By Caitlin Hagan, CNN
From Paging Dr. Gupta

A new study published in the journal Clinical Pediatrics has concluded that "the critical period for preventing childhood obesity...is during the first two years of a child's life and for many by three months of age."

It's the first study to identify a so-called "tipping point" in a child's development of obesity. This new finding comes as first lady Michelle Obama is targeting childhood obesity in a new national initiative Let's Move.

"We've been struggling with the older kids, ages 6 to 8, who are already way overweight," says Dr. John W. Harrington of Children's Hospital of the King's Daughters in Norfolk, Virginia. "And at that age, it's too difficult to change eating habits."

Harrington and his team set out to determine the point at which a child's weight gain becomes unhealthy and leads to overweight.

"We backtracked and said, 'When did this weight first happen?'" says Harrington. "Since the age of 3 or 4 months, these children were overweight as babies...they had normal growth but their weights were averaging well above their heights."

By identifying when the weight gain first develops, Harrington believes pediatricians will be able to intervene early to change poor eating habits in babies and toddlers on track to becoming overweight.

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