BACKGROUND: Understanding the factors that contribute to physical inactivity in children is important because sedentary behavior strongly relates to metabolic disorders such as obesity and diabetes. OBJECTIVE: We aimed to quantify the genetic and environmental influences on physical activity energy expenditure (PAEE) in 100 sex-concordant dizygotic (n = 38) and monozygotic (n = 62) twin pairs aged 4-10 y. DESIGN: Resting metabolic rate (RMR) was assessed by using respiratory gas exchange, total energy expenditure (TEE) by using doubly labeled water, and body composition by using dual-energy X-ray absorptiometry. Structural equation modeling was used to partition the phenotypic variance into additive genetic (a2) and common (c2) and unshared (e2) environmental components. RESULTS: Because PAEE [TEE - (RMR + 0.1 x TEE)] depends on body weight, which is highly heritable, we tested several models: 1) after adjustment for age, sex, ethnicity, study date, season, and weight, a2 explained none of the phenotypic variance in PAEE (95% CI: 0%, 38%), whereas c2 and e2 accounted for 69% (33%, 77%; P = 0.001) and 31% (23%, 39%; P < 0.001) of the variance, respectively; 2) after adjustment for the cofactors in model 1, a2 explained 19% of the phenotypic variance in TEE (0%, 60%; P = 0.13), whereas c2 and e2 accounted for 59% (16%, 79%; P = 0.007) and 23% (17%, 31%; P < 0.0001) of the variance, respectively; 3) in models adjusted as above (excluding weight), a2 explained no variance in physical activity level (TEE/RMR) (0%, 32%; P = 0.50), whereas c2 and e2 explained 65% (34%, 60%; P = 0.001) and 35% (28%, 45%; P < 0.0001) of the variance, respectively. CONCLUSIONS: Our data suggest that the familial resemblance in physical activity in these children is explained predominantly by shared environmental factors and not by genetic variability.
BACKGROUND: Understanding the factors that contribute to physical inactivity in children is important because sedentary behavior strongly relates to metabolic disorders such as obesity and diabetes. OBJECTIVE: We aimed to quantify the genetic and environmental influences on physical activity energy expenditure (PAEE) in 100 sex-concordant dizygotic (n = 38) and monozygotic (n = 62) twin pairs aged 4-10 y. DESIGN: Resting metabolic rate (RMR) was assessed by using respiratory gas exchange, total energy expenditure (TEE) by using doubly labeled water, and body composition by using dual-energy X-ray absorptiometry. Structural equation modeling was used to partition the phenotypic variance into additive genetic (a2) and common (c2) and unshared (e2) environmental components. RESULTS: Because PAEE [TEE - (RMR + 0.1 x TEE)] depends on body weight, which is highly heritable, we tested several models: 1) after adjustment for age, sex, ethnicity, study date, season, and weight, a2 explained none of the phenotypic variance in PAEE (95% CI: 0%, 38%), whereas c2 and e2 accounted for 69% (33%, 77%; P = 0.001) and 31% (23%, 39%; P < 0.001) of the variance, respectively; 2) after adjustment for the cofactors in model 1, a2 explained 19% of the phenotypic variance in TEE (0%, 60%; P = 0.13), whereas c2 and e2 accounted for 59% (16%, 79%; P = 0.007) and 23% (17%, 31%; P < 0.0001) of the variance, respectively; 3) in models adjusted as above (excluding weight), a2 explained no variance in physical activity level (TEE/RMR) (0%, 32%; P = 0.50), whereas c2 and e2 explained 65% (34%, 60%; P = 0.001) and 35% (28%, 45%; P < 0.0001) of the variance, respectively. CONCLUSIONS: Our data suggest that the familial resemblance in physical activity in these children is explained predominantly by shared environmental factors and not by genetic variability.
Authors: Charlotte Huppertz; Meike Bartels; Catherina E M Van Beijsterveldt; Dorret I Boomsma; James J Hudziak; Eco J C De Geus Journal: Med Sci Sports Exerc Date: 2012-10 Impact factor: 5.411
Authors: Lisa G Rosas; Sylvia Guendelman; Kim Harley; Lia C H Fernald; Lynnette Neufeld; Fabiola Mejia; Brenda Eskenazi Journal: J Immigr Minor Health Date: 2011-02
Authors: P W Franks; K A Jablonski; L Delahanty; R L Hanson; S E Kahn; D Altshuler; W C Knowler; J C Florez Journal: Diabetologia Date: 2007-09-27 Impact factor: 10.122
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