Dual-energy X-ray absorptiometry visceral adipose tissue estimates: reproducibility and impact of pre-assessment diet

The Benefits of Utilizing Total Body Composition as a Predictor of Cardiorespiratory Fitness Based on Age: A Pilot Study

Maximal oxygen consumption (VO2max) has been associated with body fat percentage (%BF) or fat free mass. However, most analyses do not consider total body composition (TBC) as defined by %BF, fat free mass index (FFMI—a height-adjusted measure of muscle mass), visceral adipose tissue, and bone mineral content (BMC). The aim of this study was to determine if TBC predicts cardiorespiratory fitness in healthy adults and if a relationship exists in young and older adults. Sixty healthy individuals (age group 1 (AG1, ≤35 years), n = 35; age group 2 (AG2, >35 years), n = 25) were screened in a cross-sectional study and retrospectively examined. All participants completed a full body DEXA scan and a standardized multistage treadmill test to determine VO2max. A multiple linear regression analysis was performed to examine the relationship between TBC and VO2max. The multiple regression model showed an overall significant effect for TBC (p < 0.001, R2 = 0.282). When analyzed by age group, the regression model of TBC was not significant in young adults (AG1, p = 0.319, R2 = 0.141), but significant in older adults (AG2, p < 0.001, R2 = 0.683). Significant predictors of VO2max in the older cohort were %BF (β = −0.748, p = 0.001) and BMC (β = 0.014, p = 0.002). Total body composition predicted VO2max in a small cohort of healthy adults. This study highlights the importance of TBC for cardiovascular health, especially in mid-to later-life individuals.

Precision of the Hologic DXA in the Assessment of Visceral Adipose Tissue

INTRODUCTION

Visceral fat, also known as visceral adipose tissue (VAT), has been the focus of intensive research over the past several yr, as ground breaking studies have investigated its possible role in predicting long-term cardiac dysfunction, hypertension, and diabetes. Historically, magnetic resonance imaging and computed tomography were the instruments of choice for visceral fat quantification. However, with the introduction of visceral fat assessment software for Dual-energy X-ray Absorptiometry (DXA) scanners, DXA's use for VAT assessment has become increasingly common. To effectively utilize DXA in future VAT research studies, information about their precision and accuracy must be known. This study provides novel information regarding the precision of the Hologic Horizon DXA scanner in the assessment of VAT.

METHODS

Sixty individuals (32.7 ± 17.1 yr, 51% male, 40% with body mass index (BMI) > 25 kg/m²) above the age of 16 years were recruited to participate in this study. Subjects found to be pregnant, have a lumbar vertebral compression fracture, nonremovable metal implants in the abdomen, or scoliosis/lordosis/kyphosis were excluded from the study. All subjects underwent 3 consecutive whole body scans on a Hologic Horizon A DXA scanner.

RESULTS

VAT mass ranged from 102 g to 1454 g. VAT precision improved with increasing BMI (p = 0.025): coefficient of variation (%CV) was 15.2% for underweight subjects (n = 2), 7.1% for healthy subjects (n = 34), 6.4% for overweight subjects (n = 18), and 4.7% for obese subjects (n = 6).

CONCLUSIONS

VAT measurement by Hologic DXA displays a satisfactory level of precision in individuals with a BMI of >18.5 kg/m². Precision was found to be higher in those with the greatest risk of cardio-metabolic dysfunction (individuals with high VAT). Due to its low cost, brief examination time, noninvasiveness, and limited radiation exposure, DXA may be considered the tool of choice for VAT determination in future studies.

Whole-body dual-energy X-ray absorptiometry demonstrates better reliability than segmental body composition analysis in college-aged students

Dual-energy X-ray absorptiometry (DXA) is rapidly becoming more accessible and popular as a technique to monitor body composition. The reliability of DXA has been examined extensively using a number of different methodological approaches. This study sets up to investigate the accuracy of measuring the parameters of body composition (BC) by means of the whole-body and the segmental DXA method analysis with the typical error of measurement (TEM) that allows for expressing the error in the units of measure. The research was implemented in a group of 63 participants, all of whom were university students. Thirty-eight males (22.6±2.9 years, average body mass 77.5±8.4 kg) and 25 females (21.4±2.0 years, average body mass 58.6±7.2 kg) were recruited. The measured parameters included body mass (BM), fat-free mass (FFM), body fat (BF), bone mineral content (BMC), bone mineral density (BMD). For the whole-body analysis, the determined TEM was: BM at the level of 0.12 kg in females and 0.29 kg in males; BF 0.25kg and 0.44% females, 0.52 kg and 0.66% males; FFM 0.24 kg females and 0.42 kg males; BMC 0.02 kg females and males; BMD 0.01g/cm2 females and males. The TEM values in the segmental analysis were: BF within the range of 0.04-0.28 kg and 0.68-1.20% in females, 0.10-0.36 kg and 0.72-1.94% in males; FFM 0.08-0.41 kg females and 0.17-0.86 males, BMC 0.00-0.02 kg females and 0.01-0.02 kg males in relation to the body segment (upper limb, trunk, lower limb). The BMD value was at the level of 0.01-0.02g/cm2. The study results showed high reliability in measuring body composition parameters using the DXA method. The whole-body analysis showed a higher accuracy of measurement than the segmental. Only the changes that are greater than the TEM, or the upper bound (95%) of the confidence interval of the measurement can be considered demonstrable when interpreting repeated measurements.