Assessing body composition with DXA and bioimpedance: effects of obesity, physical activity, and age

Prediction of fatness by standing 8-electrode bioimpedance: a multiethnic adolescent population

The objective of this study was to validate an 8-electrode bioimpedance analysis (BIA(8)) device (BC-418; Tanita, Tokyo, Japan) for use in populations of European, Maori, Pacific Island, and Asian adolescents. Healthy adolescents (215 M, 216 F; 129 Pacific Island, 120 Asian, 91 Maori, and 91 European; age range 12-19 years) were recruited by purposive sampling of high schools in Auckland, New Zealand. Weight, height, sitting height, leg length, waist circumference, and whole-body impedance were measured. Fat mass (FM) and fat-free mass (FFM) derived from the BIA(8) manufacturer's equations were compared with measurements by dual-energy X-ray absorptiometry (DXA). DXA-measured FFM was used as the reference to develop prediction equations based on impedance. A double cross-validation technique was applied. BIA(8) underestimated FM by 2.06 kg (P < 0.0001) and percent body fat (%BF) by 2.84% (P < 0.0001), on average. However, BIA(8) tended to overestimate FM and %BF in lean and underestimate FM and %BF in fat individuals. Sex-specific equations developed showed acceptable accuracy on cross-validation. In the total sample, the best prediction equations were, for boys: FFM (kg) = 0.607 height (cm)(2)/impedance ( ohm) + 1.542 age (y) + 0.220 height (cm) + 0.096 weight (kg) + 1.836 ethnicity (0 = European or Asian, 1 = Maori or Pacific) - 47.547, R(2) = 0.93, standard error of estimate (SEE) = 3.09 kg; and, for girls: FFM (kg) = 0.531 height (cm)(2)/impedance ( ohm) + 0.182 height (cm) + 0.096 weight (kg) + 1.562 ethnicity (0 = non-Pacific, 1 = Pacific) - 15.782, R(2) = 0.91, SEE = 2.19 kg. In conclusion, equations for fatness estimation using BIA(8) developed for our sample perform better than reliance on the manufacturer's estimates. The relationship between BIA and body composition in adolescents is ethnicity dependent.

Fat distribution influences the cardio-metabolic profile in a clinically healthy European population

BACKGROUND AND AIMS

Waist and hip circumferences are largely influenced by Fat Mass and several other determinants. To evaluate the specific effects of a preferential fat distribution, we corrected the waist and hip circumferences for all their determinants. We then examined the association between fat distribution and several cardio-metabolic parameters in a clinically healthy population.

SUBJECTS AND METHODS

In a subgroup of 625 females (F) and 490 males (M) from the RISC (Relationship between Insulin Sensitivity and Cardiovascular Disease) study, we evaluated insulin sensitivity by hyperinsulinaemic euglycaemic clamp and intima-media thickness (IMT) of the common (CCA) and internal (ICA) carotid artery by ultrasound imaging. Waist and hip circumferences were adjusted for age, height, fat and fat-free mass; in males, waist was also adjusted by hip and vice versa.

RESULTS

Both F and M with enlarged waist showed significantly increased plasma insulin, C-peptide, total cholesterol, non-high density lipoprotein-cholesterol, low density lipoprotein cholesterol and triglycerides, when compared with subjects with a smaller waist circumference. Males also showed lower glucose uptake and higher heart rate and ICA-IMT. A larger hip in both females and males was linked to a significantly greater inhibition of free fatty acids during the clamp test.

CONCLUSION

Adjustment of waist circumference for its determinants permits the detection of early impairment of cardiovascular function and of glucose and lipid metabolism in a clinically healthy population, in particular in normal body weight subjects. Enlarged hip adjusted values are associated with greater insulin sensitivity.

Estimates of body composition with dual-energy X-ray absorptiometry in adults

BACKGROUND

Little is known about the distributions of percentage body fat (PBF), total body fat (TBF), and fat-free mass (FFM) in the adult population in the United States.

OBJECTIVES

We sought to estimate the means and percentile cutoffs of PBF, TBF, and FFM and to assess the differences by sex, age, race-ethnicity, and body mass index in US adults.

DESIGN

Data from the National Health and Nutrition Examination Survey (NHANES), which were collected during the 6-y period from 1999 to 2004 and comprise a large nationally representative sample of the US population, were analyzed (n = 6559 men and 6507 nonpregnant women). TBF and FFM were measured by using dual-energy X-ray absorptiometry. PBF was calculated as TBF divided by total mass multiplied by 100.

RESULTS

There were large differences between men and women in unadjusted mean PBF (28.1% compared with 40.0%, P < 0.001), TBF (25.4 compared with 30.8 kg, P < 0.001), and FFM (62.3 compared with 44.0 kg, P < 0.001); the sex differences persisted across all body mass index categories after adjustment for age and race-ethnicity (all P < 0.001). The common percentile cutoffs of PBF, TBF, and FFM were estimated by sex, race-ethnicity, and age groups. Equations for the estimation of PBF (R(2) = 0.85), TBF (R(2) = 0.94), and FFM (R(2) = 0.94) according to demographic characteristics and simple anthropometric measures were generated.

CONCLUSION

The estimates of means and percentile cutoffs for PBF, TBF, and FFM, on the basis of NHANES 1999-2004 dual-energy X-ray absorptiometry data, provide a reference in the US adult population.

Value of the extracellular water ratio for assessment of cirrhotic patients with and without ascites

AIMS

Ascites, which often complicates liver cirrhosis, is reported to be a factor that worsens the outcome. The aims of this study were to quantify body water compartment changes in cirrhotic patients, with and without ascites, and to elucidate the value of body water analysis for predicting the development of ascites.

METHODS

A total of 109 cirrhotic patients, with and without ascites, and 65 controls were studied. Intra- and extracellular water (ECW) in the whole body and in the arm, leg and trunk were measured using the recently developed 8-electrodes multiple-frequency bioelectrical impedance analyzer. Furthermore, patients without ascites were followed to an episode of ascites or death.

RESULTS

Patients with liver cirrhosis had significantly higher ECW ratios than controls. ECW ratios were increased in cirrhotic patients with moderate and severe disease. The ECW ratio of the trunk showed highly significant changes in cirrhotic patients with ascites. The ECW ratio correlated with age, serum albumin, and prothrombin time. A relative expansion of ECW and low albumin were predictive of further episodes of ascites (log-rank 6.94, P < 0.01). In multivariate analysis, the ECW ratio was independently associated with the development of ascites.

CONCLUSION

Liver cirrhosis was characterized by a redistribution of body water. The ECW ratio is a reliable tool for quantification of redistribution of body water and can predict the development of ascites.

Combining near-subject absolute and relative measures of longitudinal hydration in hemodialysis

BACKGROUND AND OBJECTIVES

The feasibility and additional value of combining bioimpedance analysis (BIA) with near-subject absolute measurement of total body water using deuterium dilution (TBW(D)) in determining longitudinal fluid status was investigated.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Fifty-nine hemodialysis patients (17 female; age 58.4 +/- 16.1 yr; body mass index 27.0 +/- 5.4) were enrolled into a 12-mo, two-center, prospective cohort study. Deuterium concentration was measured in breath by flowing-afterglow mass spectrometry using a validated protocol ensuring full equilibration with the TBW; BIA was measured using a multifrequency, multisegmental device. Comorbidity was quantified by the Stoke score. Clinicians were blinded to body composition data.

RESULTS

At baseline and 12 mo, there was an incremental discrepancy between TBW(BIA) and TBW(D) volumes such that greater comorbidity was associated with increasing overhydration. Forty-three patients who completed the study had no longitudinal differences in the prescribed or achieved postdialysis weights. In contrast, TBW(D) increased without a change in TBW(BIA) (mean difference -0.10 L). Changes in TBW and lean body mass differed according to baseline comorbidity; without comorbidity, BIA also identified an increase in TBW and lean body mass, whereas with increasing comorbid burden, BIA failed to demonstrate increases in tissue hydration identified by TBW(D).

CONCLUSIONS

Combined near-patient measurements of absolute and BIA-estimated TBW are achievable in a dialysis facility by identifying changes in body composition not fully appreciated by routine assessment. BIA underestimates tissue overhydration that is associated with comorbidity, resulting in reduced sensitivity to longitudinal increases during a 12-mo period.

Body composition determination by bioimpedance: an update

PURPOSE OF REVIEW

To review various methods for measuring body composition by bioimpedance and their limitations, as well as available impedance meters, including body fat analyzers for home use.

RECENT FINDINGS

Bioimpedance spectroscopy, which requires multifrequency impedance meters, is preferable for fluid volume measurements, especially extracellular fluid, whereas bioimpedance analysis at 50 kHz is more widely used for measuring fat-free mass. A method for using bioimpedance spectroscopy equations with 50 kHz impedance meters has been recently proposed and successfully tested. Low cost foot-to-foot impedance meters (body fat analyzers) with plantar electrodes on a body scale, that are easy and fast to use, have been compared with medical impedance meters and with dual X-ray absorptiometry measurements and found reasonably accurate, except for individuals with very low or high BMI.

SUMMARY

Body composition by bioimpedance is gaining acceptance in nutrition, hemodialysis, gerontology and sports medicine. Body fat analyzers that have been validated by comparison with dual x-ray absorptiometry could be useful to general practitioners, nutritionists and cardiologists.

Risk of obesity in immigrants compared with Swedes in two deprived neighbourhoods

Background

Despite a strong social gradient in the prevalence of obesity, there is little scientific understanding of obesity in people settled in deprived neighbourhoods. Few studies are actually based on objectively measured data using random sampling of residents in deprived neighbourhoods. In addition, most studies use a crude measure, the body mass index, to estimate obesity. This is of concern because it may cause inaccurate estimations of the true prevalence and give the wrong picture of the factors associated with obesity. The aim of this study was to estimate the prevalence of, and analyse the sociodemographic factors associated with, three indices of obesity in different ethnic groups settled in two deprived neighbourhoods in Sweden.

Methods

Height and weight, waist circumference and body fat percentage were objectively measured in a random sample (n = 289). Sociodemographic data were obtained through a survey. Established cut-offs were used to determine obesity. Country of birth was categorized as Swedish, Other European, and Middle Eastern. Odds ratios were estimated by unconditional logistic regression.

Results

One third of the sample was classified as obese overall, with 39.0% of women being abdominally obese. After adjusting for age, we found higher odds of obesity in Middle Eastern women than in Swedish women regardless of outcome with odds ratios ranging between 2.74 and 5.53. Men of other European origin had higher odds of BMI obesity than Swedish men. Most associations between country of birth and obesity remained in the full model.

Conclusion

This study demonstrates the magnitude of the obesity problem and the need for prevention programmes targeting native and immigrant adults in deprived neighbourhoods in Sweden. The initiatives should also focus on particular groups, e.g. immigrant women and those experiencing economic difficulties. Further studies are needed on behavioural and environmental factors influencing the risk of obesity in residents settled in deprived neighbourhoods.

Measurements of body composition in limbs and trunk using a eight contact electrodes impedancemeter

Regional body composition measurements may be achieved in a single operation with impedancemeters equipped with four plantar and four hand electrodes. By measuring sequentially the resistances of five current lines connecting the hands and feet and solving a system of five linear equations, it is possible to calculate the resistances of each limb and the trunk. The impedancemeter used in this study was a prototype with four plantar electrodes and four additional contact electrodes for the hands. Its electronic hardware was identical to that of a Tefal commercial foot-to-foot impedancemeter (FFI). The Tefal FFI was used for measuring weight, whole body fat-free mass (FFM) and fat tissue mass (FM). Impedance and DXA measurements were taken sequentially on a 1st cohort of 170 healthy adults, aged from 19 to 75 years, to obtain equations relating appendicular FFM measured by DXA to their resistances, subject weight and height. For appendicular FM, correlations of the body FM measured by the FFI, age and BMI were used. Trunk FFM was obtained by subtracting appendicular FFM from FFM of trunk+limbs obtained by the same method as that for appendicular FFM. For an independent validation, these equations were tested on a 2nd cohort of 87 subjects (18-74 years) who underwent the same impedance and DXA protocol. Comparison of FFM and FM by impedance and by DXA in the limbs and the trunk using paired Student's t-tests, showed that they were not significantly different both in the 1st and validation cohorts. Mean FFM differences between impedance and DXA were -0.018+/-0.48 kg for right arms and -0.039+/-0.85kg for right legs of men in validation cohort. This work confirms that eight contact electrodes bioimpedance can measure appendicular and trunk FFM and FM in good agreement with DXA, at least in a healthy population.

Lower-limb pain, disease, and injury burden as determinants of muscle strength deficit after hip fracture

BACKGROUND

Hip fracture may result in an asymmetrical lower-limb strength deficit. The deficit may be related to the trauma, surgical treatment, pain, or disuse of the fractured limb. However, disease and injury burden or musculoskeletal pain in the other limb may reduce muscle strength on that side, reducing the asymmetrical deficit. The aim of our study was to explore the asymmetrical strength deficit and to determine the potential underlying factors in patients from six months to seven years after a hip fracture.

METHODS

The asymmetrical deficit was calculated ([fractured limb/sum of both lower limbs] x 100%) for isometric knee extension torque, rate of force development during isometric testing, and leg extension power. The asymmetrical measures for lower-limb muscle mass (fractured limb--nonfractured limb), and that of lower-limb pain and disease and injury burden (nonfractured limb--fractured limb), were calculated.

RESULTS

Half of the participants had no consistent asymmetrical deficit on the fractured side. Regression analyses showed that asymmetrical measures of lower-limb pain, muscle mass, and disease and injury burden predicted asymmetrical deficit in knee extension torque (R(2) = 0.43) and in the rate of force development (R(2) = 0.36). More intense pain and disease and injury burden affecting the nonfractured limb and smaller muscle mass relative to the fractured limb were associated with a smaller asymmetrical deficit.

CONCLUSIONS

Following a hip fracture, the prevention of decreases in muscle strength and power as well as a large asymmetrical deficit by the use of targeted pain management and rehabilitation may help to reduce the risk of subsequent mobility limitations and falls.

Postmenopausal hormone replacement therapy modifies skeletal muscle composition and function: a study with monozygotic twin pairs

We investigated whether long-term hormone replacement therapy (HRT) is associated with mobility and lower limb muscle performance and composition in postmenopausal women. Fifteen 54- to 62-yr-old monozygotic female twin pairs discordant for HRT were recruited from the Finnish Twin Cohort. Habitual (HWS) and maximal (MWS) walking speeds over 10 m, thigh muscle composition, lower body muscle power assessed as vertical jumping height, and maximal isometric hand grip and knee extension strengths were measured. Intrapair differences (IPD%) with 95% confidence intervals (CI) were calculated. The mean duration of HRT use was 6.9 ± 4.1 yr. MWS was on average 7% (0.9 to 13.1%, P = 0.019) and muscle power 16% (−0.8 to 32.8%, P = 0.023) greater in HRT users than in their cotwins. Thigh muscle cross-sectional area tended to be larger (IPD% = 6%, 95% CI: −0.07 to 12.1%, P = 0.065), relative muscle area greater (IPD% = 8%, CI: 0.8 to 15.0%, P = 0.047), and relative fat area smaller (IPD% = −5%, CI: −11.3 to 1.2%, P = 0.047) in HRT users than in their sisters. There were no significant differences in maximal isometric strengths or HWS between users and nonusers. Subgroup analyses revealed that estrogen-containing therapies (11 pairs) significantly decreased total body and thigh fat content, whereas tibolone (4 pairs) tended to increase muscle cross-sectional area. This study showed that long-term HRT was associated with better mobility, greater muscle power, and favorable body and muscle composition among 54- to 62-yr-old women. The results indicate that HRT is a potential agent in preventing muscle weakness and mobility limitation in older women.

Rheumatoid cachexia, central obesity and malnutrition in patients with low-active rheumatoid arthritis: feasibility of anthropometry, Mini Nutritional Assessment and body composition techniques

BACKGROUND AND AIMS

The concurrent decrease in fat free mass (FFM) and increase in fat mass (FM), including central obesity, in patients with rheumatoid arthritis (RA) may be related to increased cardiovascular morbidity as well as to functional decline. The objectives of this study were to evaluate body composition and nutritional status in patients with RA and the feasibility of bioelectrical impedance (BIA) to detect rheumatoid cachexia.

METHODS

Eighty RA outpatients (76% women), mean age 61 (range 22-80) years and with mean disease duration of 6 (range 1-52) years, were assessed by body mass index (BMI), waist circumference (WC), whole-body dual-energy X-ray absorptiometry (DXA), BIA and the Mini Nutritional Assessment (MNA).

RESULTS

Fat free mass index (FFMI; kg/m(2)) was low in 26% of the women and in 21% of the men. About every fifth patient displayed concomitant low FFMI and elevated fat mass index (FMI; kg/m(2)), i.e. rheumatoid cachexia. BMI and MNA were not able to detect this condition. Sixty-seven percent had increased WC. Reduced FFM was independently related to age (p = 0.022), disease duration (p = 0.027), ESR (p = 0.011) and function trendwise (p = 0.058). There was a good relative agreement between DXA and BIA (FM r (2) = 0.94, FFM r (2) = 0.92; both p < 0.001), but the limits of agreement were wide for each variable, i.e. for FM -3.3 to 7.8 kg; and for FFM -7.9 to 3.7 kg.

CONCLUSION

Rheumatoid cachexia and central obesity were common in patients with RA. Neither BMI nor MNA could detect this properly. There was a good relative agreement between DXA and BIA, but the limits of agreement were wide, which may restrict the utility of BIA in clinical practice.

Nutritional management of weight regain after bariatric surgery

BACKGROUND

The aim of this study was to propose dietetic guidelines for the nutritional management of weight regain in Roux-en-Y gastric bypass (RYGB) patients.

METHODS

Thirty patients more than 2 years after RYGB surgery were followed up once every 15 days for at least 3 months. We collected from the medical records weight before surgery, excess weight, minimum weight reached 2 years after surgery, and percent of body fat before the operation. Current weight and bioelectrical impedance analysis were assessed at every appointment. The prescribed diet had a low glycemic load with 45% of carbohydrates, 35% of protein (80 g for women and 100 g for men) and 20% of fat, three servings of dairy products, and a supplement of soluble fibers (15 g/day).

RESULTS

The patients had a previous average weight regain of 8 kg (+/-19). Forty percent of the sample had an excess weight loss (EWL) of less than 50%. After the intervention, 86% of the patients lost weight. The mean weight lost was 1.8 kg in the first month, 1.2 kg in the second month, and 1.3 kg in the third. Half of the sample with unsuccessful weight loss achieved an EWL of at least 50%. The failure rate of the group dropped from 40% to 20%. The percentage of body fat declined from 36.2% to 34% (p < 0.001).

CONCLUSION

Despite the short period of time, we observed that the nutritional counseling reduced the weight of patients with previous weight regain. There was also a reduction in body fat, which improves the perspective of weight maintenance in the future.