A surprising new factor that may influence children's eating habits and future weight is how many siblings they have.
Only children have less healthy eating habits than their peers in multi-children homes, according to a new study published Nov. 6 in the Journal of Nutrition Education and Behavior.
Researchers at the University of Oklahoma Health Sciences surveyed the eating habits, body mass index, and other demographic information of 68 families, including 27 with single children.
They found that only children were more likely to have unhealthy eating habits like consuming more refined grains, empty calories, and sugary drinks than their peers with siblings. They were also more likely to have higher BMIs, meaning they were more likely to be overweight or obese.
Previous research including 12,700 European children found that children without siblings are up to 50% more likely to be overweight than those with siblings, and the current study may help researchers understand why.
"It's not just about the child," Chelsea Kracht, co-author of the study and post-doc researcher at Pennington Biomedical Research Center, told Insider. "The child's family situation is also what people need to think about with children's nutrition."
Children's weights and eating habits are closely linked to those of their parents
Researchers found that a major factor in children's weights, and eating habits, was the health of their mothers. Moms with higher BMIs were more likely to have children who were also heavier, according to the study. This is in line with previous research linking parental BMI with children's weight.
However, this association was found to be more pronounced in only children, according to Kracht.
The study also found mothers of only children were more likely to have higher BMIs than mothers of multiple children. This was a surprise to researchers, according to Dr. Kracht.
"Conventional wisdom would say that if you have more children, more pregnancies would give you fewer opportunities to lose weight," she said.
But more children doesn't necessarily mean healthier families, Kracht cautioned.
"What we don't want is people to think that having more children will somehow make you healthier," she said. "There were children with siblings who were overweight and only children who were perfectly healthy, so that's not the case."
Researchers said families with multiple children might have healthier mealtime habits
What might help explain the difference between families' weights and health habits is mealtime routines, the researcher speculated. Having more kids likely requires a bit more work on the part of parents to orchestrate family meals, which could translate to less fast food or other convenience items, and fewer empty calories.
"Parents who have multiple children do something different, and maybe that's more preparation, scheduling, and organization," Kracht said.
However, the study notes that many other complicated factors could relate to children's BMI and lifestyle factors, including how much time they spend at daycare. Only children were more likely to spend time at childcare, away from home, which could also account for changes in eating habits, Kracht said.
The study results also can't translate to more diverse groups, since a majority of the study's participants were white and non-low-income, and both family income and race have been linked to health disparities, including eating habits and BMI.
Kracht said future research is needed to addresses how all these complex factors might play a role in eating habits of only children.