[Show abstract][Hide abstract] ABSTRACT: Although widely applied as a phenotypic expression of adiposity in population and gene-search studies, body mass index (BMI) is also acknowledged to reflect muscularity even though relevant studies directly measuring skeletal muscle (SM) mass are lacking. The current study aimed to fill this important gap by applying advanced imaging methods to test the hypothesis that, after controlling first for adiposity, SM mass is also a significant determinant of BMI in a population-based sample.
Whole-body magnetic resonance imaging scans were completed in Coronary Artery Risk Development in Young Adults study subjects aged 33-45 years. Physical activity (PA) levels, alcohol intake and adequacy of food intake were assessed by standardized questionnaires.
The study included 58 African-American (AA) and 78 Caucasian (C) men; and 63 AA and 64 C women.
Whole-body adipose tissue (AT) and SM volumes.
AT was significantly predicted by not only BMI, but also PA and alcohol intake with total model R (2)'s of 0.68 (P<0.0001) for men and 0.89 (P<0.0001) for women. Men had more SM than AT at all levels of BMI whereas SM predominated in women at lower BMIs (C<26 kg/m(2); AA<28 kg/m(2)). In men, both AT and SM contributed a similar proportion of between-subject variation in BMI. In contrast, in women AT contributed approximately 30% more than SM to the variation in BMI. Developed allometric models indicated SM associations with AT, PA and race after adjusting for height. There was little association of age, lifestyle factors or race with BMI after controlling for both AT and SM.
Variation in muscularity provides a mechanistic basis for the previously observed nonspecificity of BMI as a phenotypic expression of adiposity. These quantitative observations have important implications when choosing adiposity measures in population and gene-search studies.
International journal of obesity (2005) 09/2009; 33(12):1363-73. · 5.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To identify differences in amount and distribution of fat and lean soft tissue in a cross-sectional study of subjects with and without type 2 diabetes and to determine whether any differences are affected by race/ethnicity or sex.
Overweight and obese (body mass index, BMI > or = 25 kg m(-2)) Black, White and Hispanic men (490) and women (825) with type 2 diabetes ((mean+/-s.d.) age 58.5+/-6.6; BMI 35.3+/-5.3) who had a baseline dual energy X-ray absorptiometry whole-body scan at the time of enrollment in the Look AHEAD clinical trial, and 242 healthy controls, 91 males and 151 females (age 55.3+/-8.6 years, BMI 30.7+/-4.2 kg m(-2)) who were participating in unrelated research and were scanned on the same densitometers.
Adjusted for gender, age, race, clinical site and body size, total fat mass was smaller in persons with type 2 diabetes than in controls (-1.4+/-0.3 (s.e.); 34.5 vs 35.8 kg, P<0.001) while trunk fat was larger (1.3+/-0.2 (s.e.); 19.9 vs 18.6 kg, P<0.001) and leg fat was smaller (-1.5+/-0.2 (s.e.); 10.7 vs 12.3 kg, P<0.001). The arms of subjects with type 2 diabetes did not have significantly less fat compared to controls. Adjusted trunk lean mass was larger in type 2 diabetes by 0.6 kg (28.4 vs 27.8 kg, P<0.001) while leg lean was smaller by 0.5 kg (18.1 vs 18.6 kg, P<0.001).
Type 2 diabetes is associated with less total fat, leg fat and leg lean mass and more truncal fat and lean mass than controls. The physiological processes producing these deviations in tissue distribution and their metabolic significance warrant further investigation.
International journal of obesity (2005) 06/2008; 32(5):780-7. · 5.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Visceral adipose tissue (VAT) is widely recognized as conveying the highest health risk in humans among the currently measurable adipose tissue compartments. A recent study indicated that the traditionally measured VAT area at L(4)-L(5) is not the VAT area with the highest correlation with total VAT volume. At present, it is unknown whether the area with the highest correlation is also the most strongly associated with obesity-related health risk.
The study aim was to establish which VAT slice area(s) are most strongly associated with obesity-related health risk indicators.
The subjects were a convenience sample of healthy adults who completed whole-body magnetic resonance imaging (MRI) scans. The correlations, with appropriate adjustments, were examined between individual MRI slice VAT areas and fasting serum/plasma triglycerides (TG), high-density lipoprotein cholesterol (HDL), glucose, insulin and blood pressure.
The sample consisted of 283 healthy men (age (mean+/-s.d.) 41.9+/-15.8 years; BMI, 26.0+/-3.2 kg/m(2); VAT, 2.7+/-1.8 L) and 411 women (age, 48.1+/-18.7 years; BMI 27.0+/-5.4 kg/m(2); VAT, 1.7+/-1.2 L). After adjusting for age, race, menopause status, scan position and specific blood analysis laboratory, VAT area at L(4)-L(5) had lower correlations with most metabolic risk factors including serum/plasma TG, HDL, glucose, insulin and blood pressure than VAT volume in both men and women. The VAT areas 10 and 15 cm above L(4)-L(5) in men had higher or equal correlations with health risk measures than VAT volume. In women, the VAT area 5 cm above or below L(4)-L(5) and total VAT volume had similar correlations with health risk measures.
An appropriately selected single slice VAT area is an equally reliable phenotypic marker of obesity-related health risk as total VAT volume. However, in both men and women the VAT slice area at the traditional L(4)-L(5) level is not the best marker of obesity-related health risk.
International Journal of Obesity 06/2007; 31(5):763-9. · 5.22 Impact Factor