Two years ago, University of Minnesota researchers reported that parent and family counseling on eating habits could reduce childhood obesity. Today, they're figuring out just why the approach worked.

Turns out, experimental counseling provided to 81 Twin Cities families was particularly effective at getting them to reduce the sizes of the dinner portions they served and to cut down on sugar-sweetened beverages at the table, according to follow-up study results released Monday.

The results suggest that meal sizes and sugary drinks are closely linked to childhood obesity, said Jayne Fulkerson, a lead author of the study from the U's School of Nursing.

Other counseling messages — such as eating more fruits and vegetables — didn't really sink in for the families, the study found. But children in the counseling group were less likely to gain unhealthy weight anyway.

"We tend to do that in research — too many messages," Fulkerson said. "I think we've learned over the five years of this study that we need to consolidate the message, not necessarily because something isn't a good message, but because people can only handle so many things."

Fulkerson's research started five years ago with a comparison of 160 families, half of whom received training called HOME Plus, which involved 10 monthly family counseling and meal-planning sessions, as well as five telephone calls to help parents set healthy goals.

Researchers checked with the families 12 months and 21 months later, and found less unhealthy weight gain among children ages 8 to 12 whose families participated in the training.

Following up on the study results and figuring out which counseling messages had the greatest impact was critical, Fulkerson said, before some version of the HOME Plus training could be offered clinically to families outside of controlled research. The study identifying the most effective messages was published in the Journal of the Academy of Nutrition and Dietetics.

At first, Fulkerson said, parents were confused about the ideal portion sizes for their children, partly because of the mixed messages of giant restaurant portions and large dinner plates.

"Kids don't need as much food as adults do," she added, "but how much is enough and how much is too much? I think people have gotten away from the clean-your-plate club, but might have second portions or really large plates" that still result in overeating.

Counseling families to eat fruits and vegetables might have other health benefits, Fulkerson said, but might not impact childhood weight if parents ended up coaxing children to eat them on top of other unhealthy items.