A possible low intracellular potassium in obesity

Evaluation of measurement of fat mass reduction after liposuction in obese patients

Body composition measurements are used to evaluate surgical treatment, such as bariatric surgery in overweight patients. Nowadays, there are many different methods to measure body composition available. However, none of them has been validated for use in patients after operation. The aim of the present study was to compare the amount of surgically removed fat with two different methods, bioelectrical impedance analysis (BIA) and total body potassium (TBK). Amount of removed fat during liposuction was measured 1, 2, 3, 4, 14 days, and 1 year postoperatively in 27 obese patients after liposuction. The results were compared with actual removed fat during the operation. The median fat mass removed was 4020 grams (range 1954-9655). Postoperatively there was a varying reduction in fat mass, as measured with BIA and with TBK. There was a clear difference between the range of amounts removed measured with BIA and the range of amount removed measured with TBK. This study indicates that BIA, but not TBK, is an appropriate method to measure fat mass in obese subjects in a surgical setting. BIA seems to underestimate the amount of fat removed, whereas TBK seems to overestimate it.

New equations for estimating body cell mass from bioimpedance parallel models in healthy older Germans

The objectives of this study were to assess for elderly Germans the validity of existing equations for predicting body cell mass (BCM) and to develop from single- and multifrequency bioimpedance (SFBIA, MFBIA) models new prediction equations. In a data-splitting approach, validation and cross-validation were performed in 160 healthy elderly (60- to 90-yr) subjects. BCM was determined using a tetrapolar bioimpedance analyzer (800 microA; 4 fixed frequencies: 1, 5, 50, and 100 kHz; electrodes placed to hand, wrist, ankle, and foot) and whole body (40)K counting as a reference method. New prediction equations were derived by multiple stepwise regression analysis. The Bland-Altman procedure was used for methods comparison. Relative to whole body counting, the manufacturer's equation overestimated BCM by 9% in men (P < 0.0001, paired t-test) and 4% in women (P = 0.002). Compared with the manufacturer's equation, the newly derived equations (r = 0.92, RMSE = 6-9%) improved accuracy (pure error = 13 vs. 7-8%) and reduced bias and limits of agreement. SFBIA and MFBIA equations did not differ in precision or accuracy. We conclude that the newly derived equations improved BCM estimates in the elderly compared with existing equations. There was no advantage of MFBIA over SFBIA equations.

In vivo measurement of total body chlorine using the 8.57 MeV prompt de-excitation following thermal neutron capture

Prompt gamma neutron activation analysis with 238Pu/Be sources is used to measure total body chlorine (TBCl) in vivo following the reaction 35Cl(n, gamma)36Cl. The chlorine de-excitation at 8.57 MeV is used for calibration of the system for TBCl. Body hydrogen is used as an internal standard and TBCl is derived from the gamma-ray counts ratio of chlorine to hydrogen. The precision of the method, determined from replicate scans of a Bush-type phantom, is 4.9% (CV). To assess accuracy an anthropomorphic phantom consisting of minced meat was constructed. Replicate scans of this phantom yielded a mean total chlorine which was not significantly different from the chemical analysis value. The subject dose equivalent for the activation measurement is less than 0.3 mSv. Mean TBCl values for 63 male and 107 female healthy volunteers were in broad agreement with predicted amounts based on multiple regression equations developed at other centres from measurements using the delayed gamma approach. Good agreement was observed in 76 volunteers between total body water (TBW) measured by tritium dilution, after correction for non-aqueous hydrogen exchange, and TBW derived from the sum of extracellular water and intracellular water as measured by TBCl and total body potassium (TBK), respectively.

A comparison of measurements of lean body mass derived by bioelectrical impedance, skinfold thickness and total body potassium. A study in obese and non-obese normal subjects

The measurement of body composition is an important part of metabolic and epidemiological research, but most currently available methods are complex and expensive. We have, therefore, compared measurements of fat mass (FM) and lean body mass (LBM), obtained using a commercially available bioelectrical impedance monitor (The Holtain Body Composition Monitor) (IMP), and by measuring skinfold thickness (SFT), with values obtained by measuring total body potassium (TBK). Twenty subjects, 10 with a body mass index (BMI) less than 30 (kg m-2), (non-obese) and 10 with BMI greater than or equal to 30 (obese) took part in the study. There was a strongly significant linear relationship between LBM calculated from TBK and that calculated from impedance (IMP), in both non-obese and obese groups analysed separately (non-obese: r = 0.92; p less than 0.001 and obese: r = 0.92; p less than 0.001) and together (all: r = 0.89; p less than 0.001). LBM calculated from TBK was strongly linearly correlated with values derived from SFT for non-obese (r = 0.91; p less than 0.001) but not for obese subjects. Mean values of LBM of non-obese subjects derived by each method were not significantly different (TBK: 51.3 +/- 10.40 kg; IMP: 53.18 +/- 10.37 kg; SFT: 48.87 +/- 9.48 kg), but significant differences existed when the subjects were obese (TBK: 51.86 +/- 9.65 kg; IMP: 58.69 +/- 8.55 kg; SFT: 67.61 +/- 8.14 kg; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of total adipose tissue and body fat in women by computed tomography, 40K, and tritium

The adipose tissue volumes of 12 women were determined by computed tomography (CT). Body weight ranged from 46 to 129 kg. Nine or twenty-two transsectional scans were examined with respect to the adipose tissue area. The total adipose tissue volume (ATCT22 or ATCT9) was calculated by assuming linear changes in the adipose tissue area between adjacent scans. Body fat (BF) was also calculated from total body potassium (BF40K), from total body water (BFTHO), and from both these determinations (BF40K + THO). Body mass index (BMI) was calculated by dividing body weight (BW) by height2 (H2). ATCT22, ATCT9, and BFK were more closely related to BW and BMI than were BFTHO and BF40K + THO. When ATCT was used as a standard, the optimal index of adiposity based on BW and H was in the range BW/H0.8 to BW/H1.2. From the CT and 40K measurements it was possible to deduce that the potassium content is 62 mmol/kg fat free mass and 73-75 mmol/kg lean body mass. The error of ATCT9 was 0.6%, while that of BF40K was at least three to four times larger. It is concluded that the CT-based AT determination is the most reproducible method so far available. The technique might turn out to be of great value in human energy balance experiments.