Some scientists have speculated that the current generation of children will be the first in the history of America to die earlier than their parents did - and a recent study reveals cereal ads may be partly to blame.

Most American preschoolers watch 642 cereal commercials a year.

The majority of the ads are for cereals with the worst health ratings: 85-percent more sugar, 65-percent less fiber and 60 percent more sodium than cereals marketed to adults.

The worst contain up to 44 percent sugar, according to a new Yale University study.

"If one looks at the rank order list of the worst nutrition cereals, it's stunning how the worst cereals are marketed so aggressively to children," the study's author Kelly Brownell said.

Kids also often visit cereal Web sites with alluring cartoons, games, and music all centering on the cereals kids want. So parents buy - leading to childhood obesity, critics say.

A number of cereals dubbed unhealthy in the study have "better-for-you" labels, a marketing strategy that stems from cereal companies meeting new, healthier, self-imposed regulations.

One example of the cereal industry policing itself is the reduction of sugar from 3.5 to 3 teaspoons per serving. Technically, it can be marketed as lower sugar, but health experts insist that's still far too much.

Nevertheless, cereal companies are continuing to defend their products.

"Well I don't know how they came to their conclusion that they are the least nutritional products. Because children's cereals that are advertised in our program are low in calories, they're chock full of vitamins and nutrients," industry spokeswoman Elaine Kolish said.

Still, while the cereal makers stand by their products, critics say it's candy disguised as breakfast.