Previous studies have shown that parents who eat more fast food and spend more time on the couch have kids who do the same. And moms and dads who let their kids watch more TV or spend hours in front of the computer also have children who are heavier and more likely to be obese.

Until now, there hadn’t been a close look at how overall parenting style—how permissively or authoritatively parents interact with their kids on everything from homework to chores and getting along with their siblings—might affect children’s weight. “We looked at the general way that parents can affect their child’s obesity even if they are not trying to control specific health-related behaviors,” says the study’s lead author, Lisa Kakinami, a postdoctoral fellow at McGill University.

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She and her colleagues followed a group of more than 37,000 children in Canada aged zero to 11 years, and asked parents about their interactions with their youngsters. The team queried parents about things like how they responded when their child did something they shouldn’t, and how much they praised their kids when they did something positive.

Based on their responses, Kakinami and her colleagues focused on two of the four well-established groups of parenting styles: authoritative, in which parents set rules and boundaries but explain their reasoning and show understanding when the rules are broken; and authoritarian, in which parents set strict rules but aren’t as open to discussing and explaining them to their children. (The others, at the opposite end of the spectrum, are uninvolved, in which parents communicate very little with their children and are virtually absent as authority figures; and permissive, in which parents make few demands and expect little self-control from their kids.)

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Kakinami found that children of authoritarian parents were 30% more likely to be obese at 2 to 5 years old, and 37% more likely to be obese if they were 6 to 11 years old compared with children of authoritative parents.

While the study wasn’t designed to tease apart what might be contributing to the higher body mass indices (BMI) in the authoritarian households, pediatricians have some theories. “When a parent says absolutely ‘no,’ that becomes forbidden fruit, and kids may then value that more,” says Dr. Stephen Daniels, chair of pediatrics at the University of Colorado, who was not involved in the study, about certain kid-favorite foods such as sweets, soda and fast food that are high in calories.

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Kakinami says there were hints that other factors may be at work as well. Authoritarian parents were less likely than authoritative moms and dads to praise their children or give them positive feedback for good behavior, regardless of whether it was related to their health. “The main difference in authoritative vs. authoritarian styles is the warmth expressed between the parent and child,” she says. “Authoritative parents ranked higher on praise than authoritarian parents.” And when their children misbehaved, authoritarian parents were “most likely to respond emotionally and punish the child but not tell them what they had done wrong.”

Kakinami acknowledges that the study, which she is presenting at the American Heart Association’s Epidemiology & Prevention/Nutrition, Physical Activity & Metabolism meeting, is only a first step toward understanding how overall parenting style can influence children’s weight. It’s possible, for example, that other factors related to parenting style – education or stress – could be the driving force in the association between iron-fist parenting and children’s obesity. (Kakinami and her team did control for some variables, including poverty, and found that the link persisted.)

How malleable parenting styles are is still an open question as well. Studies in which authoritarian parents are trained to adopt a more authoritative style might reveal whether the connection is a robust one, says Daniels.

In the meantime, the results suggest that setting boundaries but making sure that children understand why rules are in place can teach them self-control, which might be important in regulating their eating habits as well. “Since we are all concerned about how to prevent obesity from developing in the first place, these kind of data are helpful to direct us toward thinking about important risk factors and how to address them,” says Daniels.

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