That's because children in the study were randomly assigned to have surgery or to "watchful waiting" -- putting off surgery and staying with other options, such as medications to better control any nasal allergies or asthma symptoms.
Altogether, 204 children aged 5 to 9 were assigned to have surgery right away, while 192 stuck with watchful waiting. Katz's team found that over seven months, children who underwent surgery showed a quicker average weight gain, versus kids in the comparison group.
It was a small difference overall, Chakravorty said. And for children who were normal weight, there was no major effect.
"It's not making normal-weight children obese," Chakravorty noted.
But there was a clearer impact on kids who were overweight before surgery. Of those children, 52 percent had become officially obese seven months after surgery, compared with 21 percent of overweight children in the watchful-waiting group, the study found.
There are a few possible explanations for the post-surgery weight gain, according to Katz's team. Calorie-burning may dip when children are no longer laboring to breathe during sleep. And some kids may burn fewer calories during the day because they become less active after their sleep apnea improves. (Paradoxically, poor sleep often causes children to be "hyperactive," rather than drowsy, Katz explained.)
Sleep apnea itself also causes metabolic changes, Katz said. Growth hormone is released at night, and the sleep disorder can interfere with that. So the body may adapt metabolism in an effort to maintain a child's growth.
"When the sleep apnea is relieved, they're set up for rapid weight gain," Katz said.
It was once common for children with sleep apnea to be underweight and have "failure to thrive," Chakravorty noted. For those kids, rapid weight gain after tonsillectomy can be a good thing.
But these days, with childhood obesity on the rise, many kids with sleep apn
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