TUESDAY, Feb. 1 (HealthDay News) -- Weight gain is common after children have their tonsils removed, an analysis of four decades of research concludes.

Researchers from Saint Louis University found that 50 percent of the children in the studies gained more weight than expected as part of normal development, according to study lead author Dr. Anita Jeyakumar. While not "hugely surprising," the findings are important to consider in light of the obesity epidemic and the frequency of tonsillectomy, she said.

"About 30 to 50 percent of this generation of children is overweight so anything that can exacerbate that should be looked at very closely," said Jeyakumar, a pediatric otolaryngologist at Saint Louis University Medical School.

Although fewer tonsillectomies are performed today than 40 years ago, it is still one of the most common major surgical operations performed on U.S. children, she pointed out. Doctors and parents should take the study findings into account when deciding if a child needs the procedure, said Jeyakumar, also an assistant professor of pediatrics.

The analysis, published in the February issue of Otolaryngology -- Head and Neck Surgery, included nine studies on tonsillectomy alone or tonsillectomy with adenoidectomy (removal of the adenoids) published between 1970 and 2009. The 795 children involved were 18 years of age or younger and ranged from normal weight to morbidly obese. The research was divided into three sections based on how weight was measured, and the participants were followed for an average of one year.

The first group, with 127 patients, measured body mass index (BMI). On average, the BMI of children in that group increased about 7 percent after surgery and was 3.6 percent greater than a control group's.

The second group, with 419 children, used standard U.S. height and weight charts. Weight gains were noted in 46 percent to 100 percent of this group, the researchers found.

Various methods were used to assess weight in the third group, involving 249 patients. From 50 percent to 75 percent of those children gained more weight than expected based on growth and development, according to the analysis.

A small number of children in the studies lost weight after the surgery, the study found.

The small number of studies included in the research reflects inconsistencies in the recording of medical information, which makes comparisons difficult, the authors noted.

The tonsillectomies were performed on children who had repeated infections, or sleep-disordered breathing, which disturbs sleep and disrupts breathing briefly but repeatedly. The condition is sometimes linked to frequent infections of the upper respiratory system.

Jeyakumar cautioned that the study did not show why the children gained weight or even prove that the reason they did was because they had tonsillectomies.

Theories about post-tonsillectomy weight gain suggest that children who were hyperactive prior to surgery became calmer and more focused afterward, thus using fewer calories, according to research cited in the study. Children with disturbed sleep probably burned more calories as they struggled to breathe, other research suggested. Both conditions are common in children with chronic tonsillitis.

Another theory cited is that parents may tend to "over-feed" children recovering from surgery.

"The main thing is that no one should panic," Jeyakumar said. "Every patient needs to be evaluated individually, and parents need to be aware. It doesn't mean the child shouldn't have the surgery" if weight is a problem.

Another expert agreed, saying that the study wouldn't change his practice. "If I send a child for surgery, he needs surgery," said Dr. Dennis Woo.

"When these kids gain weight after surgery it can be for a number of reasons. We can be hard-pressed to sort through it and say 'it's mostly this, or mostly because of that,'" said Woo, an associate professor of pediatrics at the University of California Los Angeles David Geffen School of Medicine.

But this study "would be another reason to be sure that surgery is necessary for a child," he said.

For children with breathing-related problems, the authors suggest trying continuous positive airway pressure (CPAP) before resorting to surgery. Also, doctors should make dietary and lifestyle recommendations for young tonsillectomy patients, they say.

Another recent report, published in January 2011 by the American Academy of Otolaryngology--Head and Neck Surgery, provided new guidelines for doctors determining the need for tonsillectomies. The guidelines advise antibiotics and a "wait-and-see" approach for moderate cases, noting that these cases usually resolve over time.

More information

The Nemours Foundation has more about tonsillectomy.