1. Objectifs

Intentions :
Evaluate « genetic and [family] environmental contributions to body size from birth to 5 years in a population-based twin cohort [...] » (p. 479)

Questions/Hypothèses :
Quelle est la part des gènes dans le phénomène de l’obésité chez les jeunes?

2. Méthode

Échantillon/Matériau :
« [...] 177 complete twin pairs. » (p. 479) of the « [...] Quebec Newborn Twin Study (QNTS; Pérusse, 1995) [...] » (p. 480)

Type de traitement des données :
Analyse statistique

3. Résumé

« This study sheds light on the respective contributions of genes and family environnemental factors on body size measures in the first half of childhood. » (pp. 482-483) « Heritability of weight was moderate at birth while common environmental factors accounted for almost half of the variance. Influence of family environment disappeared by 5 months and genetic effects were high (approximately 90%) for both sexes at 5 months and 5 years. Adjustment of weight for height yielded similar results as for weight alone. Slight but significant sex-limitation of genetic effects was observed at 5 months. Overall, genetic factors accounted for 40% of birthweight variance, with intrauterine environment influences explaining almost half. However, genetic factors accounted for most of the variance in weight. These results do not imply a lack of environmental effects on body weight, but rather a lack of: (1) environmental effects that are independent from genetic liability, and/or (2) a lack of significant environmental variation in the population (e.g., uniform nutritional habits) that leaves genetic differences between children to generate most of the variance in weight. » (p. 479)