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Obesity now begins in kindergarten? What new study says

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(CBS) Chubby kids might be cute, but childhood obesity is known to raise the risk for diabetes and heart disease. And an alarming new study shows that even by kindergarten age, large numbers of American kids have a body mass index (BMI) that suggests they're on the path to obesity.

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The proportion of kids who are heavy rises markedly during elementary school, with the biggest gains coming between first and third grades - and excess weight gain is particularly common among Hispanic children and black girls.

"It not just kids who are already overweight getting more and more so," study author Ashlesha Datar, a senior economist at California-based RAND Corp., told HealthDay. "There is an entire shift. Even those who are normal weight are gaining weight."

For the study - published online Nov. 21 in the journal Pediatrics - researchers pored over nine years of height and weight information on almost 6,000 white, black, and Hispanic schoolchildren participating in the ongoing Early Childhood Longitudinal Study. The researchers found that nearly 40 percent of kids began kindergarten with a BMI at the upper end of the growth charts (BMI greater than the 75th percentile).

A child with a BMI between the 85th and 95th percentiles is considered overweight, while a child whose BMI is at or above the 95th percentile is considered obese.

What's making youngsters so heavy? Experts have pointed at all sorts of possible causes, including the ready availability ofhigh-calorie snacks to video games, TV, and other examples of technology that get in the way of calorie-burning exercise.

Whatever the explanation, the finding suggests that the first few years of elementary school are a critical time for interventions aimed at preventing obesity. As the authors concluded, "Interventions aimed at preventing excess weight gain among adolescents might be too late."

The CDC has more on childhood obesity.