The frontier in the fight against childhood obesity should be pushed back to toddlers and preschoolers, a new study suggests. The researchers found that kids ages 3-5 already have developed a taste for sugary, fatty, and salty foods, and easily recognize the brands that offer these options.

The university researchers found that very young children, once exposed to foods with high sugar, fat and salt contents, develop a palate for those foods, which are usually higher in flavor than their healthier alternatives, but are also the foods most closely linked to childhood obesity.

The study was comprised of two experiments. In the first, 67 children and their parents were asked a series of questions about what foods the children liked. Foods with added flavor, such as chips, ketchup and chocolate milk, were favorites among the children, and parent responses confirmed their children’s affinity for foods with high amounts of sugar, salt and fat.

The second experiment examined whether marketing affects children’s preferences for unhealthy foods. One hundred eight children were shown pictures of fast food and soda, and asked to determine whether the product was made by Brand A, Brand B, or not offered in fast food stores. The study found that children who were able to match the most foods and drinks with their brands were also those whose parents reported their children as having the strongest preference for sugary, fatty and salty foods.

In other words, children exposed to fast foods and soda were more likely to favor these flavors over others.

All of the 3-5-year-olds were able to match some foods with the brands that serve them, and some turned out to be experts.

“It’s amazing to sit down a 3½ or 4-year-old and have them get 90 percent right,” says Dr. Bettina Cornwell, a marketing professor at the University of Oregon and co-author of the study.

Cornwell explains that, in a vicious cycle, marketers want to promote foods that appeal the most to consumers. Consumers choose more flavorful foods over their blander competitors, but these foods rely on sugar, fat or salt to achieve a bigger flavor pop.  As people buy more of these unhealthy products, their palate for sugary, fatty and salty foods increases, which creates further incentive for marketers to push them.

“They’re in a war against each other of being more flavorful, more extreme,” she says.

The study reports that children partial to these more flavorful foods are also more likely to add extra flavors, such as condiments or salt, to existing food to get an even bigger “flavor hit.”

Cornwell says the study’s biggest implication is that the fight against childhood obesity needs to start at a young age, and start at home.

“If we want to influence the obesity epidemic, we have to start earlier. If we wait until school age, a child’s palate is probably developed,” she says. She explains that once children arrive in a new environment like school, they will choose what they know and like. If they prefer sugary, fatty and salty foods, they’ll be likely to ignore the salad bar altogether.

The study suggests reducing kids’ exposure to unhealthy foods so that they don’t develop a taste for big flavor kicks. Cornwell says the rule to remember is “repeated exposure leads to preference formation,” so the goal is to eliminate opportunities for exposure.

The study recommends putting foods high in sugar, fat or salt out of sight of young children. “Little kids are great about that kind of stuff,” Cornwell says. “Out of sight out of mind.” The same principle applies to food advertising. The less kids see ads for foods, the less they’ll demand those foods.

Not sure where to draw the line on what you let your kid eat or watch? Cornwell has some novel advice: “Interview them.” Ask your own child what makes them want to eat certain foods. “They’ll tell you all about it,” she says.

The study was conducted by Cornwell and Anna McAlister, a professor at the University of Wisconsin, Madison. An early version was released in the journal Appetite. The final version is due to be released in print soon.