The use of anthropometric and dual-energy X-ray absorptiometry (DXA) measures to estimate total abdominal and abdominal visceral fat in men and women

Adipose tissue quantification by imaging methods: a proposed classification

Recent advances in imaging techniques and understanding of differences in the molecular biology of adipose tissue has rendered classical anatomy obsolete, requiring a new classification of the topography of adipose tissue. Adipose tissue is one of the largest body compartments, yet a classification that defines specific adipose tissue depots based on their anatomic location and related functions is lacking. The absence of an accepted taxonomy poses problems for investigators studying adipose tissue topography and its functional correlates. The aim of this review was to critically examine the literature on imaging of whole body and regional adipose tissue and to create the first systematic classification of adipose tissue topography. Adipose tissue terminology was examined in over 100 original publications. Our analysis revealed inconsistencies in the use of specific definitions, especially for the compartment termed "visceral" adipose tissue. This analysis leads us to propose an updated classification of total body and regional adipose tissue, providing a well-defined basis for correlating imaging studies of specific adipose tissue depots with molecular processes.

Association of swim distance and age with body composition in adult female swimmers

PURPOSE

The purpose of this investigation was to examine the relationship between average weekly swimming distance and age with body composition in adult female endurance swimmers.

METHODS

Thirty-five women, aged 21-73 yr, volunteered to participate. Weekly swimming distance was determined from a self-reported exercise log. Body composition was estimated by dual-energy x-ray absorptiometry (DXA), waist circumference, abdominal sagittal diameter, and skinfold thickness measures. Associations between swimming distance and age with body composition were examined using regression analysis.

RESULTS

Swimming distance had shared variances as follows: 23% with percent body fat, 26% with waist circumference, 20% with abdominal sagittal diameter, and 20%, 24%, and 22% with subscapular, suprailiac, and triceps skinfolds, respectively. Abdominal sagittal diameter was the only adiposity measure demonstrating a stronger relationship with age (R2 = 0.29, P = 0.00) than with swimming distance (R2 = 0.20, P = 0.03). Bone mineral content was linearly related to swimming distance and age having a negative association with age (r2 = 0.18, P = 0.01) and a positive one with swimming distance (r2 = 0.12, P = 0.05). In addition, there was a negative linear association observed between swimmer age and bone mineral density (r2 = 0.12, P = 0.05).

CONCLUSION

In these female adults, endurance swimming was mildly associated with body adiposity. Age was not associated with body fat mass independently from swimming activity except with that measure reflecting abdominal visceral fat deposits. These data suggest that greater fat mass in female swimmers is more strongly related to lower levels of exercise than to age but that there is an additional influence of age on fat accumulation in the intra-abdominal area of the body.

The prediction of visceral fat by dual-energy X-ray absorptiometry in the elderly: a comparison with computed tomography and anthropometry

INTRODUCTION

Effective methods for assessing visceral fat are important to investigate the role of visceral fat for the increased health risks in obesity. Techniques for direct measurement of soft tissue composition such as CT or MRI are expensive, time-consuming or require a relatively high radiation dose. Simple anthropometric methods, such as waist-to-hip ratio, waist circumference or sagittal diameter are widely used. However, these methods cannot differentiate between visceral and subcutaneous fat and are less accurate. The aim of the present study is to investigate whether the dual-energy X-ray absorptiometry (DXA) method, possibly combined with anthropometry, offers a good alternative to CT for the prediction of visceral fat in the elderly.

METHODS

Subjects were participants in the Health ABC-study, a cohort study of black and white men and women aged 70-79, investigating the effect of weight-related health conditions on disablement. Total body fat and trunk fat were measured by DXA using a Hologic QDR 1500. A 10 mm CT scan at the L4-L5 level was acquired to measure visceral fat and total abdominal fat. Weight, height, sagittal diameter and waist circumference were measured using standard methods. Fat in a manually defined DXA subregion (4 cm slice at the top of iliac crest) at the abdomen was calculated in a sub-group of participants (n=150; 50% male; 45.3% Afro-American/54.7% Caucasian, age 70-79 y). This subregion, the standard trunk region and total fat were used as indicators of visceral fat.

RESULTS

Total abdominal fat by DXA (subregion) was strongly correlated with total abdominal fat by CT (r ranging from 0.87 in white men to 0.98 in black women). The DXA subregion underestimated total abdominal fat by 10% compared to the CT slice. The underestimation by DXA was seen especially in people with less abdominal fat. The association of visceral fat by CT with the DXA subregion (r=0.66, 0.78, 0.79 and 0.65 for white and black men and women, respectively) was comparable with the association of the CT measure with the sagittal diameter (r=0.74, 0.70, 0.84 and 0.68). Combining DXA measurements with anthropometry gave only limited improvement for the prediction of visceral fat by CT compared to univariate models (maximal increase of r(2) 4%).

CONCLUSION

DXA is a good alternative to CT for predicting total abdominal fat in an elderly population. For the prediction of visceral fat the sagittal diameter, which has a practical advantage compared to DXA, is just as effective.

Are dual-energy X-ray absorptiometry regional estimates associated with visceral adipose tissue mass?

OBJECTIVE

Recent studies support the possibility of estimating abdominal fat using a region of interest (ROI) selected by conventional whole body dual-energy X-ray absorptiometry (DXA). This is an important observation as DXA ROI estimates have some advantages over waist circumference or computed tomography/magnetic resonance imaging (MRI) as a means of assessing visceral adipose tissue (VAT) and adipose tissue distribution. The aim of this study was to evaluate the usefulness of DXA abdominal ROI estimates in assessing VAT among non-obese men.

DESIGN

Observational, cross-sectional study comparing correlations between MRI-measured total VAT and surrogate measures including DXA ROIs. A stepwise multiple regression model was applied to derive a predictive equation with total VAT mass.

SUBJECTS

Ninety non-obese healthy men between the ages of 18 and 44 y with BMI<30 kg/m(2).

MEASUREMENTS

Abdominal adipose tissue and total VAT were measured by whole body MRI; VAT area by single-slice MRI at the L4-5 level; specific DXA ROIs for abdominal regional fat defined as ROI A (L2-4), B (L2-upper iliac), C (lower costal-upper iliac), and D (ROI C excluding spine); and simple anthropometric measures.

RESULTS

Correlations between total VAT and ROIs A (r=0.85) and B (r=0.84) were not significantly different from that of VAT area at L4-5 (r=0.87), but significantly higher (P <0.01) than that of waist circumference (r=0.77). The highest correlations with total abdominal adipose tissue were for DXA ROIs and conventional DXA trunk fat (r=0.95-0.97). A stepwise multiple regression analysis revealed that 86% of the variance in total VAT was predicted by VAT area at L4-5, ROI A, and waist-hip ratio.

CONCLUSIONS

DXA ROIs (L2-4, L2-upper iliac) were associated with total VAT as well as MRI-derived VAT area at L4-5 in non-obese men. DXA ROI fat distribution estimates may be useful in the early detection of men with abdominal/visceral obesity.

Methods of assessing body shape and composition in HIV-associated lipodystrophy

Although HIV-associated lipodystrophy can be diagnosed just from clinical examination, criteria for diagnosis and judgement of severity are not clearly defined. Clinical assessment can be systematized with questionnaires for patients and physicians. Computed tomography, nuclear magnetic imaging and dual-energy X-ray absorptiometry are objective reference methods but are expensive for routine follow-up and diagnosis. Therefore, anthropometry and other non-invasive bedside methods deserve further validation studies.

Usefulness of lumbar AP spine DXA for measuring the percentage of perilumbar regional fat and predicting visceral fat in obese postmenopausal women

We investigated whether measurement of the perilumbar regional fat amount by lumbar spine DXA is as good a predictor of visceral fat in obese postmenopausal women. Twenty-two obese (BMI 30-383 kg/m(2)) and 18 nonobese (BMI 20.1-24.7 kg/m(2)) postmenopausal women with similar age were recruited. Lumbar AP spine DXA for measuring the percentage of perilumbar regional fat and CT scanning for estimation of the abdominal visceral fat areas were performed. In obese subjects, visceral fat areas as measured by CT were significantly correlated with BMI, waist circumference, WHR, and DXA-measured perilumbar regional fat percentage. In nonobese subjects, visceral fat areas measured with CT were correlated with BMI, waist circumference, WHR, and DXA-measured perilumbar regional fat percentage. The results of multiple regression analysis were that the perilumbar regional fat percent by DXA was the best predictor of visceral fat amount in obese postmenopausal women (R(2) = 0.750) and BMI predicted visceral fat amount in nonobese postmenopausal women (R(2) = 0.343). This study suggests that lumbar regional fat percentage, as measured by DXA, is a better predictor of abdominal visceral fat amount than waist circumference, WHR, or BMI in obese postmenopausal women.

Conjugated linoleic acid (CLA) reduced abdominal adipose tissue in obese middle-aged men with signs of the metabolic syndrome: a randomised controlled trial

BACKGROUND

Abdominal obesity is strongly related to metabolic disorders. Recent research suggests that dietary conjugated linoleic acid (CLA) reduces body fat and may improve metabolic variables in animals. The metabolic effects of CLA in abdominally obese humans have not yet been tested.

OBJECTIVE

To investigate the short-term effect of CLA on abdominal fat and cardiovascular risk factors in middle-aged men with metabolic disorders.

METHODS

Twenty-five abdominally obese men (waist-to-hip ratio (WHR), 1.05+/-0.05; body mass index (BMI), 32+/-2.7 kg/m(2) (mean+/-s.d.)) who were between 39 and 64-y-old participated in a double-blind randomised controlled trial for 4 weeks. Fourteen men received 4.2 g CLA/day and 10 men received a placebo. The main endpoints were differences between the two groups in sagittal abdominal diameter (SAD), serum cholesterol, low-density lipoprotein, high-density lipoprotein, triglycerides, free fatty acids, glucose and insulin.

RESULTS

At baseline, there were no significant differences between groups in anthropometric or metabolic variables. After 4 weeks there was a significant decrease in SAD (cm) in the CLA group compared to placebo (P=0.04, 95% CI; -1.12, -0.02). Other measurements of anthropometry or metabolism showed no significant differences between the groups.

CONCLUSIONS

These results indicate that CLA supplementation for 4 weeks in obese men with the metabolic syndrome may decrease abdominal fat, without concomitant effects on overall obesity or other cardiovascular risk factors. Because of the limited sample size, the effects of CLA in abdominal obesity need to be further investigated in larger trials with longer duration.

Metabolic age modelling: the lesson from centenarians

Evolutionary theories of ageing, and data emerging from cellular and molecular biology of ageing, suggested that animals and humans capable of reaching an age close to the extreme limit of the life span should be equipped with a very efficient network of anti-ageing mechanisms. Indeed several evidences have demonstrated that starting from young to very old subjects, ageing is associated with a progressive remodelling. Thus, a new paradigm, the remodelling theory of age, was proposed. This theory, focusing on the human immune system, suggested that immunosenescence is the net result of the continuous adaptation of the body to the deteriorative changes occurring over time. According to this hypothesis, body resources are continuously optimized, and immunosenescence must be considered a very dynamic process including both loss and gain. Whether the metabolic pathways and the endocrine functions are also part of the age remodelling is not investigated. The aim of this review is to focus on the age-related changes in metabolic pathways and endocrine functions and to demonstrate that healthy centenarians (HC) represent the best living example of successful age-remodelling in whom the age remodelling has occurred without problems. In order to design the clinical picture of such successful ageing, anthropometric, endocrine and metabolic characteristics of healthy centenarians (HC), compared with aged subject, have been outlined.

Critical value for the index of body fat distribution based on waist and hip circumferences and stature in obese girls

OBJECTIVE

To determine the critical value for the standard deviation score (SDS) of waist-hip ratio (WHR)/height (Ht), as an age-adjusted measure of body fat distribution, in relation to occurrence of biochemical complications in obese girls.

DESIGN

Cross-sectional, clinical study. The (WHR/Ht)-SDS was calculated as described previously. Obese girls were classified into two groups according to the occurrence of abnormal values in either serum triglyceride, alanine aminotransferase or insulin level. The criteria for obesity were subjected to the receiver operating characteristic (ROC) analysis.

SUBJECTS

One-hundred and twenty-four outpatient Japanese obese girls, ranging in age from 9 to 15 y.

MEASUREMENTS

Height, body weight, waist girth and hip girth as anthropometric measures. Percentage overweight, waist girth, WHR and (WHR/Ht)-SDS as criteria for obesity. Clinical laboratory analysis for fasting blood samples of obese children.

RESULTS

Fifty-nine girls were classified into the no complication group, and 65 girls into the complication group. Those with complications were older, more obese, and their waist girth and WHR were larger, than the girls without complications. The (WHR/Ht)-SDS was >2-fold higher and lipoprotein profile was more atherogenic in the complication group than in the no complication group. Among the four criteria of obesity, (WHR/Ht)-SDS gave the ROC curve skewed furthest into the top left corner of the diagram. Both sensitivity and specificity for (WHR/Ht)-SDS were >80% at the critical value of 2.00. The sensitivity for waist girth was as high as that for specificity for the rest of the criteria were <80%.

CONCLUSION

Only (WHR/Ht)-SDS showed high enough sensitivity and specificity to predict metabolic derangement in the present obese girls. (WHR/Ht)-SDS can serve as the diagnostic criterion that classifies obesity in Japanese adolescent girls into two types.