A major reason for the increase? American kids are eating more than they should.
A new study finds that kids are snacking more than ever - nearly three times per day - and this has added 168 calories to their daily diets since 1977.
Researchers at the University of North Carolina, Chapel Hill analyzed decades of eating behavior among kids and found that snacks now comprise 27 percent of the calories in children's diets.
And they aren't choosing healthy foods either. Since the late 70s, kids are snacking on less fresh fruit and milk and more junk food such as cake, candy and chips.
Experts say the excess calories are bad, but it's the high sodium and fat content in these snacks that may be truly damaging for kids' health in the future.