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Summary Background & aims Bioimpedance analysis-derived phase angle (PhA), as marker of body cell mass and cell integrity, might be altered in obesity, a condition which is characterized by alterations in muscle structure and function. The aim of this systematic review was to evaluate whether and to which extent PhA varies in individuals/patients with excess body weight focusing on: a) changes in PhA due to obesity; b) changes in PhA after bariatric interventions or training programs. Methods According to PRISMA criteria, a systematic literature search until February 2021 using PubMed, Embase, Scopus, and Web of Science was performed. Selection criteria included studies on patients with obesity without comorbidities other than metabolic diseases. Results A total of 278 articles were first identified. After removing duplicates and excluding studies that did not fulfil the inclusion criteria, the full text of the remaining 80 potentially relevant studies was examined to finally retrieve 11 cross-sectional and 10 longitudinal studies. Few studies have shown that PhA is lower in individuals/patients with obesity than in controls. The only study on the matter showed a decrease with age after the fourth decade of life. Four out of five studies reported consistently greater mean values in men than in women. In two studies PhA was lower in patients with severe obesity; in addition, Patients with low PhA had higher BMI and PhA was inversely correlated with fat mass. Longitudinal studies showed that PhA markedly decreased after bariatric surgery and slightly increased after training programs. Conclusions Thus, a relatively low number of studies have evaluated PhA in individuals/patients with obesity with sometimes contradictory and preliminary results. PhA might be useful to evaluate muscle quality in individuals/patients with obesity but further studies are needed to more accurately associate this variable with changes in muscle structure and strength, as well as in metabolic functions.

Background Sarcopenia gained importance in the evaluation of patients with chronic respiratory diseases, including idiopathic pulmonary fibrosis (IPF), since it may impact negatively on clinical outcomes. Aim Aim of this study is to evaluate the prevalence and factors associated with sarcopenia, defined according to the European Working Group on Sarcopenia in Older People 2 (EWGSOP2) 2019 definition, and to evaluate the prevalence of the single criteria that define the EWGSOP2 definition (muscle strength, muscle quantity and physical performance), in a cohort of consecutive patients with IPF prospectively followed up in 9 hospitals in Northern Italy between December 2018 and May 2021. Methods Enrolled patients underwent an extensive pulmonary and nutritional assessment, including bioelectrical impedance analysis, dynamometry and 4-m gait speed test, both at IPF diagnosis and at 6-month follow-up. Results Out of the 83 patients (81% males, mean age 72.5 years) with IPF at disease diagnosis enrolled in the study, 19 (22.9%) showed sarcopenia, including 2 (2.4%) with severe sarcopenia, 5 (6.0%) with confirmed sarcopenia and 12 (14.5%) with probable sarcopenia. Sarcopenia was associated with a significantly higher severity of the disease and sedentary lifestyle, while no differences were observed in regards to body mass index, history of weight loss and comorbidities between patients with and without sarcopenia. Out of the 64 patients without sarcopenia at baseline, 16 cases showed alteration of muscle quantity and/or physical performance. In the 51 patients with complete data at 6-month follow-up, there were no cases of severe sarcopenia, 1 case (2.0%) showed confirmed sarcopenia, while the prevalence of probable sarcopenia was 19.6% (10 cases). No differences in regards to antifibrotic treatment received and onset of gastrointestinal side effects were observed between patients with and without sarcopenia at follow-up. Conclusions The prevalence of sarcopenia in patients with IPF both at diagnosis and at 6-month follow-up was low but not negligible and was associated with higher severity of the disease and sedentary lifestyle. In IPF patients, a comprehensive diagnostic work-up including all the criteria defining the EWGSOP2 definition might be more useful than a series testing for prompt recognition of nutritional and physical performance abnormalities.

Objective: Obesity is characterized not only by an increase of fat mass but also by alterations in skeletal muscle. Bioimpedance analysis (BIA)-derived phase angle (PhA) may provide specific information on the inherent characteristics of fat-free mass, and is widely used as an index of poor nutritional status. The aim of this study was to describe whether and to what extent PhA varies depending on age, sex, and body mass index (BMI) in individuals with different weight status. Methods: We selected 1877 participants for this retrospective study (two weight status groups): 983 individuals with obesity (age 40 ± 13.9 y; BMI 39.5 ± 7.2 kg/m²) and 894 controls (age 40 ± 13.3 y; BMI 24.6 ± 2.7 kg/m²). Anthropometry and PhA at 50 kHz for the whole body were performed in all participants. Results: PhA was greater in men than in women, although a decline of PhA was observed with age, which was linear in women and occurred in men after 40 y of age. On the other hand, no significant differences were observed with increasing BMI in either sex; lower values might be observed when BMI >50 kg/m². Conclusions: A more detailed appraisal of BIA-derived PhA in obesity is reported in the present study, providing basic data that might be taken into consideration in prevention and clinical nutrition. Further studies are needed to explore differences of PhA in individuals with different weight status.

Objective Hand grip strength (HGS) is frequently used in clinical practice, resulting in a potential marker of nutritional status. This study aimed to develop reference values of HGS in Italian women with different categories of body mass index (BMI). Additionally, the main predictors of HGS were identified. Methods A cross-sectional study was conducted in Italian women between ages 16 and 55 y with different categories of BMI at the Department of Clinical Medicine and Surgery, Federico II University Hospital, Naples Italy. The whole sample was divided into tertiles according to BMI: 15 to 17.29 kg/m2 (T1), 17.3 to 19.9 kg/m2 (T2), and 20 to 25 kg/m2 (T3). Anthropometry, bioimpedance analysis, and muscle strength by an HGS test were evaluated. The cut-off values for HGS were developed for all participants and stratified by age group. Finally, a multivariate linear regression analysis was performed to assess the main predictors of HGS. Results A total of 529 women with a mean age of 23.2 ± 7.0 y and an average BMI of 18.9 ± 2.5 kg/m2 were analyzed. HGS was higher for the dominant hand than for the non-dominant hand in all BMI tertiles. On both sides, according to age groups, HGS increased with increasing age in T1 and T3, whereas it increased in the women between ages 20 and 30 y in T2 only. Multivariate linear regression analysis showed that predictors of HGS varied according to tertiles. Specifically, we found that body weight (R2 = 0.252) was the main predictor in T1, whereas phase angle (PhA) was the main determinant in both T2 (R2 = 0.240) and T3 (R2 = 0.216). Conclusion This study defined the normal reference values of HGS in Italian women with different BMI ranges, stratifying the sample group by age. Additionally, the main predictors of HGS were assessed for each BMI tertile. In primary malnutrition (T1), the main predictor of HGS was body weight, whereas in the other two tertiles (T2, T3), the PhA was the main predictor of HGS.

Summary Background & aims Bioelectrical impedance analysis-derived phase angle (PhA) has been gaining attention in the clinical evaluation of nutritional status because it is thought to be a proxy of water distribution and body cell mass; it is also associated to muscle strength and is an effective predictor of different clinical outcomes. Since an association may be expected between PhA and sarcopenia (defined by low skeletal muscle mass and impaired muscle function), the aim of this systematic review was to evaluate: a) changes in PhA due to sarcopenia; b) prevalence of sarcopenia according to PhA values; c) derivation of phase angle cut-offs for detecting sarcopenia; d) sarcopenia and PhA as predictors of clinical outcomes. Methods A systematic research on electronic databases (PubMed, Embase, Scopus and Web of Science) from inception to January 31st, 2020 was performed according to PRISMA checklist. Using PICOS strategy, “P” corresponded to participants of any age, gender or ethnicity, “I” designated diagnosis of sarcopenia, “C” indicated subjects without sarcopenia, “O” corresponded to PhA, and “S” selected all study types. Methodological quality was assessed using the National Institute of Health (NIH) quality assessment tool. Results Through the initial literature search and after removing duplicates and excluding papers by screening titles and abstracts, 79 potentially relevant studies were examined. Thirteen studies (7668 subjects) met the inclusion criteria. The overall risk of bias was low. Sarcopenia was associated with a significant lower PhA in seven studies out of eight, while five studies out of six reported a high prevalence of sarcopenia was in patients with low PhA. Different cut-off point values from 4.05 to 5.05° have been derived for the identification of sarcopenia. PhA and sarcopenia were independent predictors of survival in cancer patients and geriatric hospitalized patients. Conclusions Data from the selected papers demonstrate that PhA is decreased in sarcopenic subjects and the prevalence of sarcopenia is higher in subjects with low PhA. Further studies are needed to determine to what extent PhA may be valuable in detecting low muscle quality and/or identifying sarcopenia.

The assessment of body composition (BC) can be used to identify malnutrition in patients with Crohn's disease (CD). The aim of this study was to evaluate the nutritional status of CD patients by assessing BC, phase angle (PhA) and muscle strength. Differences in disease duration and medications were also considered.Consecutive adult CD patients aged 18-65 years were enrolled in this cross-sectional study. Disease activity was clinically defined by the Crohn's Disease Activity Index (CDAI) in the active and quiescent phases. All participants underwent anthropometry, BC and handgrip-strength (HGS) measurements; additionally, blood samples were taken. Data from CD patients were also compared with age-, sex- and BMI-matched healthy people.A total of 140 CD patients with a mean age of 38.8 ± 13.9 years and a mean body weight of 64.9 ± 12 kg were recruited and compared to controls. The findings showed that all nutritional parameters, especially PhA and HGS, were lower in CD patients than in controls, and these parameters were substantially impaired as disease activity increased. Active CD patients had a lower body weight and fat mass than both the quiescent and control groups. PhA was negatively correlated with age (r = -0.362; p = 0.000) and CDAI (r = -0.135; p = 0.001) but was positively associated with fat free mass (FFM) (r = 0.443; p = 0.000) and HGS (r = 0.539; p = 0.000). Similarly, serum protein markers were lower in the active CD group than in the quiescent group (p 0.05). Disease duration and medications did not significantly affect nutritional status.BIA-derived PhA is a valid indicator of nutritional status in CD patients, and its values decreased with increasing disease activity. Additionally, small alterations in BC, such as low FFM, and reduced HGS values can be considered markers of nutritional deficiency. Therefore, the assessment of BC should be recommended in clinical practice for screening and monitoring the nutritional status of CD patients.

Objective: The aim of this study was to develop and validate new predictive equations for estimating resting energy expenditure (REE) in subjects with normal weight and overweight, considering anthropometric parameters as well as raw variables from bioimpedance analysis (BIA). Methods: Adult participants with normal weight and overweight were recruited and randomly split into calibration and validation groups. Indirect calorimetry (IC) and BIA were performed in all subjects. New predictive equations were developed using the following models: model 1 with age, weight, stature, and body mass index (BMI) as predictors; and model 2: model 1 + raw BIA variables (bioimpedance index and phase angle). The accuracy of the new equations at both the group (bias) and individual (within ±10%) levels was tested in the validation group. Three published predictive equations were also compared, with the REE values measured by IC. Results: A total of 2483 adults were included for developing and validating the new equations. All selected formulas, including the new ones, showed a bias of

Background Phase angle (PhA) is a raw BIA variable that has been gaining attention in recent years because it is supposed to be an index of the ratio between extracellular and intracellular water, body cell mass, and cellular integrity. The aim of this systematic review was to evaluate the variability of PhA between different sports and its relationships with sport performance. Additionally, we investigated whether PhA depends on gender or age, and analyzed the differences between athletes and controls. Methods A systematic research using PubMed, Scopus and Web of Science up to June 2019 was performed. Selection criteria included studies on subjects who practice sports in planned and continuous modality at competitive or elite level. Results Thirty-five papers met the inclusion criteria (twenty-one cross-sectional data, fourteen longitudinal data). A few but convincing studies have shown that mean PhA is higher in athletes vs. controls. PhA increases with age and is likely to be higher in male than female athletes. A large variability in PhA is observed for the same sport, while it is still uncertain to what extent PhA differs between various sports. There are no clear relationships of PhA with sport performance or training/untraining. Conclusion It is still to be defined to what extent PhA varies between different sports and changes with training/untraining. It can be argued that for a given sport much more data should be collected in a systematic way and for a period of time appropriate in order to determine changes and trends. This is even more crucial in the case of intervention studies.

Summary Heart rate variability (HRV) is altered in obese subjects, but whether this is true also in underweight (UW) subjects is still under debate. We investigated the HRV profile in a sample of healthy adult women and its association with adiposity. Five-minute resting state electrocardiographic activity was recorded in 69 subjects grouped according to their body mass index, [23 normal weight (NW), 23 overweight/obese (OW) and 23 UW). Body fat mass (FM) was measured by bio-impedance. Frequency- and time-domain analyses were performed. Compared to NW, UW and OW subjects showed a significant decrease in HRV indices, as revealed by spectral analysis. No differences were observed between UW and OW subjects. A second-order polynomial regression unveiled an inverted U-shaped relationship between FM extent and HRV indices. A decrease of HRV indices was associated with changes in FM extent, proving that in UW and OW subjects, the adaptive flexibility of autonomic cardiac function was reduced. These findings provide important clues to guide future studies addressed to determine how changes in adiposity and autonomic cardiac function may contribute to health risk.

Background: Various criteria have been used so far for the diagnosis of malnutrition or sarcopenia in patients suffering from chronic obstructive pulmonary disease (COPD).Objective: To determine the prevalence of malnutrition and sarcopenia in COPD, as defined by international diagnostic criteria, and determine their relationships with raw BIA variables.Methods: Two-hundred and sixty-three COPD patients (185 males and 78 females) underwent both clinical examination and respiratory, anthropometric, bioelectrical impedance analysis (BIA raw variables: phase angle and impedance ratio), handgrip strength (HGS), 4 m gait speed and biochemical measurements. Malnutrition and sarcopenia were diagnosed based on European Society for Clinical Nutrition and Metabolism (ESPEN) criteria and European Working Group on Sarcopenia in Older People (EWGSOP) criteria, respectively.Results: The overall prevalence of malnutrition and sarcopenia was 19.8% and 24.0% respectively, increasing with disease severity. The prevalence of sarcopenia was significantly higher in patients with malnutrition (71.2% vs 12.3%; p < 0.001), especially in those with systemic inflammation (cachectic patients) (85.7% vs 61.3%; p < 0.001). Malnourished patients with sarcopenia had a significant reduction in BMI, fat-free mass and HGS compared to non-sarcopenic patients. Finally, impedance ratio significantly increased and phase angle decreased in patients with severe sarcopenia and in cachectic patients.Conclusion: A relatively high prevalence of malnutrition and sarcopenia was found in COPD patients applying international standard criteria, with some discrepancy between the two diagnoses. In addition, clear-cut changes in raw BIA variables were observed in malnourished patients with systemic inflammation and sarcopenic patients.

To define whether reference values for bioimpedance analysis (BIA) can be predicted in healthy individuals, individual characteristics and BIA variables resistance index=height(2)/parallel resistance and reactance index=height(2)/parallel reactance) were evaluated in non-obese healthy individuals:863 men and 769 women with an age range 20-70 years and body mass index (BMI)19.0-29.9 kg/m(2). The following predictive equations were obtained using multiple regression analysis:Resistance index (cm(2)/ohm)Males 21.06 + 0.087xage + 1.091xweight -1.801xBMI,Females 20.35 + 0.037xage + 0.878xweight - 1.343xBMIReactance index (cm(2)/ohm)Males 0.57 + 0.117xweight - 0.096xBMIFemales 1.42 + 0.078xweight - 0.075xBMI. In conclusion, reference BIA values seem to be reasonably predicted based on individual characteristics.

Childhood obesity increases the risk of morbidity whether or not obesity persists into adulthood. Measurement of body fat content using bioimpedance analysis (BIA) is a useful tool in epidemiologic studies. Both tricep skinfold thickness (TST, mm) and body mass index (BMI, kg/m(2)) are indirect, simple methods and easy to perform for assessing body composition. These methods are generally accepted as good clinical measures for defining childhood obesity. The aim of our study was to evaluate fat mass (FM, kg and %) measurements using TST and BIA (50 kHz) in a cohort of 6-year-old Italian children. A total of 228 southern Italian children (121 boys, 107 girls), randomly selected in nine local primary schools, were included in the study. The correlation between methods for measuring FM was calculated. Linear regression analysis showed a significant positive correlation between FM measured with BIA and BMI ( r=0.92, p

Anthropometry, bioimpedance analysis (BIA) and resting energy expenditure (REE) were evaluated in young female patients affected by anorexia nervosa who were either severely malnourished (MnA) or already refed (RfA) and in a control group of healthy young women (WnC). Fat-free mass (FFM) and fat mass (FM), evaluated from skinfold thickness, were severely decreased in the MnA group while they were very similar in the RfA group and in the WnC group. With respect to BIA parameters, impedance (Z) was significantly higher in absolute terms in the MnA but lower than in the other groups when expressed as specific impedance, i.e. after normalization for both FFM and height. Phase angle significantly differed between the three groups, being significantly (P < 0.01) lower in the MnA (3.70+/- 0.83 degrees) and the RfA (4.36 +/- 0.82) than in the WnC (5.17 +/- 0.40). REE was comparable in RfA subjects and WnC subjects, while it was sharply decreased (P < 0.01) in the MnA patients both in absolute value and after adjustment for body composition (FFM and FM) or body weight. This cross-sectional study shows that marked changes in BIA parameters occur in undernourished anorectic patients and also in the anorectic subjects who were previously very underweight but studied only after having already regained a normal body size. REE was deeply decreased in the undernourished anorectic women even when the differences in body composition or Wt were taken into account, indicating the occurrence of a significant adaptation of energy expenditure to chronic underfeeding.