A new study shows the percentage of kids who have ever struggled with a chronic illness grew to 52 percent between 2000 and 2006. And researchers said it's due to all the extra weight many kids carry.

More than half of kids ages 8 to 14 have some kind of problem like a learning disability, asthma or other disease.

Childhood obesity also doubles the risk of premature death.

In fact, another new study shows hefty kids have a greater likelihood of not even living to see their 55th birthday. This could pose a problem in the future as about a third of kids and teens in the U.S. are obese or overweight.

The latest study is one of the most comprehensive since it followed a group of kids well into adulthood with research spanning several decades.