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Silventoinen, Karri,Jelenkovic, Aline,Sund, Reijo,Yokoyama, Yoshie,Hur, Yoon-Mi,Cozen, Wendy,Hwang, Amie E,Mack, Thomas M,Honda, Chika,Inui, Fujio,Iwatani, Yoshinori,Watanabe, Mikio,Tomizawa, Rie,Piet American Society for Clinical Nutrition 2017 The American journal of clinical nutrition Vol.106 No.2
<P><B>Background:</B> Genes and the environment contribute to variation in adult body mass index [BMI (in kg/m<SUP>2</SUP>)], but factors modifying these variance components are poorly understood.</P><P><B>Objective:</B> We analyzed genetic and environmental variation in BMI between men and women from young adulthood to old age from the 1940s to the 2000s and between cultural-geographic regions representing high (North America and Australia), moderate (Europe), and low (East Asia) prevalence of obesity.</P><P><B>Design:</B> We used genetic structural equation modeling to analyze BMI in twins ≥20 y of age from 40 cohorts representing 20 countries (140,379 complete twin pairs).</P><P><B>Results:</B> The heritability of BMI decreased from 0.77 (95% CI: 0.77, 0.78) and 0.75 (95% CI: 0.74, 0.75) in men and women 20–29 y of age to 0.57 (95% CI: 0.54, 0.60) and 0.59 (95% CI: 0.53, 0.65) in men 70–79 y of age and women 80 y of age, respectively. The relative influence of unique environmental factors correspondingly increased. Differences in the sets of genes affecting BMI in men and women increased from 20–29 to 60–69 y of age. Mean BMI and variances in BMI increased from the 1940s to the 2000s and were greatest in North America and Australia, followed by Europe and East Asia. However, heritability estimates were largely similar over measurement years and between regions. There was no evidence of environmental factors shared by co-twins affecting BMI.</P><P><B>Conclusions:</B> The heritability of BMI decreased and differences in the sets of genes affecting BMI in men and women increased from young adulthood to old age. The heritability of BMI was largely similar between cultural-geographic regions and measurement years, despite large differences in mean BMI and variances in BMI. Our results show a strong influence of genetic factors on BMI, especially in early adulthood, regardless of the obesity level in the population.</P>
Silventoinen, Karri,Jelenkovic, Aline,Sund, Reijo,Hur, Yoon-Mi,Yokoyama, Yoshie,Honda, Chika,Hjelmborg, Jacob vB,Moller, Soren,Ooki, Syuichi,Aaltonen, Sari,Ji, Fuling,Ning, Feng,Pang, Zengchang,Rebato American Society for Clinical Nutrition 2016 The American journal of clinical nutrition Vol.104 No.2
<P>Background: Both genetic and environmental factors are known to affect body mass index (BMI), but detailed understanding of how their effects differ during childhood and adolescence is lacking. Objectives: We analyzed the genetic and environmental contributions to BMI variation from infancy to early adulthood and the ways they differ by sex and geographic regions representing high (North America and Australia), moderate (Europe), and low levels (East Asia) of obesogenic environments. Design: Data were available for 87,782 complete twin pairs from 0.5 to 19.5 y of age from 45 cohorts. Analyses were based on 383,092 BMI measurements. Variation in BMI was decomposed into genetic and environmental components through genetic structural equation modeling. Results: The variance of BMI increased from 5 y of age along with increasing mean BMI. The proportion of BMI variation explained by additive genetic factors was lowest at 4 y of age in boys (a(2) = 0.42) and girls (a(2) = 0.41) and then generally increased to 0.75 in both sexes at 19 y of age. This was because of a stronger influence of environmental factors shared by co-twins in midchildhood. After 15 y of age, the effect of shared environment was not observed. The sex-specific expression of genetic factors was seen in infancy but was most prominent at 13 y of age and older. The variance of BMI was highest in North America and Australia and lowest in East Asia, but the relative proportion of genetic variation to total variation remained roughly similar across different regions. Conclusions: Environmental factors shared by co-twins affect BMI in childhood, but little evidence for their contribution was found in late adolescence. Our results suggest that genetic factors play a major role in the variation of BMI in adolescence among populations of different ethnicities exposed to different environmental factors related to obesity.</P>