WASHINGTON — Pediatricians are supposed to track if youngsters are putting on too many pounds — but a new study found less than a quarter of parents of overweight children recall the doctor ever saying there was a problem.

Does that mean doctors aren’t screening enough kids, or aren’t frank enough in these tough conversations? Or is the real story parent denial?

The research published Monday can’t tell, but makes it clear the message too often isn’t getting through.

“It’s tricky to say, and it’s tricky to hear,” said lead researcher Dr. Eliana Perrin of the University of North Carolina, who analyzed government health surveys that included nearly 5,000 parents of overweight children from 1999 to 2008.

Parents tend not to realize when a weight problem is creeping up on their children. When almost a third of U.S. children are at least overweight, and about 17 percent are obese, it’s harder to notice that there’s anything unusual about their own families. Plus, children change as they grow older.

The new study suggests when parents do recall a doctor noting the problem, it’s been going on for a while.

About 30 percent of the parents of overweight 12- to 15-year-olds said a doctor had alerted them, compared with just 12 percent of the parents of overweight preschoolers.

Even among the parents of very obese children, only 58 percent recalled a doctor discussing it, says the report published by the journal Archives of Pediatrics & Adolescent Medicine.