The link between parents' body mass index and their children's body mass index in childhood is driven largely by genetic inheritance rather than by direct biological effects of parental weight during pregnancy, according to a study published on June 23. The collaborative international research was conducted by the universities of Bristol and Queensland and the Norwegian Institute of Public Health, with findings released in PLOS Medicine.
Researchers analyzed data from the Norwegian Mother, Father and Child Cohort Study, which included information on 86,000 children born between 1999 and 2009. This dataset provided details such as birth weight, BMI from six months to eight years old, and appetite-related eating behaviors at age eight. By examining twin, sibling, and half-sibling relationships across generations, the researchers aimed to determine how much of the parent-child BMI association could be attributed to genetic factors.
The study found that maternal BMI was more strongly associated with offspring birth weight than paternal BMI. However, after birth both maternal and paternal BMI showed similar associations with offspring BMI from age two to eight. Models indicated that genetic effects explained an estimated 79% of the statistical association between a mother's BMI and her child's BMI at age eight, and 94% for fathers. Higher parental BMI was also linked to obesity-related eating behaviors in children.
Dr. Tom Bond said, "Obesity runs in families, but it is difficult to work out why this is. Our results suggest that the link between a mother's or father's body mass index (BMI) and their children's BMI up to age 8 is mostly due to inherited genes. Expectant parents should be encouraged to maintain a healthy weight, but this may not be enough to ensure that their children also have a healthy weight." Alexandra Havdahl added, "Our findings suggest that the link between parents' and children's body mass index is driven largely by shared genes rather than by the intrauterine environment or parenting behavior."
The research team cautioned that these findings do not support the idea that childhood obesity is inevitable for children of heavier parents; environmental factors still play a role in gene expression related to body mass index. They also noted that maternal health during pregnancy remains important for perinatal outcomes.
