Seven-site versus three-site method of body composition using BodyMetrix ultrasound compared to dual-energy X-ray absorptiometry.

Obesity is a steadily growing epidemic affecting all segments of the population including college-aged students. The weight gain that is evidenced amid the transitional stage of college years increases the risks associated with cardiovascular and metabolic diseases. The BodyMetrix® BX-2000 (ULTRA) using a seven-site method has been evaluated against dual-energy X-ray absorptiometry (DXA) for estimation of body composition, which has yielded conflicting results. To date, no studies have compared the three-site method Jackson and Pollock three-site method to DXA. PURPOSE: The purpose of the study was twofold (i) to compare agreement between Jackson-Pollock seven site (JP7), Jackson-Pollock three site (JP3) and Pollock three site (P3) to predict body fat (%BF) using ULTRA and (ii) and to compare the three ULTRA methodologies against DXA. METHODS: Seventy-six healthy college-aged subjects (ages = 22·08 ± 2·50 years) participated in this study. DXA and ULTRA body composition assessments were performed following manufacturer's instructions to estimate %BF. Paired sample t-tests were used to assess agreement between JP7, P3 and JP3. Additionally, a two-tailed sample t-test was performed by sex. ULTRA and DXA results were also performed for agreement and bivariate correlation. RESULTS: No significant differences between JP7 and P3, P = 0·38, were observed. In males, no significant differences were observed between JP7 and P3, P = 0·18. Significant differences were observed in all other pairs, P≤0·001 and between ULTRA and DXA. CONCLUSIONS: The Pollock 3-site method estimates body fat percentage with comparable accuracy to JP7 using ULTRA.

A comparison of dual-energy X-ray absorptiometry, air displacement plethysmography and A-mode ultrasound to assess body composition in college-age adults.

BACKGROUND: There is currently a dearth of scientific literature exploring the agreement of A-mode ultrasound (US) body composition analysis with dual-energy X-ray absorptiometry (DXA) and air displacement plethysmography (ADP). OBJECTIVE: To investigate the agreement of US with DXA and ADP for estimating fat mass (FM) and fat-free mass (FFM). METHODS: College-age men (n = 33) and women (n = 41) volunteered to participate in this study. Participants were instructed to adhere to the following pretest protocol: refrain from food and drink 12 h prior to testing and wear tight fitting clothing. Body composition (BCA) was assessed using US, DXA and ADP in accordance with the respective manufacturer's guidelines. Two-way mixed-model AVOVA and Bland and Altman techniques were applied to explore agreement for FM and FFM among the three methods: US, ADP and DXA and by sex. RESULTS: There was no statistically significant effect by sex for either FM or FFM across all BCA comparisons (P = 0·504 and 0·510, respectively). US was not statistically different from ADP for FM and FFM (P ≈ 1·00). However, for FM and FFM, there were significant differences between DXA and both US and ADP (P≤0·001). The Bland and Altman analyses revealed large individual differences for all BCA. CONCLUSION: There was statistical agreement between US and ADP for FM and FFM but lack of agreement for US and ADP when compared to DXA. However, the large limits of agreement between methods warrant caution in generalizing these findings.

Comparison of air-displacement plethysmography results using predicted and measured lung volumes over a protracted period of time.

BACKGROUND: Air-displacement plethysmography (ADP) systems can either measure or predict lung volume (LV) in their test trials. The repeatability of the predicted and the measured value is an important factor in the accuracy of the final test result. OBJECTIVE: Compare the variability and accuracy of ADP tests using predicted and measured LV over a protracted period of time. METHODS: Twenty-four adults (18-30 years) participated in the study. Each subject underwent three ADP tests over a period of 3 weeks, with 1 week between tests. At each testing session, subjects were tested using a predicted LV protocol and a measured LV protocol in random order. LV, body volume (BV) and per cent body fat (% BF) were compared between testing modes and between assessment times. RESULTS: A two-way ANOVA examined the effect of the mode of LV assessment (measured or predicted) and trial (week) for LV and BV and the effect of the LV mode assessment (measured or predicted) and trial (week) on % BF results. LV and BV did not differ significantly (P>0.05) between the two modes of assessment (measured or predicted). Time (day of assessment) also was not significantly different between trials (P>0.05). Neither mode nor trial was significant (P>0.05), therefore neither had an effect on the % BF results. CONCLUSION: In this investigation, the method used to determine LV during ADP testing did not significantly affect the final % BF result. Also, tests performed over an extended period of time was not affected by LV measurement method.

Agreement between ultrasound and dual-energy X-ray absorptiometry in assessing percentage body fat in college-aged adults.

BACKGROUND: The BodyMetrix(®) BX-2000 Ultrasound device (ULTRA) shows prowess in being an effective alternative to the expense and technicality of dual-energy X-ray absorptiometry (DXA). However, this technique has not been investigated using a seven-site methodology. SUBJECT/OBJECTIVE: To employ a cross-over design to investigate the agreement between ULTRA using a seven-site methodology and DXA in assessing body fat (%BF) in a normal-weight sample of college-age men and women. METHODS: Subjects (n = 84, BMI = 23.6 ± 3.6 kg m(-²), age = 23.0 ± 4.7 years) participated in this study with %BF measurements following the manufacturer's specifications. RESULTS: Significant differences were observed between methods with ULTRA less than DXA (difference = 4.4 ± 0.8%, t-statistic = 7.27, P<0.001) with no difference between men and women. CONCLUSION: The current study showed that ULTRA using a seven-site methodology did not agree with DXA in measuring %BF. Thus, this investigational ULTRA methodology might not be appropriate in estimating %BF in this population.