An adoption study of human obesity

Area of Science:

• Human genetics
• Obesity research
• Behavioral genetics

Background:

• Understanding the interplay between genetics and environment in determining human body weight is crucial for public health.
• Previous studies have suggested both genetic and environmental factors contribute to obesity.
• Adoption studies provide a unique model to disentangle genetic and familial environmental influences.

Purpose of the Study:

• To investigate the relative contributions of genetic factors and the family environment to human fatness in adults.
• To determine if genetic influences on body mass index (BMI) are present across the entire spectrum of body weight.
• To assess the impact of the adoptive family environment on adult adoptee weight.

Main Methods:

• Analysis of 540 adult Danish adoptees from a larger cohort, categorized into four weight classes: thin, median weight, overweight, and obese.
• Comparison of adoptee body-mass index (BMI) with the BMI of their biologic and adoptive parents.
• Statistical analysis to determine the significance of correlations between parental BMI and adoptee weight class.

Main Results:

• A strong positive correlation was found between the weight class of adoptees and the body-mass index (BMI) of their biologic parents (P < 0.0001 for mothers, P < 0.02 for fathers).
• No significant relation was observed between the weight class of adoptees and the BMI of their adoptive parents.
• The genetic influence on BMI was evident across all weight classes, from thin to obese individuals, not limited to obesity alone.

Conclusions:

• Genetic factors play a significant role in determining adult human fatness.
• The family environment, as represented by the adoptive family, appears to have no discernible effect on adult body fatness.
• These findings highlight the substantial heritability of body mass index in the adult population.