The incidence of obesity in the United States and other developed countries is epidemic. Because the prevalence of comorbidities to obesity, such as type 2 diabetes, has also increased, it is clear there is a great need to monitor and treat obesity and its comorbidities. Body composition assessments vary in precision and in the target tissue of interest. The most common assessments are anthropometric and include weight, stature, abdominal circumference, and skinfold measurements. More complex methods include bioelectrical impedance, dual-energy X-ray absorptiometry, body density, and total body water estimates. There is no single universally recommended method for body composition assessment in the obese, but each modality has benefits and drawbacks. We present here the most common methods and provide guidelines by way of examples to assist the clinician/researcher in choosing methods appropriate to their situation.

Research Methods and Procedures:Contiguous 1-cmthick magnetic resonance (MR) images of the abdomen were collected from 820 African-American and white adults. Repeated-measures ANOVA was used to examine the effects of image location, sex, race, and age (Ն50 vs. Ͻ50 years) on adipose tissue areas. Maximum VAT area was identified for each subject from the raw data. Results: Compared to women, men had greater total VAT volume (p Ͻ 0.0001), and their maximum VAT area occurred higher in the abdomen (p Ͻ 0.0001). Among white men, maximim VAT area most frequently occurred 5 to 10 cm above L4-L5, whereas in the other groups, maximim VAT area most frequently occurred 1 to 4 cm above L4-L5 (p Ͻ 0.0001). African-American men had greater total VAT volume than African-American women (p Ͻ 0.01), but this sex difference was only significant using single images cranial to L4-L5 ϩ 2 cm. Age-related increases in VAT tended to be greatest 5 to 10 cm above L4-L5 in men and near L4-L5 in women. Discussion: A single MR image 5 to 10 cm above L4-L5 may allow more accurate conclusions than the L4-L5 image regarding group differences in visceral adiposity.

Objectives To assess the relationship between telomere length and adiposity, using dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI), in addition to conventional anthropometric proxies including body mass index (BMI) and cardiovascular disease risk factors. Methods A cross-sectional sample of 309 non-Hispanic white participants in the Fels Longitudinal Study aged 8 to 80 yr (52% female) was included. Average telomere length was measured by quantitative PCR. Results Telomere length was negatively correlated with age (r = −0.32, P < 0.0001) and had numerous significant correlations with established cardiovascular disease risk factors including waist circumference (r = −0.33), apolipoprotein B (r = −0.26), systolic blood pressure (r = −0.28), and fasting serum glucose (r = −0.15); all P < 0.0025. In back-ward selection linear regression models of telomere length, adiposity measures were consistently retained in the best models; BMI, waist circumference, hip circumference, total body fat, and visceral adipose tissue volume were all inversely associated with telomere length at the nominal P < 0.05 level or lower, independent of age, sex, systolic blood pressure, and fasting serum lipid, lipoprotein, and glucose concentrations. The negative association of BMI with telomere length was stronger among younger than older participants (P for interaction, 0.03). Conclusions Individuals with higher total and abdominal adiposity have lower telomere length, a marker of cellular senescence, suggesting obesity may hasten the aging process. Longitudinal studies are required to establish the causal association of early life adiposity with biological aging.

A single MR image located approximately at the L3 vertebra can accurately estimate total VAT volume in blacks and whites of both sexes.