The Report on America's Children, by the National Institutes of Health, the Census Bureau and other agencies, shows the number of overweight children aged 6 to 18 has more than doubled since 1980.
There are now an incredible 20 million obese children in America.
Edward Sondik, director of the National Centre for Health Statistics, said that the girth of America's children is a major concern.
"In 1980, six percent of children aged 6 to 18 were overweight. For 2000, it is 15 percent. That's two-and-a-half times what it was just 20 years ago,” he said.
"Even more striking than that, if you look at the figures for black children, 22 percent of them are overweight. And among Mexican-American children, 25 percent are overweight."
He added that doctors are now finding diabetes and heart disease in children, when 20 years ago those were only adult diseases.
Analysts say that the obesity epidemic among children has been caused by a combination of poor diet and a sedentary lifestyle.
However, it isn't all bad news about America's children
Dr Duane Alexander, director of the National Institute of Child Health and Human Development, said the report also contradicts some strongly-held beliefs about the nation's kids.
He said: "Half the American adults surveyed believe that teen pregnancy is getting worse.
"In fact, teen births have declined every year since 1991. For girls aged 15 to 19, the birthrate fell from 62.1 percent per 1,000 teens in 1991 to 43 per 1,000 in 2002.
"This is a statistic that is moving in the right direction."
Violent crime down
He added that violent crime among teens is down, too.
"Most people, about two-thirds, believe that crime is going up among America's children," he said. "But the picture painted by this report, based on actual data, paints the opposite picture."
The report says victims reported 17 violent crimes per 1,000 juveniles aged 12 to 17, or 413,000 juvenile crimes in total.
"This is a 67 percent drop from the 1993 high and the lowest rate recorded since the national victimization survey began in 1973," the report reads.
Meanwhile, smoking and alcohol use is also down among most groups, the report finds.
Among eighth-graders aged 13, 14.5 percent reported they smoked every day, about the same as 2001. Among 12th graders 17 percent did, a decline of two percent from last year.
And from 2001 to 2002 the percentage of 10th- graders who reported binge drinking fell to 22 percent from 25 percent. But the proportion of 12th-graders, aged 17 and 18, stayed steady at 29 percent.