risk of postoperative complications among gastrointestinal surgical patients . The relation of phase angle with prognosis and disease severity reinforces the interest in using BIA for the clinical management of patients with chronic diseases at high risk of undernutrition and FFM loss.
In summary, FFM loss or a low phase angle is related to mortality in patients with chronic diseases, cancer (in- cluding obesity cancer patients), and elderly patients in long-stay facilities. A low FFM and an increased FM are associated with an increased LOS in adult hospitalized patients. The relation between FFM loss and clinical out- come is clearly shown in patients with sarcopenic obesity. In these patients, as the sensitivity of BMI for detecting FFM loss is strongly reduced, body composition evalua- tion appears to be the method of choice to detect under- nutrition in routine practice. Overall, the association between body composition, phase angle, and clinical outcome reinforces the pertinence of using a body com- position evaluation in clinical practice.
Compared with other techniques of body composition evaluation, the lack of reproducibility and sensitivity of the 4-skinfold method limits its use for the accurate measurement of body composition in clinical practice [33, 34]. However, in patients with cirrhosis [39, 40], COPD , and HIV infection , measurement of the mid- arm muscle circumference could be used to assess sarcopenia and disease-related prognosis. DEXA allows non- invasive direct measurement of the three major components of body composition. The measurement of bone mineral tissue by DEXA is used in clinical practice for the diagnosis and follow-up of osteoporosis. As the clinical conditions complicated by osteoporosis are often associated with undernutrition, i.e. elderly women, patients with organ insufficiencies, COPD , inflammatory bowel diseases, and celiac disease, DEXA could be of the utmost interest for the follow-up of both osteoporosis and nutritional status. However, the combined evaluation of bone mineral density and nutritional status is difficult to implement in clinical practice because the reduced accessibility of DEXA makes it impossible to be performed in all nutritionally at-risk or malnourished patients. The principles and clinical utilization of BIA have been largely described in two ESPEN position papers [45, 66]. BIA is based on the capacity of hydrated tissues to conduct electrical energy. The measurement of total body impedance allows estimation of total body water by assuming that total body water is constant. From total body water, validated equations allow the calculation of FFM and FM , which are interpreted according to reference values . BIA is the only technique which allows calculation of the phase angle, which is correlated with the prognosis of various diseases. BIA equations are valid for: COPD ; AIDS wasting ; heart, lung, and liver transplantation ; anorexia nervosa  patients, and elderly subjects . However, no BIA-specific equations have been validated in patients with extreme BMI (less than 17 and higher than 33.8) and dehydration or fluid overload [45, 66]. Nevertheless, because of its simplicity, low cost, quickness of use at bedside, and high interoperator reproducibility, BIA appears to be the technique of choice for the systematic and repeated evaluation of FFM in clinical practice, particularly at hospital admission and in chronic diseases. Finally, through written and objective re- ports, the wider use of BIA should allow improvement of the traceability of nutritional evaluation and an increase in the recognition of nutritional care by the health authorities. Recently, several data have suggested that CT images targeted on the 3rd lumbar vertebra (L3) could strongly predict whole-body fat and FFM in cancer patients, as compared with DEXA [7, 67]. Interestingly, the evaluation of body composition by CT presents great practical significance due to its routine use in patient diagnosis, staging, and follow-up. L3-targeted CT images evaluate FFM by measuring the muscle cross-sectional area from L3 to the iliac crest by use of Hounsfield unit (HU) thresholds (–29 to +150) [5, 7]. The muscles included in the calculation of the muscle cross-sectional area are psoas, paraspinal muscles (erector spinae, quadratus lumborum), and abdominal wall muscles (transversus abdominis, external and internal obliques, rectus ab- dominis) . CT also provided detail on specific muscles, adipose tissues, and organs not provided by DEXA or BIA. L3-targeted CT images could be theoretically per- formed solely, since they result in X-ray exposition similar to that of a chest radiography.
In summary, DEXA, BIA, and L3-targeted CT images could all measure body composition accurately. The technique selection will depend on the clinical context, hard- ware, and knowledge availability. Body composition evaluation by DEXA should be performed in patients having a routine assessment of bone mineral density. Also, analysis of L3-targeted CT is the method of choice for body composition evaluation in cancer patients. Body composition evaluation should also be done for every abdominal CT performed in patients who are nutritionally at risk or undernourished. Because of its simplicity of use, BIA could be widely implemented as a method of body com- position evaluation and follow-up in a great number of hospitalized and ambulatory patients. Future research will aim to determine whether a routine evaluation of body composition would allow early detection of the in- creased FFM catabolism related to critical illness .
In summary, the measurement of FFM should help ad- just the calculation of energy needs (expressed as kcal/kg FFM) and optimize nutritional support in critical cases other than anorexia nervosa.
In summary, body composition evaluation is of the utmost interest for the follow-up of nutritional support and its impact on body compartments.
In summary, measurement of FFM should be implemented in cancer patients treated with chemotherapy. Clinical studies are needed to demonstrate the importance of measuring body composition in patients treated with other medical treatments.
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