In recent years, research has linked the ability to self-regulate, or rather, the lack thereof, to rising rates of childhood obesity. Indeed, less self-control in childhood is associated with worse adult health, economic and social outcomes.

However, a new study, conducted by the Ohio State University, suggests that strong self-regulation skills – that is, the ability to control and change one’s social behavior – may have less influence on the likelihood of childhood obesity than previously thought, for one group particularly: girls.

The study, published in the journal JAMA Pediatrics,found that 2-year-old girls who scored highly in self-regulation, and 2-year-old girls who scored low in self-regulation, were both at greater risk of becoming obese by age 5 than girls who had an average ability to self-regulate. Boys who exhibited higher self-regulation ability, however, were less likely to be obese than low or average scorers.

“Although we tend to assume that more self-regulation is always a positive, it may not be,” says lead author Sarah Anderson, associate professor at Ohio State’s College of Public Health.

Researchers analyzed 2001 data from the National Center for Education Statistics of 6,400 American children, examining 2-year-olds’ ability to self-regulate and its impact by kindergarten on both boys and girls. The team measured self-regulation with a four-part home assessment analyzing a child’s adaptability, persistence, attention, and frustration tolerance.

“Observers were looking at things like how readily a child gave up a block when an adult said it was time to play with something else, how difficult it was to hold their attention and how easily frustrated they became when things weren’t going their way,” explains Anderson. “Going in, we thought what many people think — that we would see lower rates of obesity as self-regulation increased.”

This was true for the boys in the study, but not for the girls. The researchers are stymied as to why.

“All we can do based on this research is speculate, but it’s possible that girls and boys are reacting differently to social expectations and that could play a role in childhood obesity,” Anderson said.

For instance, it may be more socially acceptable for a boy to become easily frustrated than it is for a girl, which can create social stress for girls. Researchers also speculate that girls are rewarded more frequently than boys for good behavior, and thus may feel more pressure to please adults, adding stress to their lives.

“These stresses might result in differences in energy balance and metabolism between girls and boys, especially in the group observed to have high self-regulation,” says Anderson.

While there is no clear cause — researchers were quick to note there are myriad potential physiological differences and behavioral responses to demands in a child’s environment that could affect appetite, food intake, sleep and activity level — the finding does suggest that focusing childhood obesity interventions on building self-regulation skills could backfire in some cases.

“Obesity prevention is a complex and humbling task. Gender is another social influence that may affect the success of obesity prevention efforts,” says Anderson’s co-author, Robert Whitaker, of Temple University.