Fathers are conspicuously absent from studies that test the best ways to prevent and treat obesity in children, according to an analysis of research done in the past decade.

Investigators focused on randomized controlled trials designed to test whether a specific intervention can directly prevent obesity or help children who are already obese lose weight.

Fathers accounted for just 6 percent of participants when only one parent was allowed to join studies of pediatric obesity, the researchers report in Pediatrics, online January 27. And when both parents could participate, 92 percent of the studies didn't provide objective data on fathers' involvement.

"Although fathers have a unique and powerful influence over their children's health and wellbeing, most research programs to date have intentionally or unintentionally recruited mothers as they are more likely to be the primary caregiver," said lead study author Philip Morgan of the University of Newcastle in Australia.

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"Of the limited research investigating the reasons why fathers are less likely to participate in parenting programs, key barriers appear to include competing work commitments, reduced awareness of programs or their unique and important role, reluctance to participate in 'mother-dominated' environments and a lack of programs that are designed specifically for dads," Morgan added by email.

For the current study, Morgan and colleagues analyzed 213 previously published randomized controlled trials assessing behavioral interventions to prevent or treat obesity in kids.

Even though fathers were largely absent from these studies, only four reports mentioned the lack of dads as a limitation of the research.

Just two studies reported explicit attempts to get more fathers to participate.

More research is needed to fully understand how the absence of fathers may influence the effectiveness of obesity interventions, or how much adding dads to these studies might benefit kids, the authors note.

It's possible that engaging fathers might also help encourage kids to get more exercise because some previous research has shown dads are generally more likely than mothers to initiate and facilitate physical activity, Morgan said.

Plus, children tend to listen better when they get the same message from both parents, Morgan added.

"In the obesity-promoting world we live in, it is also so much easier for parents to positively influence their child's behavior when they are both on the same page," Morgan said. "When both parents are modeling positive dietary and physical activity behaviors, children are more likely to follow their lead."

When mothers and fathers have different parenting styles and model different lifestyle choices, children are less likely to adopt healthy behaviors, said Jerica Berge, co-director of the Heathy Eating and Activity across the Lifespan Center at the University of Minnesota in Minneapolis.

Fathers and mothers often perceive children's weight and behaviors differently, which can also affect the outcome of research testing obesity prevention or treatment programs, Berge, who wasn't involved in the current study, added by email.

"Mothers and fathers report factors in the home environment differently, like the frequency of family meals and conversations about the child's weight," Berge said. "Thus, it would be important to include both mothers and fathers in research on childhood obesity."

The field of childhood obesity research is moving toward family-based intervention and treatment, said Dr. Sandra Hassink, medical director for the American Academy of Pediatrics Institute for Childhood Weight and a researcher at Case Western Reserve University in Cleveland, Ohio.

"The family is a system with a series of mutual interactions that depends on a common understanding of the problem, the goals and the process of treatment to be most effective," Hassink, who wasn't involved in the current study, said by email. "Research including fathers can only add to the effectiveness of treatment and prevention."