Measurements Of Total Body Potassium Research Articles

Long-term effect of childhood liver transplantation on body cell mass.

Malnutrition is common in end-stage liver disease, but a correction after transplantation is expected. Body cell mass (BCM) assessment using total body potassium (TBK) measurements is considered the gold standard for assessing nutritional status. The aim of this study was to examine the BCM and, therefore, nutritional status of long-term survivors after childhood liver transplantation. This was a longitudinal nested cohort study of patients undergoing transplantation at <18 years of age and surviving >3 years with ongoing review at our center. TBK measurements were obtained before transplantation and during long-term follow-up. BCM was calculated from TBK and was adjusted for the height raised to power p, which depended on sex (BCM/height(p)). The effects of the age at transplant, linear growth impairment, a diagnosis of biliary atresia, and steroid use were assessed. Thirty-two patients (20 males) participated; 59% had biliary atresia. The median age at transplant was 2.11 years (range = 0.38-10.92 years). Posttransplant testing was performed at a median of 7.23 years (range = 3.28-14.99 years) when they were 10.12 years old (range = 4.56-20.77 years). This cohort attained mean z scores for height, weight, and body mass index of -0.41 ± 1.36, -0.26 ± 1.14, and 0.04 ± 0.99, respectively. BCM/height(p) was reduced before transplantation but was further reduced after transplantation (P < 0.001) despite the normalization of height and weight. Weight recovery, therefore, likely came from increased fat mass and not BCM. Linear growth impairment was associated with a greater reduction in posttransplant BCM/height(p) (P = 0.02). In multivariate analyses, only an older age at transplant predicted reduced posttransplant BCM/height(p) (P = 0.02). The age at transplant, sex, steroid use, and underlying diagnosis did not predict changes in BCM/height(p) after transplantation. In conclusion, weight recovery in long-term survivors of childhood liver transplantation is likely due to increased fat mass because BCM remains reduced. Nutritional compromise persists in long-term survivors of childhood liver transplantation.

Is Weight Normalization After Childhood Liver Transplant Fat?

Introduction: Growth normalization after liver transplant is a desirable long term outcome in children with chronic liver disease. Weight recovery is usually rapid and often normalizes within a year although height recovery can be prolonged. It is unknown whether this recovery occurs as a result of increased body cell mass. Aims: To assess whether there was improvement in the body cell mass of long term survivors after liver transplant in childhood. Methods: Total body potassium (TBK) measurements to estimate metabolically active body cell mass were performed with a shadow shield whole body counter over a scanning bed. Body cell mass (BCM) was calculated from TBK measurements [BCM (kg) = (TBK*9.18)/39.1], andadjusted for height and gender (males=BCM/Ht3; females=BCM/Ht2.5). Measurements were performed before and after liver transplant. Paired t-tests were used to analyse the data.Results: Pre and post transplant measurements were available in 20 patients. There was no difference in the age of transplant or timing of TBK measurement after transplant between the genders. Body cell mass for height was significantly reduced after transplant in long term survivors (t= 3.83, p=0.00). When analysed according to gender, this was significant for boys (t=6.04, p=0.00)but not girls. Summary/Conclusions: Body cell mass was significantly reduced in long term survivors after liver transplant, especially boys. This implies that fat accumulation is the main reason for weight recovery, which may subsequently predisposethese children to obesity.

Whole body counter calibration using Monte Carlo modeling with an array of phantom sizes based on national anthropometric reference data

During construction of the whole body counter (WBC) at the Children's Nutrition Research Center (CNRC), efficiency calibration was needed to translate acquired counts of 40K to actual grams of potassium for measurement of total body potassium (TBK) in a diverse subject population. The MCNP Monte Carlo n-particle simulation program was used to describe the WBC (54 detectors plus shielding), test individual detector counting response, and create a series of virtual anthropomorphic phantoms based on national reference anthropometric data. Each phantom included an outer layer of adipose tissue and an inner core of lean tissue. Phantoms were designed for both genders representing ages 3.5 to 18.5 years with body sizes from the 5th to the 95th percentile based on body weight. In addition, a spherical surface source surrounding the WBC was modeled in order to measure the effects of subject mass on room background interference. Individual detector measurements showed good agreement with the MCNP model. The background source model came close to agreement with empirical measurements, but showed a trend deviating from unity with increasing subject size. Results from the MCNP simulation of the CNRC WBC agreed well with empirical measurements using BOMAB phantoms. Individual detector efficiency corrections were used to improve the accuracy of the model. Nonlinear multiple regression efficiency calibration equations were derived for each gender. Room background correction is critical in improving the accuracy of the WBC calibration.

A high-sensitivity multidetector whole-body counter

A prototype multidetector shadow-shield whole-body counter is presented to be used as a monitor of internal contamination and as a tool in clinical research. The counter is equipped with 16 NaI(Tl) detectors located in the central region of a shielded tunnel surrounding the subject to be measured. The accuracy of the counting efficacy predictions was tested in a group of adults with various body shapes and sizes using X-ray absorptiometry. The precision of the total body potassium measurements allows the use of the counter in clinical follow-up studies.

Comparison of different nutritional assessments and body-composition measurements in detecting malnutrition among gynecologic cancer patients

BackgroundFew studies have assessed global nutritional assessment tools and body-composition measurements in gynecologic cancer patients. ObjectiveWe aimed to assess the convergent validity of different nutritional tools such as the scored Patient-Generated Subjective Global Assessment (PG-SGA), serum albumin, skinfold-thickness measurements, and total-body potassium (TBK) and body density measurements to identify gynecologic cancer patients at risk of malnutrition. DesignWe assessed the nutritional status of 194 patients with suspected or proven gynecologic cancer according to the SGA and the scored PG-SGA, and skinfold-thickness (n = 145), TBK (n = 51), and body density measurements (n = 42) before primary treatment. ResultsAccording to the SGA and the scored PG-SGA global rating, 24% of gynecologic cancer patients were classified as malnourished. The prevalence of malnutrition was highest in ovarian (67%) and lowest in endometrial (6%) cancer patients. The ability of the PG-SGA score (P < 0.001) and albumin (P < 0.001), triceps skinfold-thickness (P = 0.041), and TBK (P = 0.005) measurements to predict the SGA was significantly better than chance. TBK significantly correlated with measurements associated with protein depletion, including age (P < 0.001), arm muscle area (P < 0.001), fat-free mass (P < 0.001), and the PG-SGA score (P = 0.009). Multiple regression analysis showed that, together, the PG-SGA score and arm muscle area adjusted for age accounted for 66% of total TBK variance. ConclusionsThe PG-SGA is significantly associated with subjective and objective parameters and is a widely recognized, clinically relevant method of evaluating nutritional status. It therefore seems most appropriate for identifying malnourishment in gynecologic cancer patients.

A new method of body habitus correction for total body potassium measurements

This paper describes an accurate and time-efficient method for the determination of total body potassium via a combination of measurements in the Birmingham whole body counter and the use of the Monte Carlo n-particle (MCNP) simulation code. In developing this method, MCNP has also been used to derive values for some components of the total measurement uncertainty which are difficult to quantify experimentally. A method is proposed for MCNP-assessed body habitus corrections based on a simple generic anthropomorphic model, scaled for individual height and weight. The use of this model increases patient comfort by reducing the need for comprehensive anthropomorphic measurements. The analysis shows that the total uncertainty in potassium weight determination by this whole body counting methodology for water-filled phantoms with a known amount of potassium is 2.7% (SD). The uncertainty in the method of body habitus correction (applicable also to phantom-based methods) is 1.5% (SD). It is concluded that this new strategy provides a sufficiently accurate model for routine clinical use.

Bioelectrical impedance analysis in the measurement of the body composition of surgical patients.

The evaluation of nutritional status in surgical patients remains a difficult problem. Bioelectrical impedance analysis (BIA) is a new method of body composition analysis which is easily performed at the bedside. This study determined the accuracy of BIA in the measurement of total body water (TBW) and potassium (TBK) in a heterogeneous group of surgical patients. The resistance and reactance components of impedance were measured with a whole body impedance analyser. Tritiated water dilution and whole body monitoring were the reference methods for TBW and TBK analysis. With the BIA technique the coefficient of variation for the estimation of TBW was 8.1 per cent and for TBK was 6.4 per cent. Allowing for the errors of the reference methods these results show that BIA is of limited value in the estimation of TBW but may provide a useful index of TBK.

Relationship between weight loss, reduction of body cell mass and inflammatory response in patients with cancer.

Reduced food intake is a major cause of continuing weight loss in patients with cancer. Previous work has suggested that an ongoing inflammatory response may also contribute to weight loss and alter the nature of body tissue loss. To examine this, body cell mass was estimated using measurements of total body potassium (TBK) in 31 patients with gastrointestinal cancer and weight loss with or without an inflammatory response (C-reactive protein level above 5 mg/l). Albumin levels, total body water and 24-h urinary creatinine clearance were also measured. When measured TBK was expressed as a percentage of predicted normal values there was a significant reduction in TBK for patients with an inflammatory response compared with that of those without (P = 0.04). However, when a different prediction equation for TBK was used this difference was not significant (P = 0.29). Therefore, it remains uncertain whether an ongoing inflammatory response in patients with cancer and weight loss contributes to loss of body cell mass.

Energy requirements during pregnancy and lactation

To estimate the energy requirements of pregnant and lactating women consistent with optimal pregnancy outcome and adequate milk production. Total energy cost of pregnancy was estimated using the factorial approach from pregnancy-induced increments in basal metabolic rate measured by respiratory calorimetry or from increments in total energy expenditure measured by the doubly labelled water method, plus energy deposition attributed to protein and fat accretion during pregnancy. Database on changes in basal metabolic rate and total energy expenditure during pregnancy, and increments in protein based on measurements of total body potassium, and fat derived from multi-compartment body composition models was compiled. Energy requirements during lactation were derived from rates of milk production, energy density of human milk, and energy mobilisation from tissues. Healthy pregnant and lactating women. The estimated total cost of pregnancy for women with a mean gestational weight gain of 12.0 kg, was 321 or 325 MJ, distributed as 375, 1200, 1950 kJ day(-1), for the first, second and third trimesters, respectively. For exclusive breastfeeding, the energy cost of lactation was 2.62 MJ day(-1) based on a mean milk production of 749 g day(-1), energy density of milk of 2.8 kJ g(-1), and energetic efficiency of 0.80. In well-nourished women, this may be subsidised by energy mobilisation from tissues on the order of 0.72 MJ day(-1), resulting in a net increment of 1.9 MJ day(-1) over non-pregnant, non-lactating energy requirements. Recommendations for energy intake of pregnant and lactating women should be updated based on recently available data.

P0231 ANTHROPOMETRY AND ACTIVE CELL MASS IN LONG-TERM SURVIVORS OF PEDIATRIC LIVER TRANSPLANTATION

Introduction: Pre-operative nutrition is known to significantly affect morbidity and outcome in pediatric liver transplant patients. Our group and others have demonstrated gains in height and weight, both pre and post transplant1. While pre-transplant gains are almost certainly a result of nutritional rehabilitation, the nature and etiology of these gains following transplantation remains unclear Methods: Patients surviving >5years after initial liver transplantation in childhood were eligible for this study. Total body potassium measurement was used to assess the metabolically active lean cell mass (MALCM). Serial Z scores for both height and weight were calculated at listing for transplant, immediately before transplant, 12months, 60months, and up to 120months post-transplant. MALCM was adjusted for height using log-log regression. Z score of zero was considered to be normal (range > −1 to <1), with scores <−1 considered suboptimal. Results: 14 eligible patients, with mean age 24months at time of transplant (range 5–80months), consented to take part in this study. Z scores at their most recent review were suboptimal for height and weight in 5/14 and 2/14 patients respectively. 3/5 patients with low height Z scores had Alagille’s syndrome. Adjusted MALCM scores, which were all within control reference values, were not significantly different before and after transplant. This suggests that nutrition and hence body composition was well managed and could be considered to be relatively independent of the underlying liver disease. Height Z scores showed persistent increment in all patients across the full period of analysis. These results imply that although pre-transplant nutrition is important, it does not appear to be a significant factor in the delayed linear growth observed in this study. Conclusion: Long-term survivors of pediatric liver transplant exhibit persistent catch up linear growth longer than other body measurements. Adjusted MALCM scores suggest that this catch up growth is affected by factors other than nutritional disorder. We speculate that these factors include post-transplantation medication, and/or specific growth factors including deficient levels of insulin growth factors, which we previously demonstrated in end stage liver disease in childhood2.

Abnormalities of Body Composition in Peritoneal Dialysis Patients

Body composition changes occur in peritoneal dialysis (PD) due to abnormalities in nutrition and hydration. We investigated abnormalities of nutrition and hydration in PD patients compared with healthy controls by measurement of total body potassium (TBK) and body water compartments. Cross-sectional comparison study. We measured TBK--an indicator of body cell mass--by whole body counting, total body water (TBW) by deuterium oxide dilution, and extracellular water (ECW) by bromide dilution in 29 PD patients and 32 controls. The absolute mean value of TBK for PD patients was not significantly lower than in controls. The ratios of observed TBK to predicted TBK from prediction formulas were compared. Equations used were those of Boddy, Bruce, Burkinshaw, and Ellis and our own equation derived from a local control database (Leeds). Observed/predicted ratios of TBK were significantly less in PD than in control subjects for all equations. Water volumes did not differ between PD and control groups. Observed/predicted ratios for TBK in PD patients correlated with serum potassium (Boddy r = 0.355, p = 0.06; Bruce r = 0.411, p < 0.05; Burkinshaw r = 0.457, p < 0.01; Leeds r = 0.412, p < or = 0.05; Ellis r = 0.356, p = 0.06) and tended to correlate with serum albumin (Bruce r = 0.343, p = 0.07; Burkinshaw r = 0.421, p < 0.05; Leeds r = 0.357, p = 0.06; Ellis r = 0.310, p = NS). There was no relationship with serum potassium in controls. Serum albumin in PD correlated with TBK (r = 0.445, p < 0.02), TBK/height (r = 0.419, p < 0.05), TBK/weight (r = 0.554, p = 0.002), and TBK/TBW (r = 0.586, p = 0.0001). Extracellular water/intracellular water (ECW/ICW) was inversely related to TBK (r = -0.455, p < 0.02 in PD; r = -0.387, p < 0.05 in controls) and to TBK/height (r = -0.446, p < 0.02 in PD; r = -0.411, p = 0.02 in controls). TBK/weight reduced with age in PD (r = -0.445, p < 0.02), as did TBK/TBW in PD (r = -0.463, p < 0.02). ECW/ICW tended to increase with age in PD (r = 0.351, p = 0.06). Observed/predicted ratio of TBK is reduced in PD patients relative to healthy controls, indicating reduced body cell mass. Serum albumin and potassium reflect TBK indices in PD. Body water volumes did not differ between PD and controls, implying no overall abnormality in hydration in the PD group. However, ECW is relatively increased compared to ICW with decreasing TBK indices, suggesting relative ECW expansion with reduction in body cell mass.

Comparison of bioelectrical impedance prediction equations for fat-free mass in a population-based sample of 75 y olds:: The NORA study

Objective We evaluated the performance of different prediction equations to estimate fat-free mass (FFM) from bioelectrical impedance analysis (BIA) in the elderly. Methods This study was based on 106 (51 male and 55 female) free-living 75-y-old subjects who participated in the Göteborg part of the Nordic Research on Ageing (NORA) study during 1991 and 1992. FFM predicted from BIA (FFM GOT) was validated against FFM estimated from measurements of total body water and total body potassium (FFM REF). FFM was calculated from BIA prediction equations for the elderly developed by Deurenberg et al. (FFM WAG) and Roubenoff et al. (FFM FHS). FFM also was calculated from an equation developed in subjects with a wide age range by Kyle et al. (FFM GEN). Bland-Altman analysis was performed to compare FFM REF with FFM GOT, FFM WAG, FFM FHS, and FFM GEN, respectively. FFM GOT also was compared with FFM derived from these published equations. Results Compared with FFM REF, the FFM FHS and FFM WAG underestimated FFM by 2.6 and 7.9 kg in males and 4.2 and 9 kg in females, respectively. The FFM GEN underestimated FFM in females by 1.3 kg but not in males (mean difference, −0.04 kg). FFM calculated from the BIA equation developed in this population (FFM GOT) neither underestimated nor overestimated FFM as compared with FFM REF, as expected. The differences between FFM GOT and FFMs predicted from these equations were of the same magnitude as that observed with FFM REF. Conclusion Different prediction equations produced different values for FFM. The age-specific equations developed in other populations underestimated FFM, whereas FFM GEN produced an unbiased estimate of FFM in males but not in females. Thus, the BIA prediction equation needs to be developed and validated in the population under study.

Assessment of nutritional status, body composition, and human immunodeficiency virus-associated morphologic changes.

Nutritional status should be assessed at regular intervals as part of management of human immunodeficiency virus (HIV) infection. The simplest approach to assessment is serial weight measurement. A comprehensive nutritional assessment includes (1) anthropometric measurements of body composition; (2) biochemical measurements of serum protein, micronutrients, and metabolic parameters; (3) clinical assessment of altered nutritional requirements and social or psychological issues that may preclude adequate intake; and (4) measurement of dietary intake. Techniques for measuring body composition of fat and lean body mass include anthropometry and bioelectric impedance analysis. Other techniques, including dual X-ray absorptiometry (DXA), hydrodensitometry, total body potassium measurement, and cross-sectional computed tomography or magnetic resonance imaging are available in research centers. Anthropometry, including waist-hip ratios, regional DXA, and cross-sectional imaging, is best for detecting morphologic changes associated with fat redistribution syndrome. Nutritional assessment and intervention in children with HIV can help to prevent stunted growth and development.

Nutritional Status and Muscle Strength in Patients with Emphysema and Severe α1-Antitrypsin Deficiency

The association between emphysema and weight loss is well known. Severe alpha(1)-antitrypsin deficiency is an important risk factor for the development of emphysema. To study nutritional status and muscle strength in patients with severe alpha(1)-antitrypsin deficiency and emphysema. Fifteen alpha(1)-antitrypsin-deficient patients with emphysema (7 men) and 18 healthy control subjects (9 men) were included in the study. Total body protein (TBP) was measured by in vivo neutron activation analysis of nitrogen. Lean body mass (LBM) was estimated from measurement of total body potassium. In analogy with body mass index (BMI), TBP index and LBM index were calculated as TBP/height squared and LBM/height squared, respectively. Respiratory muscle strength was studied by maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax), and skeletal muscle strength by handgrip test. Plasma albumin, transthyretin, and retinol-binding protein concentrations were analyzed as biochemical markers of nutritional status. In the alpha(1)-antitrypsin-deficient individuals, lung function test results were consistent with severe chronic airway obstruction, whereas the healthy control subjects had normal lung function. No significant differences were found in age, body weight, or BMI between the groups. TBP (p < 0.05), TBP index (p < 0.001), LBM index (p < 0.05), and plasma concentration of transthyretin (p < 0.01) were significantly lower in the patients than in the control subjects. There was a significant correlation between TBP and LBM (p < 0.001), and between TBP and body weight (p < 0.001). In the male subgroup, PImax (p < 0.05) and PEmax (p < 0.05) were significantly lower in the patients than in the control subjects. In the female subgroup, handgrip strength was significantly lower in the patients than in the control subjects (p < 0.05). Body weight was significantly correlated with handgrip test (p < 0.05) in the male patients. In the female patients, body weight was significantly correlated with PImax (p < 0.05), LBM with PEmax (p < 0.05), and LBM with handgrip test (p < 0.01). Reduced TBP and plasma transthyretin concentration in alpha(1)-antitrypsin-deficient patients with emphysema may indicate early signs of malnutrition.

Nutritional status in peritoneal dialysis: studies in body composition, lipoprotein metabolism and peritoneal function.

This thesis is based on clinical studies including virtually all patients treated with peritoneal dialysis in Gothenburg during the 1990s. The patients had a fundamentally altered body composition compared to healthy subjects, characterised by a reduction in body cell mass and body fat already at start of dialysis. During PD treatment. a further decrease in body cell mass was observed. Energy stores tended to normalise during the first years of treatment and remained constant thereafter, or declined subsequently. Extracellular water, calculated from the four-compartment model, was increased when patients started PD treatment and increased further, in parallel to the reduction in body cell mass. These alterations were seen in combination with a normal. or slightly reduced, body weight. Standard methods of assessing nutritional status may therefore not be valid in the dialysis population. Prediction equations to estimate total body water, used in measurements of dialysis adequacy, give erroneous results in PD patients, as shown in a study on our PD population. This may have important clinical consequences, especially in wasted patients. Reduced muscle mass is a marker of protein-energy malnutrition, and therefore simple and reliable methods to measure muscle mass are warranted. When lean body mass was calculated from creatinine generation rate and compared to lean body mass estimated from measurements of total body potassium. the agreement between the two methods was low. Furthermore, when repeated measurements of creatinine generation rate were performed, the variation coefficient was unacceptably high. Thus. creatinine generation rate cannot be recommended as a method to evaluate somatic protein status in PD patients. The lipoprotein metabolic derangements are pronounced in PD patients. in which a further increase in cholesterol and cholesterol-rich apoB-containing lipoproteins are added to the already pre-existing renal dyslipidemia. characterised by increased concentration of triglycerides and triglyceride-rich complex lipoproteins. There are indications that dialytic variables may influence this development. When peritoneal function was assessed by the Peritoneal Dialysis Capacity test at start of dialysis, it was observed that peritoneal function reflected patient characteristics and co-morbidity. Patients with systemic disease had enhanced diffusion capacity compared to patients with primary renal disorders. Furthermore, in patients with more severe co-morbidity. peritoneal protein losses were increased. Finally, elderly patients had ultrafiltration conditions that were different from those of younger patients. Peritoneal function remained essentially stable during medium-long term follow up. Body composition features in dialysis patients are similar to those seen in severe disease in general. Thus, it is difficult to separate the effects of malnutrition from the effects of the underlying disease. Specific standards for nutritional status adapted for patients with renal failure are required.

Limitations in anthropometric calculations of total body water in patients on peritoneal dialysis.

Having an accurate estimation of total body water (TBW) is essential for the evaluation of dialysis efficacy in peritoneal dialysis (PD) patients. In this study, TBW volumes were measured by tritium dilution (TBW(THO)) in 165 PD patients and compared with TBW calculations according to the Watson formulas. An alternative anthropometric formula based on the present PD population was also developed and validated in an independent sample of 29 PD patients. Furthermore, the relation between TBW(THO) and body surface area (BSA) according to the formula of Gehan was analyzed. Body composition was assessed by a four-compartment model, based on measurements of TBW(THO) and total body potassium. Mean values of TBW by the Watson formulas were almost identical to TBW(THO), and the correlation coefficient for the relationship of calculated to measured volumes was 0.89 (P = 0.001). However, both anthropometric formulas-the Watson formulas as well as the new, alternative one-overestimated TBW in obese patients and vice versa in lean patients. Similarly, TBW was underestimated in patients who were overhydrated. The correlation coefficient between TBW(THO) and BSA was 0.708 for males and 0.797 for females (P = 0.0001 for both). In obese patients, the relationship was even closer (r = 0.924 and 0.911, respectively). In conclusion, anthropometric formulas to calculate TBW showed a considerable intraindividual variability compared with measured values. This was related to body composition features, such as degree of obesity and hydration. In contrast, BSA correlated closely to TBW in obese individuals. TBW as estimated by anthropometric formulas must be analyzed with caution, especially in the very obese or very lean patient.

Energy expenditure and the body cell mass in cystic fibrosis

Poor nutritional status in patients with cystic fibrosis (CF) is associated with severe lung disease, and possible causative factors include inadequate intake, malabsorption, and increased energy requirements. Body cell mass (which can be quantified by measurement of total body potassium) provides an ideal standard for measurements of energy expenditure. The aim of this study was to compare resting energy expenditure (REE) in patients with CF with both predicted values and age-matched healthy children and to determine whether REE was related to either nutritional status or pulmonary function. REE was measured by indirect calorimetry and body cell mass by scanning with total body potassium in 30 patients with CF (12 male, mean age = 13.07 ± 0.55 y) and 18 healthy children (six male, mean age = 12.56 ± 1.25 y). Nutritional status was expressed as a percentage of predicted total body potassium. Lung function was measured in the CF group by spirometry and expressed as the percentage of predicted forced expiratory volume in 1 s. Mean REE was significantly increased in the patients with CF compared with healthy children (119.3 ± 3.1% predicted versus 103.6 ± 5% predicted, P < 0.001) and, using multiple regression techniques, REE for total body potassium was significantly increased in patients with CF ( P = 0.0001). There was no relation between REE and nutritional status or pulmonary disease status in the CF group. In conclusion, REE is increased in children and adolescents with CF but is not directly related to nutritional status or pulmonary disease.

Body composition and muscle constituents during weight loss: studies in obese patients following gastroplasty.

The influence of rapid and prolonged weight loss on body composition and muscle constituents in the obese patient is not well known. There are serious complications related to rapid and prolonged weight loss. It is of general interest to increase the understanding of the mechanisms and consequences of significant weight loss in man. In 40 obese patients, the body composition and muscle constituents were studied before and during 1 year of weight loss following gastroplasty. The study was undertaken in two groups (A and B) of obese patients, comprising 32 women and eight men, body weight 82-175 kg and aged 24-49 years. Mean BMI in group A and B was 45 (W/H(2)) and 43 (W/H(2)) respectively. Body composition was assessed by total body potassium measurements and muscle constituents were determined by analyses of muscle specimens obtained percutaneously. The preoperative body composition was found to be equal parts of lean body mass and body fat. Preoperatively, muscle constituents revealed a higher protein content per cell and a lower potassium concentration related to fat-free solids. The loss of 18-28% body fat and lean body mass occurred in equal proportions during the first 3 postoperative months of rapid weight loss, followed by a continuous decrease of body fat but not of lean body mass. The concentrations of proteins and potassium per muscle cell revealed a reduction during the period of rapid weight loss. The RNA/DNA ratio 1 year after surgery was still reduced, indicating a low protein synthesis rate. Preoperatively mean body fat accounted for 50% of the body weight in obese patients. Following weight loss, body fat, lean body mass and concentrations of proteins were reduced compared to preoperative values. After the period of rapid weight loss, with reduction of lean body mass and body fat in parallel, a progressive reduction of body fat was observed whereas the lean body mass did not decrease further. Protein synthesis rate was still low 12 months after surgery.

Value of total body potassium in assessing the nutritional status of children with end-stage liver disease.

Malnutrition is a common problem in children with end-stage liver disease (ESLD), and accurate assessment of nutritional status is essential in managing these children. In a retrospective study, we compared nutritional assessment by anthropometry with that by body composition. We analyzed all consecutive measurements of total body potassium (TBK, n = 186) of children less than 3 years old with ESLD awaiting transplantation found in our database. The TBK values obtained by whole body counting of 40K were compared with reference TBK values of healthy children. The prevalence of malnutrition, as assessed by weight (weight Z score < -2) was 28%, which was significantly lower (chi-square test, p < 0.0001) than the prevalence of malnutrition (76%) assessed by TBK (< 90% of expected TBK for age). These results demonstrated that body weight underestimated the nutritional deficit and stressed the importance of measuring body composition as part of assessing nutritional status of children with ESLD.

Loss of total body potassium during rapid weight loss does not depend on the decrease of potassium concentration in muscles. Different methods to evaluate body composition during a low energy diet.

The aim of the study was to elucidate whether combustion of skeletal muscle glycogen during a very low calorie diet (VLCD) was associated with decreased muscle potassium content. A comparison between different methods was also performed to evaluate body composition during a VLCD and a low calorie diet (LCD). Dietary treatment of obese women by VLCD and LCD. Measurements after 1 and 2 weeks of VLCD and 6 months of LCD. Fifteen perimenopausal obese women aged 46.5+/-1.3 y and 15 of 48.0+/-0.7 y of age. Skeletal muscle biopsies under local anaesthesia. Body composition measurements by means of deal-energy X-ray absorptiometry (DEXA), and measurements of total body potassium (40K) and total body nitrogen (TBN). Measurements of electrolytes and glycogen concentration in muscle samples. In the first study (1 week of VLCD) skeletal muscle glycogen decreased (P<0.01), but muscle potassium increased (P<0.01). Muscle sodium decreased (P<0.01), while muscle magnesium was unaltered. Body weight decreased by 2.9+/-0.5 kg and 40K decreased. Fat-free mass (FFM) calculated from 40K and DEXA decreased by 2.7 vs 1.9 kg (P<0.001). Body fat measured with DEXA decreased by 1.1 kg (P<0.01), but not body fat calculated from 40K. TBN decreased by 0.03+/-0.01 kg (P<0.05) and FFM calculated from TBN by 2.9+/-0.5 kg (P<0.002). In the second study, 6 months on the LCD resulted in 17.0+/-2.0 kg weight reduction and this was mainly due to reduced body fat, 14. 0+/-2.0 kg measured with DEXA and from 40K (P<0.001). The decrease in FFM was slight. One week of VLCD resulted in muscle glycogen depletion but increased muscle potassium content in spite of decreased total body potassium. FFM contributed to the main part of body weight loss during short periods of severe energy restriction, but remained unchanged during long-term dietary treatment. Body fat became mostly responsible for the body weight loss during long-term LCD. Calculations of changes of FFM from 40K and TBN seem to overestimate the FFM decrease associated with short-term VLCD. International Journal of Obesity (2000)24, 101-107