Human body composition: in vivo methods

High prevalence of metabolic syndrome in Mexico

BACKGROUND

Our objective was to describe the prevalence of the metabolic syndrome using World Health Organization (WHO) and National Cholesterol Education Program (NCEP-III) definitions in a population-based survey.

METHODS

We performed an analysis of data from a Mexican nationwide, population-based study. The population was composed of 2,158 men and women aged 20-69 years sampled after a 9-12 h fasting period. Prevalence of the metabolic syndrome as defined by the NCEP-III definition and WHO criteria was estimated and case characteristics were assessed.

RESULTS

Age-adjusted prevalence was 13.61% for WHO criteria and 26.6% for the NCEP-III definition. Prevalence was 9.2 and 21.4%, respectively, in subjects without diabetes. Thirty five percent of affected cases were <40 years of age. In addition to criteria used for diagnosis, ca. 90% were either overweight or obese. In cases detected using WHO criteria, antihypertensive treatment or blood pressure reading >140/90 was found in 61.8%. The proportion of subjects who qualified for hypolipemiant treatment was lower: lifestyle modifications were needed in 42.1% and drug therapy was required in 18.9%. The same trends were found for cases detected using the NCEP definition.

CONCLUSIONS

Prevalence of the metabolic syndrome in Mexico is high. A large proportion of affected cases qualify for preventive actions for complications of the metabolic syndrome (i.e., weight loss, antihypertensive or hypolipemiant treatment). These results provide data for planning therapeutic programs for Mexican patients with the metabolic syndrome.

Nutritional support in 111 pediatric intensive care units: a European survey

OBJECTIVE

To study current strategies in nutritional management of pediatric intensive care units (PICUs) in Europe, focusing on energy requirements.

DESIGN AND SETTING

Survey by a 35-item questionnaire sent to representatives of 242 PICUs in 28 countries. Addresses were obtained from national PICU associations and the members' list of the European Society of Pediatric and Neonatal Intensive Care.

PARTICIPANTS

Staff members of 111 European PICUs (46%) from 24 countries.

MEASUREMENTS AND RESULTS

Predominantly physicians were reported to be responsible for nutritional support. In 73% of PICUs a multidisciplinary nutritional team was available. In most PICUs daily energy requirements were estimated using weight, age, predictive equations and correction factors. In 17% of PICUs energy expenditure was regularly measured by indirect calorimetry. Nutritional status was mostly assessed by weight, physical examination, and a wide range of biochemical blood parameters. Approximately 70% of PICUs used dedicated software for nutritional support. A similar percentage of PICUs regarded "nutrition" as a research topic and part of the residents' training program.

CONCLUSIONS

Most European PICUs regard nutritional support as an important aspect of patient care, as shown by the presence of nutritional teams, software, research, and education. However, energy requirements of pediatric intensive care patient were based predominantly on estimations rather than on measurements.

Evaluation of a quantitative magnetic resonance method for mouse whole body composition analysis

OBJECTIVE

To evaluate applicability, precision, and accuracy of a new quantitative magnetic resonance (QMR) analysis for whole body composition of conscious live mice.

RESEARCH METHODS AND PROCEDURES

Repeated measures of body composition were made by QMR, DXA, and classic chemical analysis of carcass using live and dead mice with different body compositions. Caloric lean and dense diets were used to produce changes in body composition. In addition, different strains of mice representing widely diverse populations were analyzed.

RESULTS

Precision was found to be better for QMR than for DXA. The coefficient of variation for fat ranged from 0.34% to 0.71% compared with 3.06% to 12.60% for DXA. Changes in body composition in response to dietary manipulation were easily detected using QMR. An increase in fat mass of 0.6 gram after 1 week (p < 0.01) was demonstrated in the absence of hyperphagia or a change in mean body weight.

DISCUSSION

QMR and DXA detected similar fat content, but the improved precision afforded by QMR compared with DXA and chemical analysis allowed detection of a significant difference in body fat after 7 days of consuming a diet rich in fat even though average body weight did not significantly change. QMR provides a very precise, accurate, fast, and easy-to-use method for determining fat and lean tissue of mice without the need for anesthesia. Its ability to detect differences with great precision should be of value when characterizing phenotype and studying regulation of body composition brought about by pharmacological and dietary interventions in energy homeostasis.

Total body water measurements using resonant cavity perturbation techniques

A recent paper proposed a novel technique for determining the total body water (TBW) of patients suffering with abnormal hydration levels, using a resonant cavity perturbation method. Current techniques to measure TBW are limited by resolution and technical constraints. However, this new method involves measuring the dielectric properties of the body, by placing a subject in a large cavity resonator and measuring the subsequent change in its resonant frequency, fres and its Q-factor. Utilizing the relationship that water content correlates to these dielectric properties, it has been shown that the measured response of these parameters enables determination of TBW. Results are presented for a preliminary study using data estimated from anthropometric measurements, where volunteers were asked to lie and stand in an electromagnetic screened room, before and after drinking between 1 and 2 l of water, and in some cases, after voiding the bladder. Notable changes in the parameters were observed; fres showed a negative shift and Q was reduced. Preliminary calibration curves using estimated values of water content have been developed from these results, showing that for each subject the measured resonant frequency is a linear function of TBW. Because the gradients of these calibration curves correlate to the mass-to-height-ratio of the volunteers, it has proved that a system in which TBW can be unequivocally obtained is possible. Measured values of TBW have been determined using this new pilot-technique, and the values obtained correlate well with theoretical values of body water (r = 0.87) and resolution is very good (750 ml). The results obtained are measurable, repeatable and statistically significant. This leads to confidence in the integrity of the proposed technique.

Regulation of body composition by androgens

Human body can be viewed simplistically as being composed of fat-free and fat mass. With more sophisticated techniques, body composition can be broken down into fat mass, skeletal muscle mass, nonmuscle lean mass, visceral mass and bone mineral content. Similarly, it is possible to obtain estimates of total body water and intracellular and extracellular water contents. Regardless of the model of body composition assessment, it is evident that androgens are important determinants of body composition; there is no body compartment that is not directly or indirectly affected by androgens. The effects of androgens on skeletal muscle mass have received the greatest attention in recent literature; however, growing body of evidence suggests that androgens also regulate fat mass, bone mineral content, nonmuscle soft tissues and body water.

Validity of six field and laboratory methods for measurement of body composition in boys

OBJECTIVE

To determine the validity of the following six body composition methods against a reference method (three-component model): air displacement plethysmography (BODPOD); estimation from body density using BODPOD; skinfold thickness using the Slaughter equations; bioelectrical impedance, both leg-leg (TANITA) and hand-foot (Bodystat) approaches; and total body water.

RESEARCH METHODS AND PROCEDURES

Forty-two healthy white 10- to 14-year-old boys (mean age, 12.9 +/- 1.0 years) were enrolled in this study. Measures of body fat percentage and body fat mass derived from the three-component model were used as the reference method. Validity of all of the other methods was assessed by comparison against the reference by calculation of biases and limits of agreement.

RESULTS

Mean body fatness measured using the reference method was 16.4 +/- 11.6% and 8.7 +/- 7.0 kg. Estimates of fatness from total body water had the narrowest limits of agreement relative to the reference (+0.9 +/- 5.0% body fat; +0.5 +/- 2.9 kg fat mass). For all other methods tested, we observed large biases and very wide limits of agreement.

DISCUSSION

This study suggests that the validity of newer field and laboratory methods for estimation of body composition is poor in adolescent boys. For applications where high accuracy of estimation at the individual level is essential, only reference methods would be acceptable.

Bioimpedance vector pattern in cancer patients without disease versus locally advanced or disseminated disease

OBJECTIVE

Bioelectrical impedance vector analysis allows non-invasive evaluation of soft tissue hydration and mass through pattern analysis of vector plots as height, normalized resistance, and reactance measurements.

METHODS

Whole-body impedance measurements were made with a single frequency (50 kHz) analyzer (BIA-101, Akern/RJL Systems) in 148 adult, white, male subjects 45 to 85 y old: 56 healthy control subjects, 31 cancer patients after surgical procedure (without disease), and 61 patients with locally advanced (30 patients) or disseminated (31 patients) disease with the same body mass index and age. All patients were free from antineoplastic treatment and active nutritional intervention.

RESULTS

Mean vectors of cancer groups without disease and locally advance disease versus the control group were characterized by a comparable normalized resistance component with a reduced reactance component (separate 95% confidence limits, P < 0.05), indicating a comparable ionic conduction (hydration) with loss of dielectric mass (cell membranes and tissue interfaces) of soft tissues. Overlapping 95% confidence limits of their mean vectors indicated comparable electrical tissue properties in less versus more advanced disease.

CONCLUSION

Monitoring vector displacement trajectory toward the reference target vector position may represent useful feedback in support therapy planning of individual patients.

Estimation of the proportion of body fat in mice from the proportion of body water

We compared the proportion of body fat in mice as measured by chemical analysis with that estimated from the proportion of body water. First, we measured the proportion of fat by chemical analysis in 78 mice that had a proportion of body fat in the range from approximately 5 to 20%. Then, we constructed a regression line that described the relationship between the proportion of body water and the proportion of body fat by using data from several other published studies in mice (% body fat = -1.20 x % body water + 88.07, r = 0.9597, sy.x = 2.75, p < 0.001). With this regression line, we estimated the proportion of body fat from the proportion of body water that was measured by drying the carcasses at 60 degrees C for 3 days. Body fat data obtained from this regression line were similar to those obtained by chemical analysis. Thus, these results suggest that reliable values for the proportion of body fat can be derived from the proportion of body water and this method provides a tool to rapidly measure the proportion of body fat in mice.

Chemical body composition of 20 Thoroughbred foals at 160 days of age, and preliminary investigation of techniques used to predict body fatness

AIMS

To determine the chemical body composition of Thoroughbred foals born in two consecutive years, and to investigate several techniques used to predict body composition in foals born in the second year, with particular reference to fat.

METHODS

The chemical composition of 20 foals at around 160 days of age, born in two years, was determined. In vivo techniques to predict body composition were assessed in 23 foals born in Year 2, before and after euthanasia; 10 of these foals were used for chemical body composition analysis. Techniques to assess body composition in vivo included liveweight (LW), overall and regional condition scores, ultrasonic fat thickness measurements over the ribs and rump, linear measurements and bioelectrical impedance analysis. Correlations were determined between ultrasonic fat thickness, and bioelectrical impedance analysis, before and after euthanasia. Stepwise regression analysis was used to determine the relationships between in vivo techniques used to assess body composition and the chemical body composition of 10 animals.

RESULTS

Foals used for analysis of chemical composition weighed between 220.5 and 260.0 kg before euthanasia. Fat content ranged from 5.5-13.0% of the partial empty bodyweight (LW less head, gastrointestinal contents, distal limbs and skin). Fillies had significantly more fat mass and percentage fat than colts (p=0.031 for both measurements). The mean chemical composition of the fat-free partial empty body was 73.2% (SD 0.6) water, 22.7% (SD 0.9) protein, and 4.1% (SD 0.4) ash. Most of the variation in the concentration of empty body water was associated with variation in the concentration of fat (p<0.001). The live animal overall condition scores were correlated with fat mass and concentration (p=0.006 and p=0.013, respectively; n=10). Condition score over the rib region was highly correlated with fat mass and fat concentration (p=0.004 and p<0.001; n=10). Ultrasound measurements taken 10 cm cranial to the tailhead and 4 cm from midline, used to assess the thickness of rump fat, were correlated with condition score (p=0.001), and explained 71% of the variation in body fat mass (p=0.002; n=10).Nearly 50% of the variation in fat-free mass and partial empty body water mass were associated with variation in the impedance indices calculated from length and bioelectrical impedance analysis measurements (p=0.023 and p=0.026, respectively; n=10).

CONCLUSIONS

At around 42% of expected mature weight, fillies were significantly more fat than colts. Condition scores were correlated with partial empty body fat mass, and there was a trend for higher scores in fillies compared to colts. Much of the variation in water or protein mass of the partial empty body could be explained by variations in LW.

CLINICAL RELEVANCE

Measurements of LW, rump fat and condition score are useful predictors of the chemical composition of foals at 5 months of age.

Effects of gender, anthropometric variables, and aging on the evolution of hip strength in men and women aged over 65

Although gender differences in fall rates may partly explain the higher prevalence of fractures in elderly women than men, male bones may also be intrinsically stronger or suffer less structural degradation with age than those of women. We used hip structural analysis (HSA) to study gender differences in hip geometry and bone mineral density (BMD) as they evolved over time in elderly white men and women with the aim of identifying candidate biological pathways leading to heightened risk of hip fracture. We recruited 443 women and 439 men aged 67-79 years from a diet and cancer prospective population-based cohort study to a study of hip bone loss. Hip BMD was measured on two occasions 2-5 years apart by dual-energy X-ray absorptiometry and HSA software used to derive BMD and structural parameters at the narrow neck (NN), the intertrochanter (IT), and the shaft (S) regions. Structural indices calculated in each region were cross-sectional area (CSA)-amount of bone surface area in the cross section after excluding soft tissue space; section modulus (Z)-an index of bending resistance, subperiosteal width, endocortical width, cortical thickness; and cortical buckling ratio (CBR)-a measure of cortical instability. Compared to men, women had lower values of BMD, CSA, Z, subperiosteal width, endocortical width, and cortical thickness in all regions, except S endocortical width, after adjusting for weight, height, and age (P < 0.0001). CBR was higher in women than in men (P < 0.0001) in all regions. Longitudinal analysis of rates of change revealed faster rates of BMD decline in women than in men at the Hologic total hip, Hologic femoral neck, and IT regions (P < 0.029). Women had faster rates of subperiosteal and endosteal expansion than men at the NN (P < 0.011) and IT (P < 0.049) and faster increase in Z at the NN (P = 0.029). At the IT region, cortical thinning was faster in women than in men (P = 0.037) and CBR increased at a faster rate in women (P = 0.011). In conclusion, Z is lower in women than in men and expansion of the proximal femur occurs in both sexes, being faster in women than in men. Z does not decline at the same rate as BMD, implying that part of the effect of aging on BMD is due to expansion of the bony envelope without loss of bone mineral content. Faster expansion in the female femoral neck may in turn lead to greater fragility if wider diameter and thinner cortices become locally unstable.

A new air displacement plethysmograph for the measurement of body composition in infants

ABSTRACT This article introduces and evaluates the PEA POD Infant Body Composition System, an air displacement plethysmograph designed for the assessment of body composition in infants between birth and 6 mo of age. The performance of the PEA POD was evaluated by repeated testing of National Institute of Standards and Technology-traceable weights and volumes. Mass was measured in a single session. Volume was measured in four sessions during a 2-d period (five times/session for both). The mean values for repeated mass measurements were almost identical to the masses of traceable weights. The SD and CV for repeated volume measurements were 1.1-4.5 mL and 0.02-0.09%, respectively. Both the mean SD and CV were within very narrow ranges (1.4-3.1 mL for SD and 0.03-0.08% for CV) across all volume levels. Furthermore, mean CV values using results from the four sessions indicated excellent within- and between-day reliability. Regression analyses (by session or with all sessions combined) of the measured volume against actual volume gave very low standard error of the estimate (SEE) (0.853-1.957 mL) and very high R(2) (1.000), with the intercept and slope not significantly different from 0 and 1, respectively. The mean percentage error in volume measurements was < or =0.05% at all volume levels. The study findings and the operational and physical characteristics of the system indicate that the PEA POD has the potential to provide clinicians and researchers with a diagnostic and research tool that is accurate, easily used by operators, and comfortable for subjects.

Lithium target performance evaluation for low-energy accelerator-based in vivo measurements using gamma spectroscopy

The operating conditions at McMaster KN Van de Graaf accelerator have been optimized to produce neutrons via the (7)Li(p, n)(7)Be reaction for in vivo neutron activation analysis. In a number of earlier studies (development of an accelerator based system for in vivo neutron activation analysis measurements of manganese in humans, Ph.D. Thesis, McMaster University, Hamilton, ON, Canada; Appl. Radiat. Isot. 53 (2000) 657; in vivo measurement of some trace elements in human Bone, Ph.D. Thesis. McMaster University, Hamilton, ON, Canada), a significant discrepancy between the experimental and the calculated neutron doses has been pointed out. The hypotheses formulated in the above references to explain the deviation of the experimental results from analytical calculations, have been tested experimentally. The performance of the lithium target for neutron production has been evaluated by measuring the (7)Be activity produced as a result of (p, n) interaction with (7)Li. In contradiction to the formulated hypotheses, lithium target performance was found to be mainly affected by inefficient target cooling and the presence of oxides layer on target surface. An appropriate choice of these parameters resulted in neutron yields same as predicated by analytical calculations.

Detection of cardiovascular risk factors by indices of obesity obtained from anthropometry and dual-energy X-ray absorptiometry in Japanese individuals

OBJECTIVE

To determine the cut-off points of indices of obesity for detecting hypertension, dyslipidemia and diabetes mellitus in Japanese individuals.

DESIGN

Cross-sectional study.

SUBJECTS

A total of 2728 Japanese individuals (768 males and 1960 females, aged 20-79 y) who attended the Fukuoka Health Promotion Center, Japan for health check-up.

MEASUREMENTS

Body mass index (BMI), waist circumference (WC) and waist-hip ratio (WHR) were measured. Percentage fat mass (%FM), trunk fat mass (FM(trunk)) and trunk fat mass-leg fat mass ratio (FM(trunk)/FM(legs)) were obtained by dual-energy X-ray absorptiometry (DXA). Cardiovascular risk factors were determined by blood pressure, serum lipids, fasting blood glucose and hemoglobin A(1C).

RESULTS

The cut-off points of BMI, WC and WHR were around 23.5 kg/m(2), 84 cm and 0.9 for males, and 22.5 kg/m(2), 72 cm and 0.8 for females. The cut-off points of %FM, FM(trunk) and FM(trunk)/FM(legs) were around 24%, 8 kg and 1.6 for males, and 35%, 9 kg and 1.4 for females. WHR and FM(trunk)/FM(legs) most accurately detected the risk factors.

CONCLUSIONS

For Japanese individuals, the cut-off points for detecting cardiovascular risk factors are lower than the criteria by the World Health Organization. Indices of fat distribution detected the cardiovascular risk factors more accurately than those of overall adiposity. The accuracy of detecting the risk factors was comparable between the anthropometric indices and indices obtained by DXA.

Minor impact of juvenile arthritis on nutritional status in young adult patients

OBJECTIVE

Growth abnormalities and poor nutritional status have been reported in children with juvenile idiopathic arthritis (JIA). The aim of this study was to evaluate the impact of juvenile chronic rheumatic disease on current nutritional status in adult patients in remission or with active disease.

METHODS

One hundred thirty-eight women and 82 men, aged >20 years, with JIA were studied after a mean disease duration of 15.5 +/- 2.3 years. Eighty-four (61%) of the women and 49 (60%) of the men were in remission. Forty-one healthy women and 54 healthy men served as a reference group. Body composition was analyzed by dual-energy x-ray absorptiometry.

RESULTS

There was no difference in height or body mass index (BMI) between patients and healthy subjects. However, female patients with systemic disease had significantly reduced BMI compared with those with pauciarticular JIA (P < 0.001), and female patients who used or had been using corticosteroids had significantly lower weight, height, and BMI compared with the patients who had never used corticosteroids (P < 0.05). Female patients in remission had significantly more lean body mass compared with healthy controls (P < 0.05) and significantly less body fat was found in both women and men (P < 0.01 for both). Patients with active disease had the same amount of lean body mass as the healthy controls, but significantly less body fat (P < 0.05 for women and P < 0.01 for men).

CONCLUSION

Adult patients with JIA had attained normal height, weight, and BMI, with the exception of women with systemic JIA and those who were using or had used corticosteroids. Patients with JIA in remission seemed to have a better nutritional status than healthy subjects.

Sequential changes of body composition in patients with enterocutaneous fistula during the 10 days after admission

AIM: To investigate the sequential changes of body composition in the metabolic response that occurred in a group of patients with enterocutaneous fistula after admission to the hospital.

METHODS: Sixty-one patients with enterocutaneous fistula admitted to our hospital had measurements of body composition by multiple-frequency bioelectrical impedance analysis after admission and 5, 10 days later. Sequential measurements of plasma constitutive proteins were also made.

RESULTS: The body weight, fat-free mass, body mass index, and body cell mass were initially well below the normal range, especially the body mass index and body cell mass. And all the data gradually moved up over the 10-day study period, only a highly significant difference was found in body cell mass. Once the patients received nutrition supplement, ECW began to return to normal range slowly as well as ICW and TBW began to rise up, and ECW/TBW significantly declined to near normal level by day 10 in either male or female patients. There was a reprioritization of plasma constitutive protein synthesis that was obligatory and independent of changes in FFM.

CONCLUSION: Serial measurements can quantify the disturbance of body composition in enterocutaneous fistula patients. The early nutritional intervention rapidly ameliorates the abnormal distribution of body water while the state-of-the-art surgical management prevents the further deterioration in cellular composition.

Effects of rope-jump training on the os calcis stiffness index of postpubescent girls

PURPOSE

The specific aims of the study were to 1) determine what effects dose-dependent rope jumping had on os calcis stiffness index (OCSI) and 2) determine whether OCSI values measured by quantitative ultrasound (QUS) were dependent or independent of the values of bone mineral content (BMC) determined by dual energy x-ray absorptiometry (DXA) at the lumbar spine and proximal femur (femoral neck; greater trochanter).

METHODS

Upon study entry, girls were randomly assigned to either one of two treatment groups (high volume; low volume) or a control group. Thirty-seven high school girls were recruited to participate in the study. QUS and DXA measurements were made at baseline and at 4-month follow-up. Students in the high-volume and low-volume groups jumped rope for 10 and 5 min, respectively.

RESULTS

The follow-up mean OCSI values for the high-volume, low-volume, and control conditions were 103.95 +/- 12.55, 102.09 +/- 12.70, and 99.05 +/- 9.84, respectively. A statistically significant difference (P = 0.033) was identified between the high-volume and control groups. Baseline and follow-up OCSI values were significantly correlated with baseline and follow-up BMC measures of the femoral neck (r = 0.60, r = 0.59), greater trochanter (r = 0.47, r = 0.40), and lumbar spine (r = 0.56, r = 0.56).

CONCLUSIONS

High-volume rope jumping increases the OCSI more than the control condition in postpubescent girls. Furthermore, the OCSI measured by QUS is moderately related to proximal femur and lumbar spine BMC measured by DXA.

Establishing body composition in obesity

The field of human body composition research is reaching a mature stage in its development. Quantifying the main body components is integral to the study of growth, as the assessment of human physical characteristics is important both in anthropological and medical fields. This article will focus on body composition methodology. Specifically, our attention is aimed at estimates of body fatness. An overview is first provided of the five-level model of body composition as it relates to measures of fatness. We then provide general concepts related to techniques for estimating body composition. Finally, we briefly discuss the measurement of adipose tissue distribution.

Concurrent validity of the BOD POD and dual energy x-ray absorptiometry techniques for assessing body composition in young women

The purpose of this study was to determine the concurrent validity of the BOD POD (BP) (Life Measurement Instruments) and Dual Energy X-Ray Absorptiometry (DXA) Elite 4500A (Hologic, Inc.) techniques for assessing the body fat percentage of young women. The participants were forty-three white college-aged women (19.4 +/- 1.4 years) with a BMI of 23.4 +/- 2.3. Both body composition analyses were completed on the same day and were taken within 10 minutes of each other. Body fat percentage was estimated to be 24.3 (SE = 1.1) and 23.8 (SE = 0.8) using the BP and DXA techniques, respectively. Exact matches, in terms of body fat percentage, were obtained for 10 of the 43 participants (23.3%). In conclusion, our data supports the concurrent validity of the BP and DXA techniques for assessing body fat in young women.

Disease management of Prader-Willi syndrome

Prader-Willi Syndrome (PWS), first described in 1956, is a unique genetic condition with a prevalence of 1 in 10,000 - 25,000. Features include severe lifelong hypotonia, insatiable appetite, short stature, obsessive-compulsive behaviour, morbid obesity, hypogonadism, kyphosis, scoliosis and osteoporosis. Studies beginning in the 1970s demonstrated that PWS is associated with a deficiency in growth hormone. Growth hormone treatment in children with PWS improves linear growth and more importantly leads to an increased muscle mass, bone mineral density and physical performance. In mid-2000, growth hormone became the first pharmaceutical approved in the US and Europe for the treatment of childhood PWS. It is now considered an essential part of comprehensive care for this condition. Ongoing studies address issues of growth hormone dosage, long-term efficacy, effects on neonatal and childhood growth and development and effects in adults with PWS.

Assessment by bioimpedance of forearm cell mass: a new approach to calibration

OBJECTIVE

Changes in skeletal muscle mass are involved in several important clinical disorders including sarcopenia and obesity. Unlike body fat, skeletal muscle is difficult to quantify in vivo, particularly without highly specialized equipment. The present study had a two-fold aim: to develop a regional (40)K counter for non-invasively estimating cell mass in the arm, mainly skeletal muscle cell mass, without radiation exposure; and to test the hypothesis that cell mass in the arm is highly correlated with electrical impedance after adjusting for the arm's length.

METHODS

Forearm cell mass was estimated using a rectangular lead-shielded (40)K counter with 4-NaI crystals; impedance of the arm was measured at multiple frequencies using a segmental bioimpedance analysis (BIA) system. The system's within- and between-day coefficient of variation (CV) for (40)K-derived elemental potassium averaged 1.8+/-1.3 and 5.8+/-1.2%, respectively. The corresponding BIA system's CVs were 1.0+/-0.4 and 2.1+/-1.0%, respectively.

SUBJECTS AND RESULTS

Participants in the study were 15 healthy adults (eight females, seven males; age 39+/-2.8 y, BMI 22.9+/-4.5 kg/m(2)). The right arm's K (5.2+/-1.7 g) was highly correlated with length-adjusted impedance (r(2)=0.81, 0.82, and 0.83 for 5, 50 and 300 kHz, respectively; all P<0.001); multiple regression analysis showed no additional improvement by adding age or sex to the prediction models.

CONCLUSION

These results demonstrate the feasibility of calibrating BIA-measured electrical properties of the arm against estimates of arm cell mass, mainly of skeletal muscle, obtained by regional (40)K counting. This simple and practical approach should facilitate the development of BIA-based regional cell mass prediction formulas

Megestrol acetate stimulates weight gain and ventilation in underweight COPD patients

STUDY OBJECTIVES

To assess the effect of megestrol acetate (MA), a progestational appetite stimulant commonly used in patients with AIDS and cancer, on body weight and composition, respiratory muscle strength, arterial blood gas levels, and subjective perceptions in COPD patients.

DESIGN AND SETTING

Prospective, double-blind, randomized, placebo-controlled trial conducted on an outpatient basis at 18 sites.

PATIENTS

Underweight (< 95% ideal body weight) COPD patients > or = 40 years old.

INTERVENTIONS

Either MA, 800 mg/d oral suspension, or placebo at a 1:1 ratio for 8 weeks.

RESULTS

Of 145 randomized patients (63% men), 128 patients completed the trial. Body weight increased by 3.2 kg in the MA group and 0.7 kg in the placebo group (p < 0.001). Anthropometric and dual-energy radiograph absorptiometry assessments confirmed that weight gain was mainly fat. Spirometry and maximal voluntary ventilation showed no significant changes from baseline in either group, and the difference in the change in maximum inspiratory pressure between groups was not significant. The 6-min walk distances did not differ statistically between groups at week 2 and week 4, but were greater in the placebo group at week 8 (p = 0.012). Consistent with the known ability of MA to stimulate ventilation, PaCO(2) decreased (4.6 mm Hg, p < 0.001) and PaO(2) increased (2.8 mm Hg, p < 0.04) in the MA group. Questionnaires revealed that body image and appetite improved in the MA group but not the placebo group. Adverse event frequency and type were similar in both groups, but cortisol and testosterone (in men) levels decreased substantially in the MA group.

CONCLUSIONS

We conclude that MA safely increased appetite and body weight, stimulated ventilation, and improved body image in underweight COPD patients, but did not improve respiratory muscle function or exercise tolerance.

Peak VO2 correction for fat-free mass estimated by anthropometry and DEXA

PURPOSE

Anthropometric (ANTHRO) and dual-energy x-ray absorptiometric (DEXA) estimates of total body and leg fat-free masses (FFM) were obtained in 77 randomly selected sedentary men and women, aged 20-80: intermethod limits of agreement and their clinical significance, as inferred from the differences on peak VO2 corrected for FFMANTHRO and FFMDEXA, were determined.

METHODS

Limits of agreement were calculated as mean bias +/- 95% confidence intervals: peak VO2 at maximum cycle ergometry was related to FFMANTHRO and FFMDEXA by using both standard (y x x(-1)) and power function ratios (allometry).

RESULTS

Data distribution of the ANTHRO-DEXA differences presented significant heteroscedasticity in both sexes, i.e., differences were proportional to the mean (P < 0.05). After logarithmic transformation, the mean bias +/- 95% limits of agreement were expressed as ratios (ANTHRO x DEXA(-1) x// error ratio): these corresponded to 0.95 x// 1.11 or 0.99 x// 1.15 for total body FFM and 0.90 x// 1.10 or 1.02 x// 1.07 for leg FFM in men and women, respectively. In addition, we found different allometric exponents for FFMANTHRO and FFMDEXA: the intermethod differences, therefore, increased after power function expression (P < 0.05).

CONCLUSION

Discrepancies between ANTHRO and DEXA measurements of FFM depend on the magnitude of the estimate: differences are typically within 10 to 15%. Importantly, FFM-corrected peak VO2 values can vary according to the method chosen for body composition assessment, especially when allometry is used for peak VO2 correction. These results demonstrate that ANTHRO-DEXA differences in FFM estimation do have relevant practical consequences for the analysis of maximum aerobic capacity in nontrained humans.

Severity of human immunodeficiency virus infection is associated with decreased phase angle, fat mass and body cell mass in adults with pulmonary tuberculosis infection in Uganda

Although coinfection with tuberculosis and human immunodeficiency virus (HIV) is emerging as a major problem in many developing countries, nutritional status has not been well characterized in adults with tuberculosis and HIV infection. We compared nutritional status between 261 HIV-positive and 278 HIV-negative adults with pulmonary tuberculosis in Kampala, Uganda, using anthropometry and bioelectrical impedance analysis. Among 163 HIV-positive and 199 HIV-negative men, intracellular water-to-extracellular water (ICW:ECW) ratio was 1.48 +/- 0.26 and 1.59 +/- 0.48 (P = 0.006) and phase angle was 5.42 +/- 1.05 and 5.76 +/- 1.30 (P = 0.009), respectively. Among 98 HIV-positive and 79 HIV-negative women, ICW:ECW was 1.19 +/- 0.16 and 1.23 +/- 0.15 (P = 0.11) and phase angle was 5.35 +/- 1.27 and 5.43 +/- 0.93 (P = 0.61), respectively. There were no significant differences in BMI, body cell mass, fat mass or fat-free mass between HIV-positive and HIV-negative adults. Among HIV-positive subjects, BMI, ICW:ECW, body cell mass, fat mass and phase angle were significantly lower among those with CD4(+) lymphocytes < or = 200 cells/microL compared with those who had > 200 cells/microL. In sub-Saharan Africa, coinfection with pulmonary tuberculosis and HIV is associated with smaller body cell mass and intracellular water, but not fat-free mass, and by large differences in ICW:ECW and phase angle alpha.

Studies of a targeted risk reduction intervention through defined exercise (STRRIDE)

PURPOSE

The Studies of a Targeted Risk Reduction Intervention through Defined Exercise (STRRIDE) trial is a randomized controlled clinical trial designed to study the effects of exercise training regimens differing in dose (kcal.wk-1) and/or intensity (relative to peak VO2) on established cardiovascular risk factors and to investigate the peripheral biologic mechanisms through which chronic physical activity alters carbohydrate and lipid metabolism to result in improvements in these parameters of cardiovascular risk in humans.

METHODS

We will recruit 384 subjects and randomly assign them to one of three exercise training regimens or to a sedentary control group. The recruiting goal is to attain a subject population that is 50% female and 30% ethnic minority. The overall strategy is to use graded exercise training regimens in moderately overweight subjects with impairments in insulin action and mild to moderate lipid abnormalities to investigate whether there are dose or intensity effects and whether adaptations in skeletal muscle (fiber type, metabolic capacity, and/or capillary surface area) account for improvements in insulin action and parameters of lipoprotein metabolism. We will study these variables before and after exercise training, and over the course of a 2-wk detraining period. The study sample size is chosen to power the study to examine differences in responses between subjects of different gender and ethnicity to exercise training with respect to the least sensitive parameter-skeletal muscle capillary density.

RESULTS

The driving hypothesis is that improvements in cardiovascular risk parameters derived from habitual exercise are primarily mediated through adaptations occurring in skeletal muscle.

CONCLUSION

Identification that amount and intensity of exercise matter for achieving general and specific health benefits and a better understanding of the peripheral mechanisms mediating the responses in carbohydrate and lipid metabolism to chronic physical activity will lead to better informed recommendations for those undertaking an exercise program to improve cardiovascular risk.

Selected body composition methods can be used in field studies

This article provides an overview of the present status of in vivo body composition methodologies that have potential for use in field studies. The methods are divided into four general categories: anthropometric indices and skinfold, body volume measurements, body water measurements including bioelectrical methods, and imaging techniques. Among the newest technologies are air-displacement plethysmography, three-dimensional photonic scanning, multifrequency bioelectrical impedance spectroscopy and whole-body tomography using electrical impedance and magnetic induction. These newer approaches are compared with the established reference methods. The advantages and limitations of each technique as a field method are presented relative to the corresponding concepts of an ideal method.

Total-body-water measurement with 18O-labeled water in short-bowel patients with an ileostomy

The aim of this study was to evaluate the use of H(2)(18)O for total-body-water (TBW) determination in patients with short bowel because ileostomy losses of labeled water can falsify TBW. Thirteen adult short-bowel patients were studied after an overnight fast. Saliva, blood, urine and ileostomy output were collected before and 30, 60, 90, 120, 240, and 360 min after oral ingestion of 0.88 g/kg of 2.5% H(2)(18)O to measure (18)O abundance by isotope-ratio mass spectrometry. TBW was calculated from the dilution of the isotopic water in saliva and plasma. The quantity of labeled water lost in the ileostomy was calculated from the isotopic enrichment of the ileostomy output from T0 to T360. The values obtained from saliva or plasma with (corrected) and without (uncorrected) considering H(2)(18)O lost in the ileostomy output were compared with a paired t test. Agreement was evaluated using the Bland-Altman method. From T0 to T360, the ileostomy output and the percentage of lost labeled water were 490 +/- 314 mL and 6.38 +/- 8.52%, respectively. TBW calculated from plasma or saliva isotopic enrichment was different, and a significant difference was also observed between corrected and uncorrected TBW values (saliva: uncorrected TBW = 32.35 +/- 7.52 L, corrected TBW = 30.29 +/- 6.09 L; plasma; uncorrected TBW = 30.80 +/- 7.29 L, corrected TBW = 28.79 +/- 5.79 L). The agreement between the values obtained from the two dilution spaces or between the two calculation methods was poor. Because of the large discrepancies between calculation methods, determination of TBW from oral ingestion of (18)O-labeled water in patients with short bowel should be calculated only from plasma (18)O space dilution and should consider ileostomy losses.

Inactivation of the mouse melanocortin-3 receptor results in increased fat mass and reduced lean body mass

Genetic and pharmacological studies have defined a role for the melanocortin-4 receptor (Mc4r) in the regulation of energy homeostasis. The physiological function of Mc3r, a melanocortin receptor expressed at high levels in the hypothalamus, has remained unknown. We evaluated the potential role of Mc3r in energy homeostasis by studying Mc3r-deficient (Mc3r(-/-)) mice and compared the functions of Mc3r and Mc4r in mice deficient for both genes. The 4-6-month Mc3r-/- mice have increased fat mass, reduced lean mass and higher feed efficiency than wild-type littermates, despite being hypophagic and maintaining normal metabolic rates. (Feed efficiency is the ratio of weight gain to food intake.) Consistent with increased fat mass, Mc3r(-/-) mice are hyperleptinaemic and male Mc3r(-/-) mice develop mild hyperinsulinaemia. Mc3r(-/-) mice did not have significantly altered corticosterone or total thyroxine (T4) levels. Mice lacking both Mc3r and Mc4r become significantly heavier than Mc4r(-/-) mice. We conclude that Mc3r and Mc4r serve non-redundant roles in the regulation of energy homeostasis.