An Adoption Study of Human Obesity

Abstract

We examined the contributions of genetic factors and the family environment to human fatness in a sample of 540 adult Danish adoptees who were selected from a population of 3580 and divided into four weight classes: thin, median weight, overweight, and obese. There was a strong relation between the weight class of the adoptees and the body-mass index of their biologic parents - for the mothers, P less than 0.0001; for the fathers, P less than 0.02. There was no relation between the weight class of the adoptees and the body-mass index of their adoptive parents. Cumulative distributions of the body-mass index of parents showed similar results; there was a strong relation between the body-mass index of biologic parents and adoptee weight class and no relation between the index of adoptive parents and adoptee weight class. Furthermore, the relation between biologic parents and adoptees was not confined to the obesity weight class, but was present across the whole range of body fatness - from very thin to very fat. We conclude that genetic influences have an important role in determining human fatness in adults, whereas the family environment alone has no apparent effect.

Aetiological factors behind adipose tissue inflammation: an unexplored research area

“…However, it is still believed that an obesity-promoting environment determines whether the obese genotype will result in the obese phenotype (69,70) . Therefore it can be speculated that SNP causing a genotype associated with inflammation will also need inflammatory-promoting environmental factors to result in the obesity-inflammatory phenotype.…”

“…This association has been made obvious by studies of adoptees who resemble their biological relatives but not their adoptive relatives and by numerous twin studies, suggesting that genetics accounts for 50-90 % of the variance in BMI (69,70) .…”

Genetic influence on appetite in children

“…Evidence for the high heritability of weight both in adults and children indicates that environmental susceptibility may be genetically determined. [2][3][4] The search for genetic markers associated with higher body weights is making progress, [5][6][7][8] and this raises the issue of the mechanisms through which genetic variations affect weight. Most attention has been paid to energy expenditure and fat storage as mechanisms underlying the genetic effects.…”

Genetic contributors to obesity

“…Although the environment shared by monozygotic twins is more similar than the environment shared by dizygotic twins, the heritability of BMI is not different in identical twins reared together or apart. A genetic component to obesity has also been confirmed in adoption studies (3). These comparisons indicate that the genetic transmission of obesity is at least as large as the nongenetic transmission.…”

“…The most convincing evidence for a genetic component to obesity comes from twin and adoption studies (1)(2)(3)(4). In studies (1) in which body fat content was measured (either as body mass index [BMI] or skinfold thickness), the comparison of obesity in monozygotic twins with obesity in dizygotic twins indicated heritability quotients ranging from 0.4 to 0.98 (where 0 = no inheritance and 1.0 = complete inheritance of the trait).…”