Clinical utility and reproducibility of visceral adipose tissue measurements derived from dual-energy X-ray absorptiometry in White and African American adults

Evaluation of visceral adipose tissue thresholds for elevated metabolic syndrome risk across diverse populations: A systematic review

Beyond obesity, excess levels of visceral adipose tissue (VAT) significantly contribute to the risk of developing metabolic syndrome (MetS), although thresholds for increased risk vary based on population, regions of interest, and units of measure employed. We sought to determine whether a common threshold exists that is indicative of heightened MetS risk across all populations, accounting for sex, age, BMI, and race/ethnicity. A systematic literature review was conducted in September 2023, presenting threshold values for elevated MetS risk. Standardization equations harmonized the results from DXA, CT, and MRI systems to facilitate a comparison of threshold variations across studies. A total of 52 papers were identified. No single threshold could accurately indicate elevated risk for both males and females across varying BMI, race/ethnicity, and age groups. Thresholds fluctuated from 70 to 165.9 cm2, with reported values consistently lower in females. Generally, premenopausal females and younger adults manifested elevated risks at lower VAT compared to their older counterparts. Notably, Asian populations exhibited elevated risks at lower VAT areas (70-136 cm2) compared to Caucasian populations (85.6-165.9 cm2). All considered studies reported associations of VAT without accommodating covariates. No single VAT area threshold for elevated MetS risk was discernible post-harmonization by technology, units of measure, and region of interest. This review summarizes available evidence for MetS risk assessment in clinical practice. Further exploration of demographic-specific interactions between VAT area and other risk factors is imperative to comprehensively delineate overarching MetS risk.

Linear and non-linear relationships between body fat mass distribution and bone mineral density in adults: The NHANES, 2011-2018

OBJECTIVE

The relationship between body fat mass and bone mineral density (BMD) remains controversial. This research aimed to explore the linear or non-linear relationship between body fat mass and BMD among adults in the United States.

METHODS

This cross-sectional study identified adults aged 18 years or older in the National Health and Nutrition Examination Survey from 2011 to 2018. After adjusting for covariates, linear relationships between body fat mass and BMD in different genders were tested by generalized linear models, and potential non-linear relationships were explored by generalized additive models and piecewise linear regression models.

RESULTS

The research included 4691 (57.9% of the total sample) males and 3417 (42.1% the of total sample) females. In both males and females, we found a negative association between android or total body fat mass and lumbar spine BMD and a positive association between appendicular, android, gynoid, or total body fat mass and whole body BMD (all P < 0.05). The relationships between body fat mass in all regions and lumbar spine BMD were U-shaped in males and inverted U-shaped in females (all Pnon-linear < 0.05). Inverted U-shaped relationships existed between body fat mass in all regions and whole body BMD in females (all Pnon-linear < 0.05).

CONCLUSIONS

Body fat mass was negatively and linearly associated with lumbar spine BMD, but positively associated with whole body BMD. Body fat mass had a U-shaped relationship with lumbar spine BMD in males and an inverted U-shaped association with lumbar spine and whole body BMD in females.

Determination of body composition by dual x-ray absorptiometry in persons with haemophilia

BACKGROUND

There is limited research on body composition in persons with haemophilia (PwH). The literature describes an increased body fat distribution and decreased lean mass in PwH compared to healthy controls using bioimpedance analysis. Using dual x-ray absorptiometry (DXA), which is known to be the most accurate method, this investigation aims to postulate reference data for body composition parameters within haemophilia severity phenotypes and age groups.

METHODS

Persons underwent whole body DXA screening using Horizon. Body fat percentage, estimated visceral adipose tissue (VAT), appendicular fat and lean mass, and lean and fat mass in relation to body height were assessed. Haemophilia severity and five age groups were distinguished.

RESULTS

Two hundred and one persons with mild (n = 44), moderate (n = 41), or severe (n = 116) haemophilia A/B (median age 40 [28-55; 1.IQ-3.IQ] years) were analysed. The median body fat percentage was 28.7% [25.5%-33.9%] and median estimated VAT was 657 g [403-954 g] with no significant difference between severity phenotypes (p = .474; p = .781). Persons with severe haemophilia had less lean mass compared to moderate and mild haemophilia (p = .013; p = .034). Total and appendicular fat is increased in older PwH (aged ≥40 years) compared to younger PwH (aged ≤29 years; p < .05). Lean mass did not differ between age groups.

CONCLUSION

This study provides valuable reference data for body composition parameters in PwH. Persons with severe haemophilia show significantly less lean mass compared to persons with moderate or mild haemophilia. Body fat percentage and VAT did not differ between severity phenotypes, but increased with age.

Emergence of imaging technology beyond the clinical setting: Utilization of mobile health tools for at-home testing

Body composition assessment plays a pivotal role in understanding health, disease risk, and treatment efficacy. This narrative review explores two primary aspects: imaging techniques, namely ultrasound (US) and dual-energy x-ray absorptiometry (DXA), and the emergence of artificial intelligence (AI) and mobile health apps in telehealth for body composition. Although US is valuable for assessing subcutaneous fat and muscle thickness, DXA accurately quantifies bone mineral content, fat mass, and lean mass. Despite their effectiveness, accessibility and cost remain barriers to widespread adoption. The integration of AI-powered image analysis may help explain tissue differentiation, whereas mobile health apps offer real-time metabolic monitoring and personalized feedback. New apps such as MeThreeSixty and Made Health and Fitness offer the advantages of clinic-based imaging techniques from the comfort of home. These innovations hold the potential for individualizing strategies and interventions, optimizing clinical outcomes, and empowering informed decision-making for both healthcare professionals and patients/clients. Navigating the intricacies of these emerging tools, critically assessing their validity and reliability, and ensuring inclusivity across diverse populations and conditions will be crucial in harnessing their full potential. By integrating advancements in body composition assessment, healthcare can move beyond the limitations of traditional methods and deliver truly personalized, data-driven care to optimize well-being.

Changes in Lean Tissue Mass, Fat Mass, Biological Parameters and Resting Energy Expenditure over 24 Months Following Sleeve Gastrectomy

Sleeve gastrectomy (SG) induces weight loss but its effects on body composition (BC) are less well known. The aims of this longitudinal study were to analyse the BC changes from the acute phase up to weight stabilization following SG. Variations in the biological parameters related to glucose, lipids, inflammation, and resting energy expenditure (REE) were concomitantly analysed. Fat mass (FM), lean tissue mass (LTM), and visceral adipose tissue (VAT) were determined by dual-energy X-ray absorptiometry in 83 obese patients (75.9% women) before SG and 1, 12 and 24 months later. After 1 month, LTM and FM losses were comparable, whereas at 12 months the loss of FM exceeded that of LTM. Over this period, VAT also decreased significantly, biological parameters became normalized, and REE was reduced. For most of the BC, biological and metabolic parameters, no substantial variation was demonstrated beyond 12 months. In summary, SG induced a modification in BC changes during the first 12 months following SG. Although the significant LTM loss was not associated with an increase in sarcopenia prevalence, the preservation of LTM might have limited the reduction in REE, which is a longer-term weight-regain criterion.

Association of Abdominal Visceral Adiposity and Total Fat Mass with Cancer Incidence and Mortality in White and Black Adults

BACKGROUND

Race modifies the association between anthropometric measures of obesity and cancer risk. However, the degree to which abdominal visceral adipose tissue (VAT) and total fat mass (FM) are associated with cancer risk is not known.

METHODS

The sample included 3,017 White and 1,347 Black adults who were assessed between 1995 and 2016 and followed for outcome assessment through 2017. Abdominal VAT and FM were measured using imaging techniques. The co-primary endpoints were diagnosis of histologically confirmed invasive cancer (excluding nonmelanoma skin cancer) or death from cancer. Multivariable Cox proportional hazards models quantified the HR of incident cancer and cancer mortality.

RESULTS

There were 353 incident cancer cases and 75 cancer deaths in an average of 12.9 years of follow-up. Both VAT [HR, 1.21; 95% confidence interval (CI), 1.09-1.36] and FM (HR, 1.25; 95% CI, 1.10-1.43) were significantly associated with incident cancer, while VAT (HR, 1.28; 95% CI, 1.01-1.61) was significantly associated with cancer mortality after adjustment for several covariates. VAT remained significantly associated with cancer incidence (HR, 1.22; 95% CI, 1.03-1.46) after additional inclusion of FM in the multivariable model, but not vice versa. There were no significant sex- or race-interactions.

CONCLUSIONS

VAT was associated with risk of cancer and cancer mortality in this cohort, and the associations did not differ by sex or race. The association between VAT and incident cancer was largely independent of total FM.

IMPACT

Our results suggest that utility of anthropometry in assessing obesity-related cancer risk may need to be further refined by including more direct measures of adiposity.

Effect of high dose vitamin D supplementation on indices of sarcopenia and obesity assessed by DXA among older adults: A randomized controlled trial

BACKGROUND

Hypovitaminosis D is associated with Sarcopenic Obesity (SO), but evidence from randomized Vitamin D 3 (VD3) trials is scarce.

OBJECTIVE

Compare the effect of VD3 supplementation, at two doses, on SO indices at 12 months.

METHODS

Overweight older adults (>65 years) with baseline 25-hydroxyvitamin D (25OHD) of 10-30 ng/mL were recruited in this double-blind, randomized, controlled multicenter trial (clinicaltrial.gov identifier: NCT01315366). All subjects received 1000 mg calcium citrate/day and underwent total body Dual-energy X-ray Absorptiometry for body composition assessment. Low Dose Group (LDG) and High Dose Group (HDG) received 600 IU -Institute of Medicine (IOM) Recommended Dietary Allowance (RDA)- and 3750 IU VD3/day, respectively.

RESULTS

Mean age was 71 ± 4.6 years, 55% females, BMI: 30.2 ± 4.5 Kg/m², and 43% had metabolic syndrome. There were no differences in baseline characteristics between groups. At 12 months, 248 participants had body composition data, 122 in LDG and 126 in HDG. Proportions of patients with diminished muscle mass, muscle strength, and visceral adiposity did not differ between the 2 groups at baseline or 12 months. Similarly, no significant differences were noted in the proportion of patients with SO at study entry (1.8% in LDG vs 1.6% HDG; p = 0.99) and at 12 months (3.7% in LDG vs. 0.9% HDG; p = 0.18) across arms.

CONCLUSIONS

Weekly VD3, at the daily equivalent of 3750 IU/day, did not improve indices of sarcopenia nor adiposity compared to the IOM RDA dose in adults.

MRI Based Validation of Abdominal Adipose Tissue Measurements From DXA in Postmenopausal Women

INTRODUCTION

Visceral adipose tissue (VAT) is a hypothesized driver of chronic disease. Dual-energy X-ray absorptiometry (DXA) potentially offers a lower cost and more available alternative compared to gold-standard magnetic resonance imaging (MRI) for quantification of abdominal fat sub-compartments, VAT and subcutaneous adipose tissue (SAT). We sought to validate VAT and SAT area (cm2) from historical DXA scans against MRI.

METHODOLOGY

Participants (n = 69) from the Women's Health Initiative (WHI) completed a 3 T MRI scan and a whole body DXA scan (Hologic QDR2000 or QDR4500; 2004-2005). A subset of 43 participants were scanned on both DXA devices. DXA-derived VAT and SAT at the 4th lumbar vertebrae (5 cm wide) were analyzed using APEX software (v4.0, Hologic, Inc., Marlborough, MA). MRI VAT and SAT areas for the corresponding DXA region of interest were quantified using sliceOmatic software (v5.0, Tomovision, Magog, Canada). Pearson correlations between MRI and DXA-derived VAT and SAT were computed, and a Bland-Altman analysis was performed.

RESULTS

Participants were primarily non-Hispanic white (86%) with a mean age of 70.51 ± 5.79 years and a mean BMI of 27.33 ± 5.40 kg/m2. Correlations between MRI and DXA measured VAT and SAT were 0.90 and 0.92, respectively (p ≤ 0.001). Bland-Altman plots showed that DXA-VAT slightly overestimated VAT on the QDR4500 (-3.31 cm2); this bias was greater in the smaller subset measured on the older DXA model (QDR2000; -30.71 cm2). The overestimation of DXA-SAT was large (-85.16 to -118.66 cm2), but differences were relatively uniform for the QDR4500.

CONCLUSIONS

New software applied to historic Hologic DXA scans provide estimates of VAT and SAT that are well-correlated with criterion MRI among postmenopausal women.

Official Position of the Brazilian Association of Bone Assessment and Metabolism (ABRASSO) on the evaluation of body composition by densitometry-part II (clinical aspects): interpretation, reporting, and special situations

OBJECTIVE

To present an updated and evidence-based guideline for the use of dual-energy x-ray absorptiometry (DXA) to assess body composition in clinical practice.

MATERIALS AND METHODS

This Official Position was developed by the Scientific Committee of the Brazilian Association of Bone Assessment and Metabolism (Associação Brasileira de Avaliação Óssea e Osteometabolismo, ABRASSO) and experts in the field who were invited to contribute to the preparation of this document. The authors searched current databases for relevant publications in the area of body composition assessment. In this second part of the Official Position, the authors discuss the interpretation and reporting of body composition parameters assessed by DXA and the use of DXA for body composition evaluation in special situations, including evaluation of children, persons with HIV, and animals.

CONCLUSION

This document offers recommendations for the use of DXA in body composition evaluation, including indications, interpretation, and applications, to serve as a guiding tool in clinical practice and research for health care professionals in Brazil.

Accuracy of dual-energy x-ray absorptiometry for assessing longitudinal change in visceral adipose tissue in patients with coronary artery disease

BACKGROUND/OBJECTIVE

Visceral adipose tissue (VAT) is a key target of interventions for obesity-related diseases. Dual-energy x-ray absorptiometry (DXA) can estimate VAT, however its accuracy to measure longitudinal change in VAT compared to gold-standard techniques such as magnetic resonance imaging (MRI), has not been studied in adults. This study aimed to determine the accuracy of DXA compared with gold-standard MRI for cross-sectional VAT assessment, and for detecting longitudinal change in VAT.

METHODS

Adults with coronary artery disease (64 ± 8 years; BMI 27.8 ± 3.5 kg/m²; 88% male) were assessed for VAT by DXA and MRI at baseline (n = 34) and during implementation of an exercise intervention study at 3- and 12-months (n = 29). To match the 5.2 cm DXA measurement site for Hologic software (InnerCore^TM), VAT cross-sectional area (CSA) was measured by MRI using a single slice at L4/L5 junction, and VAT volume measured by 10 × 5 mm slices over the L4/L5 junction. MRI slices were quantified for VAT using semi-automated specialised software. Relationships between DXA and MRI for cross-sectional VAT and longitudinal change in VAT were determined by linear regression. Accuracy between the methods was assessed by Bland-Altman analysis, with data presented as mean difference (95% confidence interval), lower and upper limits of agreement (LoA).

RESULTS

Strong correlations were found between DXA-VAT and MRI-VAT at baseline (r = 0.90; p < 0.001), and longitudinal change in DXA-VAT and MRI-VAT over 3- and 12-months (r = 0.67; p < 0.001). In contrast, Bland-Altman analysis revealed significant overestimation by DXA-VAT volume at baseline by 13% [-104 cm³ (-157, -52 cm³), p < 0.001; LoA (-398, 189 cm³)], and underestimation of change in DXA-VAT volume over 3-months by 33% [-41 cm³ (-77, -4 cm³), p = 0.030; LoA (-228, 147 cm³)] and 12-months by 47% [-65 cm³ (-114, -17 cm³), p = 0.010; LoA (-316, 185 cm³)]. Results were similar for VAT CSA.

CONCLUSIONS

Compared with MRI, DXA substantially underestimated longitudinal changes in VAT. Therefore, DXA is not currently a valid alternative to MRI for quantifying VAT changes and may under-represent the effectiveness of interventions for obesity management.

Associations of DXA-measured abdominal adiposity with cardio-metabolic risk and related markers in early adolescence in Project Viva

BACKGROUND

Increased visceral adipose tissue (VAT) precedes development of insulin resistance and dyslipidemia in adults. The associations of abdominal adiposity derived from dual-energy X-ray absorptiometry (DXA), including VAT, subcutaneous abdominal adipose tissue (SAAT) and total abdominal adipose tissue (TAAT) with cardio-metabolic risk in adolescents are understudied.

OBJECTIVES

We examined the cross-sectional associations of DXA-measured abdominal adiposity with cardio-metabolic risk and related markers in early adolescence (mean [SD] age 13.0 [0.7] years).

METHODS

We collected data from 740 adolescents (374 girls and 366 boys) in Project Viva, a U.S. pre-birth cohort. We used DXA estimates of VAT, SAAT and TAAT area. We conducted overall and sex-stratified linear regression models, adjusting for age, sex (in overall models), race/ethnicity, puberty score and body mass index (BMI) z-score.

RESULTS

Mean BMI z-score was 0.59 (1.28). After adjustment, greater VAT (per 1 SD score) was associated with higher metabolic risk z-score (β 0.14 units; 95% CI 0.08, 0.20), higher log high-sensitivity C-reactive protein (β 0.51 mg/L; 0.36, 0.66) and log leptin (β 0.36 ng/mL; 0.27, 0.44), and lower log adiponectin (β -0.08 ug/mL; -0.13, -0.02). SAAT and TAAT showed similar associations as VAT with comparable or greater effect sizes.

CONCLUSION

In early adolescence, DXA-measured VAT, SAAT and TAAT are associated with cardio-metabolic risk and related markers, independent of current BMI. Among two adolescents with the same BMI, there is an associated higher cardio-metabolic risk in the adolescent with greater DXA-measured abdominal adiposity.

Age- and sex-specific visceral fat reference cutoffs and their association with cardio-metabolic risk

BACKGROUND

Although excess visceral fat (VAT) is associated with numerous cardio-metabolic risk factors, measurement of this fat depot has historically been difficult. Recent dual X-ray absorptiometry approaches have provided an accessible estimate of VAT that has shown acceptable validity against gold standard methods. The aims of this study were to (i) evaluate DXA measured VAT as a predictor of elevated blood lipids and blood pressure and (ii) calculate thresholds associated with these cardio-metabolic risk factors.

SUBJECTS/METHODS

The sample comprised 1482 adults (56.4% women) aged 18-66 years. Total body scans were performed using a GE Lunar Prodigy, and VAT analyses were enabled through Corescan software (v 16.0). Blood pressure and blood lipids were measured by standard procedures. Regression models assessed how VAT mass was associated with each cardio-metabolic risk factor compared to other body composition measures. Measures of sensitivity and specificity were used to determine age- and sex-specific cut points for VAT mass associated with high cardio-metabolic risk.

RESULTS

Similar to waist circumference, VAT mass was a strong predictor of cardio-metabolic risk especially in men over age 40. Four cut-offs for VAT mass were proposed, above which the cardio-metabolic risk increased: 700 g in women <40 yrs; 800 g in women 40+ yrs; 1000g in men <40 yrs; and 1200 g in men 40+ yrs. In general, these cut-offs discriminated well between those with high and low cardio-metabolic risk.

CONCLUSIONS

In both sexes, DXA measured VAT was associated with traditional cardio-metabolic risk factors, particularly high blood pressure in those 40+ yrs and low HDL < 40 yrs. These reference values provide a simple, accessible method to assess cardio-metabolic risk in adults.

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.

Baseline HOMA IR and Circulating FGF21 Levels Predict NAFLD Improvement in Patients Undergoing a Low Carbohydrate Dietary Intervention for Weight Loss: A Prospective Observational Pilot Study

Background: Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver disease. Very low-calorie ketogenic diets (VLCKD) represent a feasible treatment as they induce profound weight loss and insulin resistance (IR) improvement. Despite the recognized benefits on NAFLD deriving from pharmacological administration of fibroblast growth factor 21 (FGF21), whose endogenous counterpart is a marker of liver injury, little is known about its physiology in humans. Aim: To identify predictors of NAFLD improvement as reflected by the reduction of the non-invasive screening tool hepatic steatosis index (HSI) in obese patients undergoing a weight loss program. Methods: Sixty-five obese patients underwent a 90-day dietary program consisting of a VLCKD followed by a hypocaloric low carbohydrate diet (LCD). Anthropometric parameters, body composition, and blood and urine chemistry were assessed. Results: Unlike most parameters improving mainly during the VLCKD, the deepest HSI change was observed after the LCD (p = 0.02 and p < 0.0001, respectively). Baseline HOMA-IR and serum FGF21 were found to be positive (R = 0.414, p = 0009) and negative (R = 0.364, p = 0.04) independent predictors of HSI reduction, respectively. Conclusions: We suggest that patients with IR and NAFLD derive greater benefit from a VLCKD, and we propose a possible role of human FGF21 in mediating NAFLD amelioration following nutritional manipulation.

Inverse relationship between serum Metrnl levels and visceral fat obesity (VFO) in patients with type 2 diabetes

AIM

The relationship between serum Metrnl levels and visceral fat obesity (VFO) remains unclear. This study aimed to investigate the association between serum Metrnl levels and VFO in Chinese patients with type 2 diabetes.

METHODS

A total of 321 Chinese patients with type 2 diabetes (226 men and 95 postmenopausal women aged 61.4 ± 6.5 years, BMI 25.1 ± 3.2 kg/m²) were evaluated. Serum Metrnl levels were measured by enzyme linked-immunosorbent assay. Visceral fat area (VFA) was quantified via Dual Energy X-ray Absorptiometry (DXA). Correlation analyses were carried out for serum Metrnl levels and VFO.

RESULTS

VFO groups (VFA ≧100 cm²) have lower serum Metrnl levels than non-VFO groups (VFA < 100 cm²) (578.9 ± 225.1 vs. 684.9 ± 263.8, P = 0.001). An increasing trend in serum Metrnl levels was found to accompany the decrease in VFA. Serum Metrnl levels were negatively correlated with VFA, total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and albumin (ALB), but positively correlated with age, height, blood urea nitrogen (BUN), creatinine (Cr) and uric acid (UA) (all P < 0.05). Binary logistic regression analysis showed that serum Metrnl was inversely associated with VFO even after adjusted age, gender, height, TC, TG, LDL-C, ALB, BUN, Cr, and UA (odds ration [OR], 0.846; confidence interval [CI], 0.745-0.961; P = 0.010). The optimal cut-off value of serum Metrnl levels that predicted VFO was 671.3 ng/ml (95%CI = 0.55-0.70, P = 0.001).

CONCLUSIONS

Serum Metrnl levels were inversely correlated with VFO and may be a useful indicator of VFO in Chinese patients with type 2 diabetes.

Technological Advances in Diagnostic Imaging in Exotic Pet Medicine

Diagnostic imaging relies on interpretation of interactions between the body tissue and various energies, such as x-rays, ultrasound, and magnetic or nuclear energies, to differentiate normal from abnormal tissues. Major technological improvements regarding emission and detection of the energetic waves, as well as reconstruction and interpretation of the images, have occurred. These advances made possible visualization of smaller structures, quantitative evaluation of functional processes, and development of unique imaging-guided procedures. This article reviews the technological advances that allowed development of cone beam computed tomography, dual-energy x-ray absorptiometry, and contrast-enhanced ultrasonography, which all could have applications in exotic pet medicine.

Visceral adipose tissue normative values in adults from the United States using GE Lunar iDXA

OBJECTIVES

To create normative data for visceral adipose tissue (VAT) derived from the GE Lunar iDXA specific to sex and age cohorts for adults in the United States (US).

METHODS

A cross-sectional analysis of 649 adults were evaluated [Mean ± SD (Range): Males: n = 351; Age = 33·2 ± 17·4 years (18-75 years); Body mass index (BMI) = 26·5 ± 5·4 kg·m^-2 (17·5-44·2 kg·m^-2 ); Females: n = 298; Age = 28·5 ± 14·3 years (18·0-75·0 years); BMI=25·8 ± 6·9 kg·m^-2 (17·9-54·8 kg·m^-2 )]. From a total body dual-energy X-ray absorptiometry (DXA) scan, VAT mass (kg) and volume (cm³ ) were quantified from the software-delineated region-of-interest. The relationship between VAT and age was evaluated using regression analysis. Separate VAT percentiles were stratified by age range (18-19 years; 20-24 years; 25-50 years; 50+ years) for males and females.

RESULTS

In both males and females, there was a positive, non-linear relationship between VAT and age (R²  = 0·47-0·49; P<0·0001). In males, the 50th percentile for VAT mass and volume, stratified by age was: 18-19 years (0·18 kg; 185·67 cm³ ), 20-24 years (0·25 kg; 261·21 cm³ ), 25-49 years (0·71 kg; 746·27 cm³ ) and 50+ years (1·62 kg; 1708·36 cm³ ). In females, the 50th percentile for VAT mass and volume, stratified by age was: 18-19 years (0·04 kg; 44·90 cm³ ), 20-24 years (0·06 kg; 59·57 cm³ ), 25-49 years (0·55 kg; 579·28 cm³ ) and 50+ years (1·21 kg; 1284·59 cm³ ).

CONCLUSION

These normative values provide a reference for VAT mass and volume in US adults 18-75 years of age obtained using the GE Lunar iDXA. Measures of VAT provide important information about metabolic and cardiovascular health risk beyond that of BMI and per cent body fat.

Acute and longer-term body composition changes after bariatric surgery

BACKGROUND

Bariatric surgery induces weight loss but its acute and longer-term effects on body composition (BC) are largely unknown.

OBJECTIVES

To determine the BC changes in obese French patients after sleeve gastrectomy (SG) at 1 and 12 months.

SETTING

Obesity Reference Center, University Hospital of Montpellier, France.

METHODS

Whole and localized BC (lean tissue mass [LTM] and fat mass [FM]) and abdominal adiposity, including total adipose tissue, visceral adipose tissue, and subcutaneous adipose tissue, were determined by dual-energy X-ray absorptiometry in 30 obese patients (25 women, 83.3%) just before SG and 1 and 12 months later.

RESULTS

The mean weight loss was -9.7 ± 2.6 kg at 1 month and -32.1 ± 10.3 kg at 12 months. This weight loss was due to an equivalent decrease in LTM and FM in the acute phase, while FM loss appeared to be the main cause in the chronic phase. For each component (LTM and FM), the loss was relatively homogeneous across sites. Compared with the presurgical values, android and gynoid tissue and total adipose tissue, visceral adipose tissue, and subcutaneous adipose tissue changed significantly over the 12-month period. No basal clinical parameter was predictive of the variation in LTM, whereas age and the whole-body LTM/FM ratio were associated with the decrease in FM.

CONCLUSION

This study demonstrates that SG induces a clear modification in BC, characterized by a decrease in LTM in the acute phase and sustained FM loss in the first year. These results suggest that the early phase should be targeted for strategies to reduce LTM loss, which is a longer-term weight-regain criterion. Further studies to investigate the potential advantages of visceral adipose tissue compared with whole-body FM for improving post-SG co-morbidities should be performed.

Age- and sex-specific reference intervals for visceral fat mass in adults

BACKGROUND/OBJECTIVES

Dual-energy X-ray absorptiometry (DXA) is becoming a method of choice for the assessment of visceral adipose tissue (VAT) but the lack of robust reference ranges presents a challenge to the interpretation of VAT in clinical practice, research settings, and the athletic environment. The objective of this study was to develop age- and sex-specific reference intervals for DXA-derived VAT mass.

SUBJECTS/METHODS

The reference group comprised 3219 adults (1886 general population, 42% women; 1333 athletes, 11% women) in the United Kingdom, aged 18-83 years. Total body scans were performed using a GE Lunar iDXA and VAT analyses were enabled through Corescan software (Encore version 15.0). Age-specific reference ranges were derived in samples stratified by sex and general population/ athlete status. We modelled the mean and SD of Box-Cox transformed VAT mass as a function of age with a generalised least squares method using fractional polynomials (Stata® -xrigls- program). Centile values were then back-transformed to provide reference intervals on the original scale.

RESULTS

In general population samples, average VAT mass increases with age up until around 65-70 years, and then begins to decline at older ages, though data are relatively sparse at the upper end of the age range. In athletes, on average, VAT mass increases with advancing age in men and women. Both 95 and 98% reference ranges are presented in 5-year increments in all samples, and we provide equations to enable the calculation of any centile, for any age within the range.

CONCLUSIONS

These reference data can aid the interpretation of VAT mass specific to an individual's sex, age, and athletic status, increasing the utility and applicability of DXA-derived VAT assessments. Additional research is needed in adults over 65 years and female athletes, with different DXA devices, across different ethnic groups and specific sports.

Assessment of Body Composition in Health and Disease Using Bioelectrical Impedance Analysis (BIA) and Dual Energy X-Ray Absorptiometry (DXA): A Critical Overview

The measurement of body composition (BC) represents a valuable tool to assess nutritional status in health and disease. The most used methods to evaluate BC in the clinical practice are based on bicompartment models and measure, directly or indirectly, fat mass (FM) and fat-free mass (FFM). Bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DXA) (nowadays considered as the reference technique in clinical practice) are extensively used in epidemiological (mainly BIA) and clinical (mainly DXA) settings to evaluate BC. DXA is primarily used for the measurements of bone mineral content (BMC) and density to assess bone health and diagnose osteoporosis in defined anatomical regions (femur and spine). However, total body DXA scans are used to derive a three-compartment BC model, including BMC, FM, and FFM. Both these methods feature some limitations: the accuracy of BIA measurements is reduced when specific predictive equations and standardized measurement protocols are not utilized whereas the limitations of DXA are the safety of repeated measurements (no more than two body scans per year are currently advised), cost, and technical expertise. This review aims to provide useful insights mostly into the use of BC methods in prevention and clinical practice (ambulatory or bedridden patients). We believe that it will stimulate a discussion on the topic and reinvigorate the crucial role of BC evaluation in diagnostic and clinical investigation protocols.

Comparison of visceral fat measurement by dual-energy X-ray absorptiometry to computed tomography in HIV and non-HIV

Background/Objectives

Individuals with HIV are susceptible to visceral fat accumulation, which confers an increased risk of cardiometabolic disease. Advanced software to ascertain visceral fat content from dual-energy X-ray absorptiometry (DXA) has not been validated among this population. We sought to compare DXA with computed tomography (CT) in the measurement of visceral fat cross-sectional area (VAT) in HIV and non-HIV using Bland–Altman analyses.

Subjects/Methods

Data were combined from five previously conducted studies of individuals with HIV (n = 313) and controls without HIV (n = 144) in which paired DXA and CT scans were available. In cross-sectional analyses, DXA-VAT was compared with CT-VAT among participants with and without HIV. In longitudinal analyses, changes in VAT over time were compared between DXA and CT among participants with and without HIV receiving no intervention over 12 months and among individuals with HIV receiving tesamorelin—a medication known to reduce VAT—over 6 months.

Results

In HIV, DXA underestimated VAT compared with CT among individuals with increased visceral adiposity. The measurement bias was −9 ± 47 cm² overall, but became progressively larger with greater VAT (P < 0.0001), e.g., −61 ± 58 cm² among those with VAT ≥ 200 cm². Sex-stratified analyses revealed that the relationship between VAT and measurement bias was especially pronounced in men (P < 0.0001). Longitudinally, DXA underestimated changes in VAT, particularly among those at the extremes of VAT gain or loss (P < 0.0001). In contrast to the cross-sectional findings, the tendency for DXA to underestimate longitudinal changes in VAT was evident in both men and women. Analogous findings were seen among controls in cross-sectional and longitudinal analyses.

Conclusions

DXA underestimated VAT relative to CT in men with and without HIV, who had increased visceral adiposity. DXA also underestimated changes in VAT over time in men and women, irrespective of HIV status. DXA-VAT should be used with caution among both HIV and non-HIV-infected populations.

Correlation of body composition parameters using different methods among Brazilian obese adults

Abstract Data comparing anthropometric measurements, bioelectrical impedance analysis (BIA) and dual-energy X-ray absortiometry (DXA) parameters are somehow limited and conflicting. The objective of this study was to correlate anthropometric, BIA and DXA parameters among obese Brazilian adults with focus on the comparison with visceral adipose tissue (VAT) obtained from DXA and in the value of antropometric measurements. Fifty voluntary participants were enrolled. The Spearman correlation test was used to assess the correlation of VAT with anthropometric measurements, BIA and other DXA parameters. The intra-class correlation coefficient (ICC) was used to evaluate concordance between lean mass (LM), fat mass (FM), %body fat (%BF) and %upper body fat (%UBF) obtained from BIA and DXA. Most were female (80%) and had an average body index mass (BMI) of 39.0 (± 6.4) kg/m2. The only anthropometric measurements showing a strong correlation with VAT were abdominal circumference (AC) and waist-to-height ratio (WHtR), but just in females. There was a very good correlation for LM [ICC = 0.951 (CI = 0.913 - 0.972)], FM [ICC = 0.987 (CI = 0.977 – 0.993)], %BF [ICC = 0.961 (CI = 0.931-0.978)], and %UBF [ICC = 0.873 (CI = 0.776 – 0.928)], between data collected through BIA and DXA. Among the anthropometric measurements assessed, only AC and WHtR seems to estimate patients with abdominal fat distribution and higher VAT in females. DXA and BIA proved similar for the evaluation of LM, FM, %BF and %UBF, although DXA has the advantage of estimating VAT.

Correlation between DXA and laboratory parameters in normal weight, overweight, and obese patients

OBJECTIVE

The aim of this study was to review the existence and types of correlations between body composition densitometric parameters and laboratory values associated to cardiometabolic risk.

METHODS

We retrospectively analyzed data from 316 individuals in the weight range from normality to super-obesity, submitted to total body dual-energy x-ray absorptiometry (DXA) scans and routine biochemistry at S.Orsola-Malpighi Hospital from June 2010 to March 2014. The study included 182 women, 45.8 ± 13.4 y of age, with a body mass index (BMI) of 31.5 (± 11) kg/m² (group F) and 134 men, 45.4 ± 13.6 y of age, with a BMI of 27.6 (± 7.8) kg/m² (group M). All patients underwent whole-body scan (Lunar iDXA, GE Healthcare, Madison, WI, USA) and laboratory analysis (blood fasting glucose, total cholesterol, high-density lipoprotein cholesterol, tricylglycerides [TGs], aspartate aminotransferase, and alanine aminotransferase). Correlation between laboratory values and total body and regional fat mass (including visceral adipose tissue [VAT] and subcutaneous adipose tissue in the android region), and lean mass parameters were analyzed with linear and stepwise regressions analysis (significance limit, P < 0.05). Receiver operating characteristic curves were performed to assess the accuracy of the best-fit DXA parameter (VAT) to identify at least one laboratory risk factor.

RESULTS

In both groups, BMI and densitometric parameters showed a linear correlation with fasting blood glucose and TG levels and an inverse correlation with high-density lipoprotein cholesterol (P < 0.05), whereas no correlation was observed with total cholesterol levels. The only densitometric parameter retained in the final model of stepwise multiple regression was VAT for fasting blood glucose (group F: β = 0.4627, P < 0.0001; group M: β = 0.6221, P < 0.0001) and TG levels (group F: β = 0.4931, P < 0.0001; group M: β = 0.1990, P < 0.0261) independently of BMI. The optimal cutoff points of VAT to identify the presence of at least one laboratory risk factor were >1395 g and >1479 cm³ for men and >1281 g and >1357 cm³ for women.

CONCLUSIONS

DXA analysis of VAT is associated with selected laboratory parameters used for the evaluation of cardiometabolic risk and could be per se a helpful parameter in the assessment of clinical risk.

Body adiposity indicators and cardiometabolic risk: Cross-sectional analysis in participants from the PREDIMED-Plus trial

BACKGROUND & AIMS

Excess adiposity is associated with poor cardiometabolic (CM) health. To date, several techniques and indicators have been developed to determine adiposity. We aimed to compare the ability of traditional anthropometric, as well as standard and novel DXA-derived parameters related to overall and regional adiposity, to evaluate CM risk.

METHODS

Using the cross-sectional design in the context of the PREDIMED-Plus trial, 1207 Caucasian senior men and women with overweight/obesity and metabolic syndrome (MetS) were assessed. At baseline, anthropometry- and DXA-measured parameters of central, visceral, peripheral and central-to-peripheral adiposity together with comprehensive set of CM risk factors were obtained. Partial correlations and areas under the ROC curve (AUC) were estimated to compare each adiposity measure with CM risk parameters, separately for men and women, and in the overall sample.

RESULTS

DXA-derived indicators, other than percentage of total body fat, showed stronger correlations (rho -0.172 to 0.206, p < 0.001) with CM risk than anthropometric indicators, after controlling for age, diabetes and medication use. In both sexes, DXA-derived visceral adipose tissue measures (VAT, VAT/Total fat, visceral-to-subcutaneous fat) together with lipodystrophy indicators (Trunk/Legs fat and Android/Gynoid fat) were strongly and positively correlated (p < 0.001) with glycated hemoglobin (HbA1c), the triglyceride and glucose index (TyG), triglycerides (TG), the ratio TG/HDL-cholesterol (TG/HDL-C), and were inversely related to HDL-C levels (p < 0.001). Furthermore, in AUC analyses for both sexes, VAT/Total fat showed the highest predictive ability for abnormal HbA1c levels (AUC = 0.629), VAT for TyG (AUC = 0.626), both lipodystrophy indicators for TG (AUCs = 0.556), and Trunk/Legs fat for HDL-C (AUC = 0.556) and TG/HDL-C (AUC = 0.581).

CONCLUSIONS

DXA regional adiposity measures offer advantages beyond traditional anthropometric and DXA overall adiposity indicators for CM risk assessment in senior overweight/obese subjects with MetS. In particular, in both sexes, visceral adiposity better stratifies individuals at risk for glucose abnormalities, and indicators of lipodystrophy better predict markers of dyslipidemia.

Balanced high fat diet reduces cardiovascular risk in obese women although changes in adipose tissue, lipoproteins, and insulin resistance differ by race

BACKGROUND

We previously reported that consuming a balanced high fat diet (BHFD) wherein total saturated fat was reduced and total unsaturated fat increased by proportionately balancing the type of fat (1/3 saturated, 1/3 monounsaturated, 1/3 polyunsaturated) led to significant improvements in inflammatory burden, blood pressure, and vascular function in obese premenopausal European American (EA) and African American (AA) women.

OBJECTIVE

Here we compared changes in adipose tissue, lipoproteins, insulin resistance, and cardiovascular risk between EA and AA women.

METHODS

Dietary intakes, plasma fatty acids, lipids, apolipoproteins, lipoproteins, HOMA-IR and ASCVD risk was measured in 144 women who consumed BHFD for 16 weeks. Generalized linear modeling was performed while controlling for change in body weight.

RESULTS

EA women had greater reductions in visceral adipose tissue. Only EA women had significant reductions in fasting insulin levels (↓24.8%) and HOMA-IR (↓29%) scores. In EA women, the most significant improvements occurred in VLDL particle size (↑), apolipoprotein B levels (↑), serum TG (↓), number of plasma LDL particles (↓), and serum LDL-cholesterol (↓). In AA women, significant improvements occurred in HDL particle size (↑), number of large HDL particles (↑), and apolipoprotein AI levels (↑). Consequently, both groups had improved ASCVD risk scores (↓5.5%).

CONCLUSIONS

Consuming the balanced high fat diet led to significant reduction in cardiovascular risk factors in both groups. However, the pattern of response to BHFD differed with EA women responding more in components of the apolipoprotein B pathway versus AA women responding more in components of the apolipoprotein AI pathway.

Quantification of visceral adipose tissue in polycystic ovary syndrome: dual-energy X-ray absorptiometry versus magnetic resonance imaging

Background Polycystic ovary syndrome (PCOS) is associated with frequent overweight and abdominal obesity. Quantifying visceral adipose tissue (VAT) in PCOS patients can be a tool to assess metabolic risk and monitor effects of treatment. The latest dual-energy X-ray absorptiometry (DXA) technology can measure VAT and subcutaneous adipose tissue (SAT) in a clinical setting. Purpose To compare DXA-measurements of VAT and SAT with the gold standard MRI in women with PCOS. Material and Methods A cross-sectional study of 67 overweight women with PCOS was performed. Measurements of VAT and SAT were performed by DXA in a 5-cm thick transverse slice at the L4/L5 level and by MRI in a 1-cm thick transverse slice at the L3 level. Results Mean (SD) DXA-VAT was 81 (34) cm³, DXA-SAT was 498 (118) cm³, MRI-VAT was 117 (48) cm³, and MRI-SAT was 408 (122) cm³. MRI and DXA measures of VAT (r = 0.82, P < 0.001) and SAT (r = 0.92, P < 0.001) correlated closely, and DXA-VAT was stronger correlated with MRI-VAT than BMI (r = 0.62, P < 0.001) and waist circumference (r = 0.60, P < 0.001). DXA-VAT coefficient of variance was 6.7% and inter correlation coefficient was 0.98. Bland-Altman analyses showed DXA to slightly underestimate VAT and SAT measurements compared with MRI. Conclusion DXA and MRI measurements of VAT and SAT correlated closely despite different size of region of interest, and DXA-VAT was superior to waist circumference and BMI in estimating MRI-VAT. DXA showed high reproducibility making it is suitable for repeated measurements in the same individual over time.

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

We examined the reproducibility of dual-energy x-ray absorptiometry (DXA) visceral adipose tissue (VAT) estimates as well as the impact of pre-assessment diet. In a counterbalanced design, 41 adults received 6 DXA scans, while consuming standardized high- and low-carbohydrate (LC) diets. The impact of pre-assessment diet was examined via repeated-measures analysis of variance and reproducibility of VAT estimates was evaluated by technical error of measurement (TEM) and s.e. of a single determination (SESD). VAT area, mass and volume were acutely decreased by ~ 6.5% after the LC diet (P ≤ 0.001), but not the high-carbohydrate diet (P > 0.3). Differences persisted after an overnight fast. TEMs for VAT area, mass and volume were < 5 cm², ≤ 0.2 kg and < 25 cm³. SESDs for all VAT variables were ≤ 5.5%. In conclusion, DXA VAT estimates exhibit good reproducibility in controlled conditions, but may be impacted by pre-assessment diet.

Age-Related Changes in Fat Mass and Distribution in Men-the Cross-Sectional STRAMBO Study

Data on age-related differences in fat mass and distribution in men are scarce. We performed a cross-sectional analysis of age-related differences in fat distribution in men. In a cohort of 1133 men aged 20-87 yr, body composition was assessed using a Hologic Discovery A device. We assessed fat mass (FM) and FM indices adjusted for height. Interindividual variability was calculated as standard deviation, interquartile range, and difference between the 95th and 5th percentiles in 5-yr age groups. After adjustment for lifestyle factors, the FM and FM index of appendicular, gynoid, central, android, and subcutaneous abdominal compartments increased with age. Their variability did not vary with age. Visceral FM was 181% higher in men aged >80 yr compared to men aged 20-30 yr, and the variability increased with age. FM in the central, android, subcutaneous abdominal, and visceral compartments correlated with age significantly more strongly before the age of 70 than after this age. The relative differences between the elderly and younger men were greater for visceral FM than for subcutaneous (abdominal and appendicular) fat. The interindividual variability in visceral FM is higher in elderly men. The association between visceral FM and age is stronger before the age of 70.

Comparison of Associations of DXA and CT Visceral Adipose Tissue Measures With Insulin Resistance, Lipid Levels, and Inflammatory Markers

Visceral adipose tissue (VAT) measured by computed tomography (CT) is related to insulin resistance, lipids, and serum inflammatory markers. Our objective was to compare the strength of the associations of VAT measured using dual-energy X-ray absorptiometry (DXA-VAT) and CT (CT-VAT) with insulin resistance, serum lipids, and serum markers of inflammation. For 1117 men aged 65 and older enrolled in the Osteoporotic Fractures in Men Study, the cross-sectional associations of DXA-VAT and CT-VAT with homeostasis model assessment of insulin resistance (homa2ir), C-reactive protein, and high-density lipoprotein (HDL) cholesterol were estimated with regression models and compared using a Hausman test. Adjusted for age and body mass index, DXA-VAT was moderately associated with homa2ir (effect size 0.38, 95% confidence interval [CI]: 0.28-0.47) and modestly associated with HDL cholesterol (DXA effect size -0.29, 95% CI: -0.38 to -0.21). These associations were significantly greater than those for CT-VAT with homa2ir (0.30, 95% CI: 0.24-0.37; p value for effect size difference 0.03) and CT-VAT with HDL cholesterol (-0.22, 95% CI: -0.29 to -0.15; p value for difference 0.005). Neither DXA-VAT nor CT-VAT was associated with C-reactive protein after adjustment for age and body mass index (DXA-VAT effect size 0.14, 95% CI: -0.04 to 0.32; CT-VAT effect size 0.08, 95% CI: -0.08 to 0.25; p value for difference 0.35). DXA-VAT has similar or greater associations with insulin resistance and HDL cholesterol as does CT-VAT in older men, confirming the concurrent validity of DXA-VAT. Investigations of how well DXA measurements of VAT predict incident cardiovascular disease events are warranted.

Anthropometric discriminators of type 2 diabetes among White and Black American adults

BACKGROUND

The aim of the present study was to determine the best anthropometric discriminators of type 2 diabetes mellitus (T2DM) among White and Black males and females in a large US sample.

METHODS

We used Atherosclerosis Risk in Communities study baseline data (1987-89) from 15 242 participants (1827 with T2DM) aged 45-65 years. Anthropometric measures included a body shape index (ABSI), body adiposity index (BAI), body mass index, waist circumference (WC), waist:  height ratio (WHtR), and waist:  hip ratio (WHR). All anthropometric measures were standardized to Z-scores. Using logistic regression, odds ratios for T2DM were adjusted for age, physical activity, and family history of T2DM. The Akaike information criterion and receiver operating characteristic C-statistic were used to select the best-fit models.

RESULTS

Body mass index, WC, WHtR, and WHR were comparable discriminators of T2DM among White and Black males, and were superior to ABSI and BAI in predicting T2DM (P < 0.0001). Waist circumference, WHtR, and WHR were the best discriminators among White females, whereas WHR was the best discriminator among Black females. The ABSI was the poorest discriminator of T2DM for all race-gender groups except Black females. Anthropometric values distinguishing T2DM cases from non-cases were lower for Black than White adults.

CONCLUSIONS

Anthropometric measures that included WC, either alone or relative to height (WHtR) or hip circumference (WHR), were the strongest discriminators of T2DM across race-gender groups. Body mass index was a comparable discriminator to WC, WHtR, and WHR among males, but not females.

Best anthropometric discriminators of incident type 2 diabetes among white and black adults: A longitudinal ARIC study

Objective

To determine which anthropometric measures are the strongest discriminators of incident type 2 diabetes (T2DM) among White and Black males and females in a large U.S. cohort.

Methods

We used Atherosclerosis Risk in Communities study data from 12,121 participants aged 45–64 years without diabetes at baseline who were followed for over 11 years. Anthropometric measures included a body shape index (ABSI), body adiposity index (BAI), body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR), waist to height ratio (WHtR), and waist to hip to height ratio (WHHR). All anthropometric measures were repeated at each visit and converted to Z-scores. Hazard ratios and 95% confidence intervals adjusted for age were calculated using repeated measures Cox proportional hazard regression analysis. Akaike Information Criteria was used to select best-fit models. The magnitude of the hazard ratio effect sizes and the Harrell’s C-indexes were used to rank the highest associations and discriminators, respectively.

Results

There were 1,359 incident diabetes cases. Higher values of all anthropometric measures increased the risk for development of T2DM (p < 0.0001) except ABSI, which was not significant in White and Black males. Statistically significant hazard ratios ranged from 1.26–1.63 for males and 1.15–1.88 for females. In general, the largest hazard ratios were those that corresponded to the highest Harrell’s C-Index and lowest Akaike Information Criteria values. Among White and Black males and females, BMI, WC, WHR, and WHtR were comparable in discriminating cases from non-cases of T2DM. ABSI, BAI, and WHHR were inferior discriminators of incident T2DM across all race-gender groups.

Conclusions

BMI, the most commonly used anthropometric measure, and three anthropometric measures that included waist circumference (i.e., WC, WHR, WHtR) were the best anthropometric discriminators of incident T2DM across all race-gender groups in the ARIC cohort.

Visceral fat measured by DXA is associated with increased risk of non-spine fractures in nonobese elderly women: a population-based prospective cohort analysis from the São Paulo Ageing & Health (SPAH) Study

The present study investigates the relationship between visceral fat measured by dual-energy X-ray absorptiometry (DXA) and the incidence of non-spine fractures in community-dwelling elderly women. We demonstrated a potential negative effect of visceral fat on bone health in nonobese women.

INTRODUCTION

The protective effect of obesity on bone health has been questioned because visceral fat has been demonstrated to have a deleterious effect on bone. The aim of this study was to investigate the association of visceral fat measured by DXA with the incidence of non-spine fractures in community-dwelling elderly women.

METHODS

This longitudinal prospective population-based cohort study evaluated 433 community-dwelling women aged 65 years or older. A specific clinical questionnaire, including personal history of a fragility fracture in non-spine osteoporotic sites, was administered at baseline and after an average of 4.3 years. All incidences of fragility fractures during the study period were confirmed by affected-site radiography. Visceral adipose tissue (VAT) was measured in the android region of a whole-body DXA scan.

RESULTS

The mean age was 72.8 ± 4.7 years, and 28 incident non-spine osteoporotic fractures were identified after a mean follow-up time of 4.3 ± 0.8 years. According to the Lipschitz classification for nutritional status in the elderly, 38.6 % of women were nonobese (BMI ≤ 27 kg/m²) and 61.4 % were obese/overweight. Logistic regression models were used to estimate the relationship between VAT and non-spine fractures in elderly women. After adjusting for age, race, previous fractures, and BMD, VAT (mass, area, volume) had a significant association with the incidence of non-spine fractures only in nonobese elderly women (VAT mass: OR, 1.42 [95 % CI, 1.09-1.85; p = 0.010]; VAT area: OR, 1.19 [95 % CI, 1.05-1.36; p = 0.008]; VAT volume: OR, 1.40 [95 % CI, 1.09-1.80; p = 0.009]).

CONCLUSION

This study suggests a potential negative effect of visceral adiposity on bone health in nonobese women.

Physical activity, mental health, and weight gain in a longitudinal observational cohort of nonobese young adults

OBJECTIVE

To investigate the relationship among moderate-to-vigorous physical activity (MVPA), mental health symptoms, and weight gain in young adults.

METHODS

Fifty-nine healthy men and women (age 26.8 ± 4.7 years, body mass index [BMI] 22.4 ± 2.3 kg/m(2) ) were assessed at baseline and year 2. Weight, BMI, fat mass by dual-energy X-ray absorptiometry, anxiety and depression by the SCL-90, and MVPA by accelerometry were assessed. Sex-stratified linear regression models were used to examine associations between baseline anxiety/depression and body composition change, then repeated controlling for baseline MVPA.

RESULTS

Overall, weight, BMI, fat mass, and subcutaneous adiposity significantly increased at year 2 (P < 0.05). For women, a higher depression and anxiety score predicted increased weight, BMI, fat mass, and subcutaneous adiposity (P < 0.05). Controlling for MVPA attenuated these associations to nonsignificance. For men, MVPA did not alter the associations between anxiety and increased weight, BMI, fat mass, and subcutaneous adiposity (P < 0.05) or the associations between depression and decreased weight, BMI, fat mass, and subcutaneous adiposity (P < 0.05).

CONCLUSIONS

Anxiety and depression were related to body composition change for young adults. In women, MVPA attenuated these associations to nonsignificance. MVPA may buffer the adverse effects of depression and anxiety symptoms on young women's weight gain.

Genome-wide association studies suggest sex-specific loci associated with abdominal and visceral fat

BACKGROUND

To identify loci associated with abdominal fat and replicate prior findings, we performed genome-wide association (GWA) studies of abdominal fat traits: subcutaneous adipose tissue (SAT); visceral adipose tissue (VAT); total adipose tissue (TAT) and visceral to subcutaneous adipose tissue ratio (VSR).

SUBJECTS AND METHODS

Sex-combined and sex-stratified analyses were performed on each trait with (TRAIT-BMI) or without (TRAIT) adjustment for body mass index (BMI), and cohort-specific results were combined via a fixed effects meta-analysis. A total of 2513 subjects of European descent were available for the discovery phase. For replication, 2171 European Americans and 772 African Americans were available.

RESULTS

A total of 52 single-nucleotide polymorphisms (SNPs) encompassing 7 loci showed suggestive evidence of association (P<1.0 × 10(-6)) with abdominal fat in the sex-combined analyses. The strongest evidence was found on chromosome 7p14.3 between a SNP near BBS9 gene and VAT (rs12374818; P=1.10 × 10(-7)), an association that was replicated (P=0.02). For the BMI-adjusted trait, the strongest evidence of association was found between a SNP near CYCSP30 and VAT-BMI (rs10506943; P=2.42 × 10(-7)). Our sex-specific analyses identified one genome-wide significant (P<5.0 × 10(-8)) locus for SAT in women with 11 SNPs encompassing the MLLT10, DNAJC1 and EBLN1 genes on chromosome 10p12.31 (P=3.97 × 10(-8) to 1.13 × 10(-8)). The THNSL2 gene previously associated with VAT in women was also replicated (P=0.006). The six gene/loci showing the strongest evidence of association with VAT or VAT-BMI were interrogated for their functional links with obesity and inflammation using the Biograph knowledge-mining software. Genes showing the closest functional links with obesity and inflammation were ADCY8 and KCNK9, respectively.

CONCLUSIONS

Our results provide evidence for new loci influencing abdominal visceral (BBS9, ADCY8, KCNK9) and subcutaneous (MLLT10/DNAJC1/EBLN1) fat, and confirmed a locus (THNSL2) previously reported to be associated with abdominal fat in women.

Dual-energy X-ray absorptiometry body composition in patients with secondary osteoporosis

Due to the tight relationship between bone and soft tissues, there has been an increased interest in body composition assessment in patients with secondary osteoporosis as well as other pathological conditions. Dual-energy X-ray absorptiometry (DXA) is primarily devoted to the evaluation of bone mineral status, but continuous scientific advances of body composition software made DXA a rapid and easily available technique to assess body composition in terms of fat mass and lean mass. As a result, the International Society for Clinical Densitometry (ISCD) recently developed Official Positions regarding the use of this technique for body composition analysis. According to ISCD paper, indications are mainly limited to three conditions: HIV patients treated with antiretroviral agents associated with a risk of lipoatrophy; obese patients undergoing treatment for high weight loss; patients with sarcopenia or muscle weakness. Nevertheless, there are several other interesting clinical applications that were not included in the ISCD position paper, such as body composition assessment in patients undergoing organ transplantation, pulmonary disease as well as all those chronic condition that may lead to malnutrition. In conclusion, DXA body composition offers new diagnostic and research possibilities for a variety of diseases; due to its high reproducibility, DXA has also the potential to monitor body composition changes with pharmacological, nutritional or physic therapeutic interventions. ISCD addressed and recommended a list of clinical condition, but the crescent availability of DXA scans and software improvements may open the use of DXA to other indication in the next future. This article provides an overview of DXA body composition indications in the management of secondary osteoporosis and other clinical indications in adults.

Imaging methods for analyzing body composition in human obesity and cardiometabolic disease

Advances in the technological qualities of imaging modalities for assessing human body composition have been stimulated by accumulating evidence that individual components of body composition have significant influences on chronic disease onset, disease progression, treatment response, and health outcomes. Importantly, imaging modalities have provided a systematic method for differentiating phenotypes of body composition that diverge from what is considered normal, that is, having low bone mass (osteopenia/osteoporosis), low muscle mass (sarcopenia), high fat mass (obesity), or high fat with low muscle mass (sarcopenic obesity). Moreover, advances over the past three decades in the sensitivity and quality of imaging not just to discern the amount and distribution of adipose and lean tissue but also to differentiate layers or depots within tissues and cells is enhancing our understanding of distinct mechanistic, metabolic, and functional roles of body composition within human phenotypes. In this review, we focus on advances in imaging technologies that show great promise for future investigation of human body composition and how they are being used to address the pandemic of obesity, metabolic syndrome, and diabetes.

Visceral adipose tissue measured by DXA correlates with measurement by CT and is associated with cardiometabolic risk factors in children

BACKGROUND

Visceral adipose tissue (VAT) generally demonstrates a stronger relationship with cardiometabolic risk factors than total body fat or subcutaneous adipose tissue.

OBJECTIVES

The purpose of this study was to compare VAT estimated in children by total volume dual-energy X-ray absorptiometry (DXA) with a gold standard measurement, single slice (L4-L5) computed tomography (CT).

METHODS

A total of 329 (152 females, 177 males) children ages 6-18 years (mean age 12.3 ± 3.6) and with average body mass index percentile of 54.9% (3-99%) had their VAT estimated by both CT and DXA. Linear association between methods was measured using Pearson's correlation. Multiple linear regressions compared the associations between cardiometabolic risk factors and both CT-VAT and DXA-VAT, respectively.

RESULTS

In children, DXA-VAT was correlated significantly with CT-VAT, with a stronger relationship in overweight and obese children. Multiple regression analysis showed that both estimates of VAT were significantly associated with lipids and insulin sensitivity, measured by euglycaemic-hyperinsulinaemic clamp. Additionally, DXA-VAT was associated with diastolic blood pressure, homeostasis model of insulin resistance and fasting insulin, but CT-VAT was not.

CONCLUSION

In children, total volume DXA-VAT and single slice CT-VAT are significantly correlated and each demonstrates similar associations with cardiometabolic risk factors. This suggests that DXA is a useful and valid method for estimation of VAT in children.

Identification of sex-specific thresholds for accumulation of visceral adipose tissue in adults

OBJECTIVE

The purpose of this study was to measure the linearity of visceral adipose tissue (VAT) accumulation with measures of total body adiposity to determine whether a threshold exists and to explore the association with cardiometabolic risk factors in adults.

METHODS

Using a cross-sectional design, data were obtained from 723 adults (324 females) age 19-47 years. Body mass index ranged from 15 to 52 kg/m(2) . Segmented linear regression was used to identify sex-specific percent body fat thresholds at which VAT slope changes. Linear regression measured the association of VAT mass, total fat mass, and subcutaneous fat with cardiometabolic risk factors above and below each threshold.

RESULTS

Adiposity thresholds were identified at 23.4% body fat in males and 38.3% body fat in females beyond which the slope of VAT per unit of percent body fat increased to strongly positive. Males and females above these adiposity thresholds had significant dyslipidemia (P<0.001), increased insulin resistance (P<0.001), and higher fat mass across all depots.

CONCLUSIONS

From these cross-sectional data, the following were inferred: the accumulation of VAT mass is not linear with increasing adiposity; increases in visceral accumulation above threshold are associated with decreased insulin sensitivity and cardiovascular risk in males and females independent of total body fat.

DXA-measured visceral adipose tissue predicts impaired glucose tolerance and metabolic syndrome in obese Caucasian and African-American women

BACKGROUND/OBJECTIVES

New methods to measure visceral adipose tissue (VAT) by dual-energy X-ray absorptiometry (DXA) may help discern sex, race and phenotype differences in the role of VAT in cardiometabolic risk. This study was designed (1) to compare relationships of DXA-VAT, anthropometric and body composition variables with cardiometabolic risk factors in obese women; (2) to determine which variables most robustly predict impaired glucose tolerance (IGT) and metabolic syndrome (MetSx); and (3) to determine thresholds for DXA-VAT by race.

SUBJECTS/METHODS

VAT mass (g) and volume (cm(3)) were measured in 229 obese (body mass index (BMI), 30-49.9) women aged 21-69 years of European-American (EA=123) and African-American (AA=106) descent using the CoreScan algorithm on a Lunar iDXA scanner. Linear regression modeling and areas under the curve (AUC of ROC (receiver operating characteristic) curves) compared relationships with cardiometabolic risk. Bootstrapping with LASSO (least absolute shrinkage and selection operator) regression modeling determined thresholds and predictors of IGT and MetSx.

RESULTS

DXA-VAT explained more of the variance in triglycerides, blood pressure, glucose and homeostatic model assessment-insulin resistance (HOMA-IR) compared with anthropometric and other body composition variables. DXA-VAT also had the highest AUC for IGT (0.767) and MetSx (0.749). Including race as a variable and the interaction between VAT and race in modeling did not significantly change the results. Thresholds at which the probability of developing IGT or MetSx was⩾50% were determined separately for AA women (IGT: 2120 cm(3); MetSx: 1320 cm(3)) and EA women (IGT: 2550 cm(3); MetSx: 1713 cm(3)). The odds for IGT or MetSx were fourfold greater with each standard deviation increase in DXA-VAT.

CONCLUSIONS

DXA-VAT provides robust clinical information regarding cardiometabolic risk in AA and EA obese women and offers potential utility in the risk reduction interventions.

Obesity - should we revise indications for treatment with metformin?

Introduction

Treatment of obesity with life style modifications often fails; therefore pharmacological treatment has become a very popular approach. Metformin is one of the examined possibilities. The aim of this study was to verify indications for metformin use in obese women based on metabolic and anthropometric parameters assessed by dual-X-ray absorptiometry (DXA), to establish the degree of insulin resistance and its correlations.

Material and methods

Anthropometry, fat measurement by bioimpedance and metabolic profile, including lipids, and oral glucose tolerance test (OGTT) with insulin (0 and 120 min) were performed in 50 female patients diagnosed with simple obesity, aged 18-40 years. Homeostatic model assessment HOMA-R was calculated for insulin resistance, and area under the curve (AUC) for insulin response. Total, android and gynoid fat distribution, and their ratio (A/G), were measured by DXA.

Results

From 50 women who entered the study, 33 were classified as insulin resistant (IR subgroup) and 17 as non-insulin resistant (non-IR subgroup), according to their HOMA-R indices. IR women presented higher waist circumference and DXA A/G ratio. The IR subgroup demonstrated elevated fasting triglycerides and glucose (but in the normal range) and a higher insulin response in OGTT (4.1-fold vs 2.5-fold). From different insulin measurements HOMA index turned out to have the strongest correlations with the metabolic parameters triglycerides and glucose. We found significant positive correlations between android fat and insulin: waist circumference and HOMA-R, WHR and HOMA-R, android fat and HOMA-R, A/G ratio and insulin after OGTT, and A/G ratio and HOMA-R. We found a strong correlation between WHR and A/R ratio.

Conclusions

67% of premenopausal obese women were insulin resistant. Measures of DXA visceral fat determined by android fat percentage and android/gynoid ratio were the strongest determinants of insulin resistance. Waist-to-hip ratio might be a simple method for determining the indications for metformin treatment.

Commonality versus specificity among adiposity traits in normal-weight and moderately overweight adults

BACKGROUND

Many adiposity traits have been related to health complications and premature death. These adiposity traits are intercorrelated but their underlying structure has not been extensively investigated. We report on the degree of commonality and specificity among multiple adiposity traits in normal-weight and moderately overweight adult males and females (mean body mass index (BMI)=22.9 kg m(-2), s.d.=2.4).

METHODS

A total of 75 healthy participants were assessed for a panel of adiposity traits including leg, arm, trunk, total fat masses and visceral adipose tissue (VAT) derived from dual energy X-ray absorptiometry (DXA), hepatic and muscle lipids from proton magnetic resonance spectroscopy, fat cell volume from an abdominal subcutaneous adipose tissue biopsy (n=36) and conventional anthropometry (BMI and waist girth). Spearman's correlations were calculated and were subjected to factor analysis.

RESULTS

Arm, leg, trunk and total fat masses correlated positively (r=0.78-0.95) with each other. VAT correlated weakly with fat mass indicators (r=0.24-0.31). Intrahepatic lipids (IHL) correlated weakly with all fat mass traits (r=0.09-0.34), whereas correlations between DXA depots and intramyocellular lipids (IMCL) were inconsequential. The four DXA fat mass measures, VAT, IHL and IMCL depots segregated as four independent factors that accounted for 96% of the overall adiposity variance. BMI and waist girth were moderately correlated with the arm, leg, trunk and total fat and weakly with VAT, IHL and IMCL.

CONCLUSION

Adiposity traits share a substantial degree of commonality, but there is considerable specificity across the adiposity variance space. For instance, VAT, IHL and IMCL are typically poorly correlated with each other and are poorly to weakly associated with the other adiposity traits. The same is true for BMI and waist girth, commonly used anthropometric indicators of adiposity. These results do not support the view that it will be possible to identify adequate anthropometric indicators of visceral, hepatic and muscle lipid content in normal-weight and moderately overweight individuals.