Children who consume junk food during their preschool years are slower learners than those who eat unhealthily a few years later, researchers said.

A study of 14,000 children has found a large number of children who ate snacks like potato chips, lollipops and take-out food at age 3 lagged behind the rest of their class in elementary school.

The U.K. study found about 25 percent of the children who consumed a higher-than-average amount of junk food at age 3 were 10 percent less likely to keep up with their classmates in their first four years of elementary school.

The University of London researchers also found that if a child had eaten a lot of junk food at an early age, switching to a healthier diet a couple of years later would do little to improve their test scores.

“Early eating patterns have implications for attainment that appear to persist over time, regardless of subsequent changes in diet,” the researchers said.

“There was no relationship between school meals or packed lunch consumption and later attainment once the junk food dietary pattern prior to school entry and other confounding factors were introduced in the analysis.”

The researchers called on governments to take note of the study when discussing childhood obesity.

The study was published in the latest edition of the Journal of Epidemiology and Community Health.

Click here to read more from news.com.au.