Having two obese parents may substantially raise a child’s risk of becoming obese, with mom’s weight playing a particularly important role, a new study suggests.

UK researchers found that among more than 7,000 2- to 15-year-olds in a national study, those who had two obese parents were 12 times more likely to be obese than children with two normal-weight parents. That was with factors such as socioeconomics - gauged by parents’ jobs - and ethnicity taken into account.

Mothers’ weight showed a particularly strong association with children’s weight, the study found.

The findings, published in the American Journal of Clinical Nutrition, are not the first to connect parents’ obesity to their kids’ risk, or to highlight the role of mothers’ weight. What’s different is that the researchers had measurements of parents’ weight and height, and did not have to rely on self-reports.

“The main contribution is that we had objective measures, and that allowed us to be confident that the mother-child association is stronger than the father-child association,” senior researcher Dr. Jane Wardle, a professor of clinical psychology at University College London, told Reuters Health by email.

The results are based on data from 4,432 UK families who took part in an annual national health survey between 2001 and 2006. A study nurse measured each participant’s weight and height, and parents and children were classified as normal-weight, overweight, obese or severely obese based on their body mass index - a measure of weight in relation to height.

In 38 percent of the families, at least one parent was obese, while 8 percent had two obese parents. Only 14 percent of families were headed by two normal-weight parents.

Child obesity was uncommon in families with two normal-weight parents, at roughly 2 percent. But in families with two obese parents, 22 percent of kids were also obese; when both parents were severely obese, 35 percent of children were obese.

Paternal and maternal weight were each connected to children’s risk of being obese. Among children with an obese father, 12 percent were obese themselves, versus 4 percent of those with normal-weight fathers. Of children with an obese mother, 14 percent were obese, compared with 3 percent of kids with a normal-weight mother.

When the researchers did a statistical analysis controlling for the other parent’s weight, they found that mothers’ weight showed a statistically stronger association with children’s weight than did fathers’.

The reasons for that finding are not certain, according to Wardle. However, she said, mothers may be relatively more important because their weight and diet during pregnancy affect fetal development - and may, research suggests, help set a child’s future appetite regulation and weight.

Mothers’ weight may also be a bigger factor than fathers’ because moms are typically the ones who take charge of the children’s diets, Wardle and her colleagues note.

“Given that rates of severe obesity are rising rapidly in many countries,” Wardle and her colleagues write, “effects on childhood obesity are likely to be dramatic.”

They say their findings highlight the importance of intervening early to prevent the “intergenerational transmission” of obesity.

Parents who are obese, Wardle said, should be aware of their children’s increased risk and try to encourage healthy eating and regular exercise. That, she noted, includes improving their own lifestyle habits so they can serve as a role model for their kids.

SOURCE: http://www.ajcn.org/cgi/content/abstract/ajcn.2009.28838v1 American Journal of Clinical Nutrition, online April 7, 2010.