The results appear online Monday in Pediatrics.
The study involved 91 school-aged kids at New England summer camps. About half were given sugary cereals, the others got low-sugar cereals. Both could choose to add sugar and fruit slices.
Kids in the low-sugar group added more sugar than the others, but also more fruit. The sugary group kids ate almost twice as much refined sugar.
The researchers say the results show kids will eat healthier breakfasts with low-sugar cereals, especially if parents offer fresh fruit, and a little extra sugar, too.