Overall, most of the kids lost weight on the diets, Kirk noted.
Cathleen Davis, a clinical dietitian and nutritionist who works with children at Good Samaritan Hospital Medical Center in Babylon, N.Y., applauded the study and explained why the diets might have differed in popularity.
She said the portion-controlled and low-glycemic diets are probably better tolerated "because they both are more mainstream diets that the parents would be familiar and comfortable with."
What should you do if you'd like to put your child on a diet?
"Ask your pediatrician about local reputable programs and look on Eatright.org to find a registered dietitian serving your area," Davis said. "Make tiny changes and expect bad days -- absolutely no one eats perfectly 100 percent of the time. And be very careful of programs that push supplements, make any type of claim for immediate success and don't have licensed credentials."
The study was released online March 1 in advance of publication in an upcoming print issue of the Journal of Pediatrics.
For more about kids and obesity, try the U.S. Centers for Disease Control and Prevention.
SOURCES: Shelley Kirk, Ph.D., R.D., dietitian, assistant professor of clinical pediatrics, University of Cincinnati College of Medicine, and center director, HealthWorks!, Cincinnati Children's Hospital Medical Center; Cathleen Davis, M.S., R.D., clinical dietitian/nutritionist, Good Samaritan Hospital Medical Center, Babylon, N.Y.; March 1, 2012, Journal of Pediatrics, online
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