WASHINGTON — Commercials promoting sugary breakfast cereals could be put on a strict diet under government guidelines urging food companies to limit marketing of unhealthy products to children.

Under a proposal announced today by several government agencies, companies would be urged to only market foods to children ages 2 through 17 if they are low in fats, sugars and sodium and contain specified healthy ingredients.

The guidelines set parameters that are stricter than many companies have set for themselves and, if the companies agree, would eliminate much of the advertising consumers see now — on television, in magazines, in stores and on the Internet — for foods that appeal to children.

If many companies sign on to the guidelines, children could see much less of the colorful cartoon characters used to advertise cereals or other gimmicks designed to draw their attention. If the companies wanted to continue that advertising, they would have to reduce unhealthy ingredients in their products.