Distribution and heritability of BMI in Finnish adolescents aged 16 y and 17 y: A study of 4884 twins and 2509 singletons

Abstract

OBJECTIVE: 1) To estimate the heritability of body mass index (BMI) in twins aged 16 y and 17 y, with a special emphasis on gender-speci®c genetic effects and 2) to compare heights, weights, BMIs, and prevalences of`overweight' (BMI ! ! 25 kgam 2 ) in these twins and in singletons aged 16.5 y. DESIGN: Cross-sectional and longitudinal epidemiological questionnaire study of twins at ages 16 y and 17 y, and cross-sectional study of singletons at age 16.5 y. MEASUREMENTS: BMI (kgam 2 ) was calculated from self-reported heights (m) and weights (kg). SUBJECTS: 4884 twins (2299 boys, 2585 girls) at baseline (age 16 y), 4401 twins (2002 boys, 2399 girls) at age 17 y, and 2509 singletons (1147 boys, 1362 girls) at age 16.5 y. Both twin and singleton samples are nationally representative. RESULTS: At the ages of 16 y and 17 y, genetic effects accounted for over 80% of the interindividual variation of BMI. The correlations for male ± female pairs were smaller than for either male-male or female ± female dizygotic pairs. The singletons, especially the boys, had a higher BMI than the twins. Nine percent of singleton boys, but only 4 ± 6% of twin boys and twin and singleton girls were`overweight' (BMI ! ! 25 kgam 2 ). CONCLUSIONS: Among adolescents, genetic factors play a signi®cant role in the causes of variation in BMI. The genetic modelling suggested that the sets of genes explaining the variation of BMI may differ in males and females. At this age, the twin boys, but not girls, seem to be leaner than singletons. Further follow-up will indicate whether these small differences disappear, and if not, what implications it might have to the generalizability of twin studies.

Body Size of Twins Compared with Siblings and the General Population: From Birth to Late Adolescence

“…A study in Finnish adolescent twins reported that 17-year-old twin boys had reached the same height as singletons but still had a lower BMI. 13 The same tendency, although not reaching significance, was seen in girls. They suggested that the catch-up growth from the lighter birth weight may not (yet) be completed in twin boys.…”

“…10 Several studies have shown that the differences in body size between twins and singletons at birth disappeared during childhood, but in a few studies differences remained until adulthood. [11][12][13][14][15] The Louisville Twin Study concluded that the effects of prenatal growth suppression on weight and height appeared to be fully dissipated by age 8, 11 and a Finnish study among 17-year-old twins reported that twins were as tall as singletons, but that boy twins were still leaner. 13 We found in a previous study that at the age of 5 years, female twins were as tall as singleton children, whereas male twins were still somewhat shorter than children in the general population.…”

The genetic and environmental influences on childhood obesity: a systematic review of twin and adoption studies

“…These results are based on the meta-analysis of the nine existing twin studies. [13][14][15][16][17][18][19][20][21] Background information of these cohorts is presented in Appendix Table A1 and the estimates of variance components with 95% CI for each study in Appendix Table A2.…”

“…In the case when studies reporting correlations in BMI have been presented several times in different papers, only one paper was included. On the basis of these criteria, we found nine twin studies [13][14][15][16][17][18][19][20][21] and five adoption studies; [22][23][24][25][26] however, no family studies reporting heritability estimates of childhood obesity were found. In addition, we found three twin studies that had pooled information on children at different ages.…”

Low body weight and its association with bone health and pubertal maturation in Chinese girls

“…These results suggest protein and energy intakes and school physical education activity might also contribute to BMI, though that BMI is mainly genetically determined (Pietilainen et al, 1999). Socioeconomic area was another environmental factor associated with BMI (Table 1), probably reflecting the uneven rate of development in different areas of China in recent years.…”