Latent common genetic components of obesity traits.

BACKGROUND: Obesity is rapidly becoming a global epidemic. Unlike many complex human diseases, obesity is defined not just by a single trait or phenotype, but jointly by measures of anthropometry and metabolic status. METHODS: We applied maximum likelihood factor analysis to identify common latent factors underlying observed covariance in multiple obesity-related measures. Both the genetic components and the mode of inheritance of the common factors were evaluated. A total of 1775 participants from 590 families for whom measures on obesity-related traits were available were included in this study. RESULTS: The average age of participants was 37 years, 39% of the participants were obese (body mass index >or= 30.0 kg/m(2)) and 26% were overweight (body mass index 25.0-29.9 kg/m(2)). Two latent common factors jointly accounting for over 99% of the correlations among obesity-related traits were identified. Complex segregation analysis of the age- and sex-adjusted latent factors provide evidence for a Mendelian mode of inheritance of major genetic effect with heritability estimates of 40.4 and 47.5% for the first and second factors, respectively. CONCLUSIONS: These findings provide a support for multivariate-based approach for investigating pleiotropic effects on obesity-related traits, which can be applied in both genetic linkage and association mapping.

Comparability of resting energy expenditure in Nigerians and U.S. blacks.

OBJECTIVE: To determine the influence of environmental factors on resting energy expenditure (REE) and its relationship to adiposity in two populations of West African origin, Nigerians and U.S. blacks. RESEARCH METHODS AND PROCEDURES: REE and body composition were measured in a cross-sectional sample of 89 Nigerian adults (39 women and 50 men), and 181 U.S. black adults (117 women and 65 men). Both groups represent randomly selected population samples. REE was measured by indirect calorimetry after an overnight fast in both sites using the same instrument. Body composition was estimated using bioelectrical impedance analysis (BIA) in 72 Nigerians and 156 U.S. participants. Multivariate regression analysis was used to determine the significant predictors of REE. The analyses were repeated in a set of 17 Nigerians and 28 U.S. blacks in whom body composition was measured using deuterium dilution. RESULTS: U.S. black adults were significantly heavier and had both more fat-free mass (FFM) and body fat than Nigerians. FFM was the only significant determinant of REE in both population groups, whether body composition was measured using BIA or deuterium dilution. The relationship between REE and body composition did not differ by site. There was no relationship between REE and adiposity. DISCUSSION: Differences in current environmental settings did not impact REE. The differences observed in mean levels of body fat between Nigerians and U.S. blacks were not the result of differences in REE adjusted for body composition.