The children were divided into three groups depending on when they reached their BMI rebound age -- early, middle and late. The BMI rebound age for children in the early group was 4.4 years for boys and 4.2 years for girls. In the oldest group, the rebound age was 6.6 years for boys and 5.7 years for girls.
By the time they turned 7, children with an earlier BMI rebound age had higher blood pressure, higher blood insulin and leptin levels, and larger left ventricular and left atrial size. The ventricle and the atrium are chambers of the heart.
"Girls' rebound age was a little bit younger than boys, and that potentially can mean they are at an increased risk to be obese," Kimball said.
The study authors also found that children today, overall, had younger rebound ages than a generation ago.
Why is BMI rebound age so critical? "I don't know for sure, but it's probably because you just have a longer period of time that you're gaining weight," Kimball said. "The earlier you start, the more you're being exposed to being obese."
It's unclear if the problem is reversible, but teenagers who underwent gastric bypass surgery and lost large amounts of weight (60 to 70 pounds) saw their left ventricular size decrease, the researchers said.
"There needs to be education. I don't think even pediatricians or physicians are necessarily even measuring BMI," Kimball said. "We know what to do: Diet and exercise. It's the same old thing, and it's frustrating getting people to actually practice it."
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