M. Marra

Early Changes in Bioelectrical Estimates of Body Composition in Chronic Kidney Disease

The aim of this study was to detect the potential occurrence of early abnormalities of body composition in patients with chronic kidney disease (CKD) at first referral to an outpatient nephrology clinic. Eighty-four patients with CKD (49 men and 35 women) were compared with 604 healthy control subjects (298 men and 306 women). Anthropometry and bioelectrical impedance analysis (BIA) were performed in all participants, whereas renal function, laboratory tests for nutritional status, and nutrient intake were assessed in the CKD group only. Creatinine clearance was 27.8 +/- 13.8 and 27.4 +/- 13.0 ml/min per 1.73 m(2) in male and female patients with CKD, respectively. No patient showed peripheral edema; frank malnutrition, defined by presence of serum albumin <3.5 g/dl plus body mass index <20 kg/m(2); or protein intake <0.6 g/kg per d. At the BIA, patients with CKD showed lower resistance (R) and abnormal mean impedance vectors for the bivariate normal distribution of R/height and reactance/height. Phase angle also was reduced (-22%), especially in patients with diabetes. When BIA-derived data were considered, total body water was slightly higher (+4.3% in men; +3.5% in women) and body cell mass was lower (-6.7% in men; -7.7% in women) in patients with CKD. No difference in either BIA parameters or nutritional indexes was observed among various CKD stages. Despite the absence of overt malnutrition, patients with CKD exhibit altered BIA variables from the early phases of renal disease. These alterations are related to the renal dysfunction, are more marked in the presence of diabetes, and mainly indicate the presence of overhydration in the absence of edema. Therefore, BIA represents an attractive clinical tool to detect impairment of body composition from the early stages of CKD.

Fasting Respiratory Quotient as a Predictor of Long-Term Weight Changes in Non-Obese Women

Background/Aims: The identification of metabolic and environmental predictors of excess body fat is still far from being achieved. The aim of this study was to evaluate whether respiratory quotient in non-obese women is a predictor of body weight changes after a 6-year follow-up period. Methods: Forty-three non-obese healthy women participated in the study. Their baseline general characteristics were: age 40.5 ± 12.8 years; height 159 ± 7 cm; weight 61.8 ± 10.1 kg, and body mass index (BMI) 24.4 ± 3.8 kg/m². At baseline basal metabolic rate and respiratory quotient were determined by indirect calorimetry, while weight and BMI were recorded at the first observation and after the 3- and 6-year follow-ups. Results: At the first observation basal metabolic rate was 5,360 ± 713 kJ/day and respiratory quotient 0.850 ± 0.052. After 6 years, with weight changes equal to 1.4 ± 4.5 kg, baseline respiratory quotient was a significant predictor (p < 0.05) of changes in body weight or BMI together with baseline BMI. Conclusions: This follow-up study confirms that a high respiratory quotient (measured on free diet) predisposes to weight gain, especially in women with the highest baseline respiratory quotient (above the 90th percentile of the distribution for this variable).

Changes in bioimpedance analysis after stable refeeding of undernourished anorexic patients

OBJECTIVE: To evaluate bioimpedance analysis (BIA) parameters in patients with anorexia nervosa when undernourished and then after stable refeeding.DESIGN: Follow-up study.SUBJECTS: Thirteen patients with anorexia nervosa who were studied when undernourished (body weight (Wt): 36.9±5.6 kg, body mass index (BMI): 14.8±1.8 kg/m2) and after stable refeeding (Wt: 52.9±7.1 kg, BMI: 21.2±2.3 kg/m2) compared to 25 well-nourished control women (Wt: 53.7±4.9 kg, BMI: 21.1±1.3 kg/m2).MEASUREMENTS: Impedance and phase angle were determined for the whole body (13 patients) and separately for arms and legs (10 patients).RESULTS: Bioimpedance index (height2/impedance) and phase angle were lower in the undernourished group. Whole-body impedance declined (median, min-max) by 45, 1-151 Ohm after refeeding; the variations of bioimpedance index (BI-Index) were weakly correlated (P<0.10) with BMI changes. Limb phase angles increased with refeeding, but only changes in whole-body phase angle were correlated (P<0.025) with the corresponding variations of Wt or BMI.CONCLUSION: Whole-body phase angle increased after weight recovery of anorexic patients, suggesting the occurence of modifications in the extracellular-to-intracellular water ratio. These changes were proportional to the increase in BMI and Wt.

Prognostic significance of bioelectrical impedance phase angle in advanced cancer: preliminary observations.

Bioelectrical impedance-derived phase angle is a potentially sensible indicator of protein-energy malnutrition and of fat-free mass loss, frequent in patients with advanced cancer. We evaluated in 13 patients with advanced cancer some biochemical (serum albumin, lymphocyte count, cholesterol, cholinesterase) and clinical (Karnofsky index, Subjective Global Assessment, dietary inquiry) parameters and bioelectrical impedance analysis was performed. In addition to albumin, cholinesterase, and the Karnofsky index, phase angle (R(2)=0.384, P=0.024) was found to be strictly related to survival time and can be therefore considered a prognostic tool in patients with advanced cancer.

Comparison of bioelectrical impedance analysis and dual-energy X-ray absorptiometry for the assessment of appendicular body composition in anorexic women

Objective: To establish the accuracy of bioelectrical impedance analysis (BIA) for the assessment of appendicular body composition in anorexic women.Design: Cross-sectional study.Setting: Outpatient University Clinic.Subjects: A total of 39 anorexic and 25 control women with a mean (s.d.) age of 21 (3) y.Methods: Total, arm and leg fat-free mass (FFM) were measured by dual-energy X-ray absorptiometry and predicted from total and segmental BIA at 50 kHz. The predictor variable was the resistance index (Rl), that is, the ratio of height 2 to body resistance for the whole body and the ratio of length2/limb resistance for the arm and leg.Results: Predictive equations developed on controls overestimated total, arm and leg FFM in anorexics (P<0.0001). Population-specific equations gave a satisfactory estimate of total and appendicular FFM in anorexics (P=NS) but had higher percent root mean square errors (RMSEs%) as compared to those developed on controls (8% vs 5% for whole body, 12% vs 10% for arm and 10% vs 8% for leg). The accuracy of the estimate of total and leg FFM in anorexics was improved by adding body weight (Wt) as a predictor with Rl (RMSE%=5% vs 8% and 7% vs 10%, respectively). However, the same accuracy was obtained using Wt alone, suggesting that in anorexics, BIA at 50 kHz is not superior to Wt for assessing total and leg FFM.Conclusions: BIA shows some potential for the assessment of appendicular body composition in anorexic women. However, Wt is preferable to BIA at 50 kHz on practical grounds. Further studies should consider whether frequencies >50 kHz give better estimates of appendicular composition in anorexics as compared to Wt.Sponsorship: University of Napoli.

Bioelectrical impedance phase angle in constitutionally lean females, ballet dancers and patients with anorexia nervosa

Background/objective:Several articles have described body composition in anorexia nervosa, whereas little is known about this issue in underweight ballet dancers and constitutionally lean females. The main aim of this study was to assess whether phase angle (a bioimpedance variable related to body cell mass) differs according to the type of underweight in female adolescents and young women.Subjects/methods:Skinfold thicknesses and bioimpedance analysis (whole body and limbs) were evaluated in three groups of underweight patients (30 patients with anorexia nervosa, 10 constitutionally lean individuals and 15 classical dancers) and 30 normal weight controls.Results:There were no differences between the three groups of underweight patients with respect to anthropometric and bioelectrical impedance analysis (BIA) variables with the exception of phase angle. The latter was significantly higher in dancers, lower in anorectic patients and not different in constitutionally lean patients, as compared with controls.Conclusions:Phase angle (assessed by single-frequency BIA) appears to discriminate between different forms of underweight, being an effective marker of qualitative changes in body composition.

The prediction of basal metabolic rate in female patients with anorexia nervosa

OBJECTIVE: To evaluate in female patients with anorexia nervosa the accuracy of a specific predictive formula for basal metabolic rate (BMR) already proposed in the literature and to derive a new disease-specific equation with the same purpose.DESIGN: Cross-sectional study.SUBJECTS: One-hundred and twenty adolescent girls (<18 y) and young-adult women (18–30 y) with anorexia nervosa.MEASUREMENTS: BMR was determined by indirect calorimetry or predicted according to the Schebendach formula, which was specifically derived for anorexia nervosa.RESULTS: On average the Schebendach formula performed well in the adolescent group but not in the young-adult group. The range including 95% of the predicted–measured differences was in both cases wider than 2000 kJ/day. In the young-adult patients the accuracy of the prediction was also related to age and body mass index. Weight and age (but not height or body mass index) emerged as predictors of BMR in the sample as a whole, and only weight when the two age groups were considered separately, thus leading to three different equations. The intercepts of these regression lines were very close and not significantly different from zero while their standard error of estimate was 500–550 kJ/day.CONCLUSION: The Schebendach formula is not very accurate in estimating the BMR of female anorectic patients. Moreover, in this group the relationship between BMR and weight was altered. The predictive formulas proposed by the present study have a reasonable prediction power.

Are the general equations to predict BMR applicable to patients with anorexia nervosa

Aim: To determine whether the general equations to predict basal metabolic rate (BMR) can be reliably applied to female anorectics. Individuals and Methods: Two hundred and thirty-seven female patients with anorexia nervosa (AN) were divided into an adolescent group [n=43, 13–17 yrs, 39.3±5.0 kg, body mass index (BMI) (weight/height2) 15.5±1.8 kg/m2] and a young-adult group (n=194, 18–40 yrs, 40.5±6.1 kg, BMI 15.6±1.9 kg/m2). BMR values determined by indirect calorimetry were compared with those predicted according to either the WHO/FAO/UNU or the Harris-Benedict general equations, or using the Schebendach correction formula (proposed for adjusting the Harris-Benedict estimates in anorectics). Results: Measured BMR was 3658±665 kJ/day in the adolescent and 3907±760 kJ/day in the young-adult patients. In the adolescent group, the differences between predicted and measured values were (mean±SD) 1466±529 kJ/day (+44±21%) for WHO/FAO/UNU, 1587±552 kJ/day (+47±23%) for the Harris-Benedict and −20±510 kJ/day for the Schebendach (+1±13%), while in the young-adult group the corresponding values were 696±570 kJ/day (+24±24%), 1252±644 kJ/day (+37±27%) and −430±640 kJ/day (−9±16%). The bias was negatively associated with weight and BMI in both groups when using the WHO/FAO/UNU and Harris-Benedict equations, and with age in the young-adult group for the Harris-Benedict and Schebendach equations. Conclusions: The WHO/FAO/UNU and Harris-Benedict equations greatly overestimate BMR in AN. Accurate estimation is to some extent dependent on individual characteristics such as age, weight or BMI. The Schebendach correction formula accurately predicts BMR in female adolescents, but not in young adult women with AN.

The prediction of total body water from bioelectrical impedance in patients with anorexia nervosa

Total body water (TBW) was measured by deuterium oxide (D2O) dilution and predicted from bioelectrical impedance (Z) in nineteen anorexic and twenty-seven control women. The equation of Kushner et al. (1992) based on the impedance index (ZI = height2/Z) gave biases of 0.9 (SD 2.5) and 0.8 (SD 2.5) litres in controls and patients respectively (NS, ANOVA). The ZI-based equation of Deurenberg et al. (1993) gave biases of 1.5 (SD 2.4) litres (NS) and 3.0 (SD 2.1) litres (P < 0.001) in controls and patients respectively. Despite the fact that weight was the most powerful predictor of TBW on the study sample (n 46, r2 0.90, P < 0.0001, SE of the estimate 1.6 litres, CV 5.7%), the formulas of Segal et al. (1991) and Kushner et al. (1992) based on the association of weight and ZI gave an inaccurate prediction of TBW in both control and anorexic subjects, with a bias ranging from -3.2 (SD 2.4) to 2.9 (SD 2.1) litres (P < or = 0.001). Population-specific formulas based on ZI (n 46) gave a more accurate prediction of TBW by bioelectrical impedance analysis on the study subjects, with biases of -0.1 (SD 1.8) and 0.5 (SD 1.7) litres in controls and patients respectively (NS). However, the individual bias was sometimes high. It is concluded that bioelectrical impedance analysis can be used to predict TBW in anorexic women at a population level, but the predictions are less good than those based on body weight alone.

Evidence of brown fat activity in constitutional leanness.

BACKGROUND Brown adipose tissue (BAT) was considered essentially nonexistent in adults until recent evidence obtained using 18-fluorodeoxyglucose (18-FDG) positron emission tomography/computed tomography. It seems to play a role in whole body metabolism, but it has not been evaluated in underweight conditions, such as in young females with constitutional leanness (CL) or anorexia nervosa (AN). SUBJECTS AND METHODS Thirty-eight subjects were evaluated from October 2011 to March 2012 : 7 CL (21.7 ± 3.6 y, body mass index [BMI] 16.2 ± 1.0 kg/m(2)), 7 AN (23.4 ± 4.5 y, BMI 15.5 ± 0.8), 3 of the 7 AN after stable refeeding (R-AN, 21.3 ± 1.5 y, BMI 18.8 ± 1.1), and 24 normal weight (NW) women (25.6 ± 3.9 y, BMI 22.2 ± 1.5). Fasting resting metabolic rate and respiratory quotient were measured by indirect calorimetry, body composition by bioimpedentiometry (only in CL, AN, and refed AN), and BAT activity by 18-FDG positron emission tomography/computed tomography scan, all in standardized conditions. RESULTS All CL (100%), none of the AN and refed AN (0%), and 3 of the 24 NW (12%) subjects showed FDG uptake. Average FDG maximum standardized uptake value was 11.4 + 6.7 g/mL in CL and 5.5 ± 1.2 g/mL (min 3.7, max 8.3) in the 3 NW subjects. In CL, the maximum standardized uptake value was directly correlated to resting metabolic rate, corrected for fat-free mass, and inversely correlated with respiratory quotient. CONCLUSION BAT activity has been shown in CL in resting thermoneutral conditions and may exert a role against adipose tissue deposition.