The quality of life for severely obese children and adolescents is roughly equivalent to that of pediatric cancer patients undergoing chemotherapy, according to a new study.

The research compared very overweight children to ones who were healthy and others who had cancer, and found that obesity colored nearly the entire spectrum of physical, social and emotional activities. Most very overweight children have at least one medical complication and miss four times as much school as normal-weight children. They're also more likely to report feeling socially isolated even though they aren't clinically depressed or anxious, which most of them aren't.

"It was a dramatic finding, but not an entirely surprising one," said Jeffrey B. Schwimmer, a pediatrician at the University of California at San Diego, who led the study, which was published today in the Journal of the American Medical Association. "Obesity is an extremely socially stigmatized disease, and unlike some conditions, it's not something a child can hide."

Morgan Downey, director of the American Obesity Association, an advocacy group, said the research "reinforces a lot of other studies. . . . We know that there are profound psychosocial effects from obesity." He called the findings "depressing."

Overweight and obesity are growing at near epidemic rates in the United States. The fraction of children ages 6 to 19 who met the definition of overweight ranged from 4 percent to about 7 percent in the 1960s and 1970s. It jumped to 11 percent in the late 1980s and 15 percent in the late 1990s.

The new research studied a group of children and adolescents referred to the UCSD medical center for treatment of obesity who were at the extreme end of the overweight group -- representative of perhaps 2 to 3 percent of all American children.

The average 12-year-old in the study, for example, was 5 feet 1 inch tall and weighed 175 pounds. In comparison, the average 12-year-old American boy is 4-foot-11 and weighs 90 pounds, with a 12-year-old girl an inch taller and two pounds heavier.

The researchers asked the 106 children -- roughly half boys, half girls -- to answer how much of a problem ("never," "almost never," "sometimes," etc.) various activities were. These included "participating in sports or exercise," "taking a bath or shower by myself," "other kids not wanting to be my friend," "keeping up when playing," "paying attention in class" and "missing school because of not feeling well." They were also asked about their emotional state -- how often they felt "sad or blue" or worried "about what will happen to me."

They compared the survey results to those previously collected from healthy children at pediatricians' offices, and children with cancer who were getting, or had recently gotten, chemotherapy. The maximum possible score was 100.

The average score of the healthy children was 83. For the cancer patients, it was 69. For the severely obese children, it was 67.

The biggest gap between the healthy children and the obese children was in questions on social functioning -- a 20-point difference. This was also the biggest difference between the cancer patients and the obese children, with the latter reporting a 9-point lower score than the cancer patients.

"Many children with cancer may experience teasing and withdrawal from peers at school because they appear different," Schwimmer said. "At the same time, there are probably some children that are more sympathetic toward them.

"While not all children are going to be mean to obese children, it's unlikely that many are going to be sympathetic to their plight. And certainly many children do tease them in ways that can be very hurtful."

About 65 percent of the very obese children had at least one ailment associated with their condition, though often it was a condition that doesn't cause symptoms. About 4 percent had diabetes and 37 percent had elevated cholesterol and other bloodstream lipids. About 13 percent had depression or anxiety, a slightly higher rate than among children overall.

One of the more surprising findings was that the overweight children missed an average of four days of school in the month before filling out the survey, compared to less than a day in the healthy children.

"Traditionally, the field of education has not taken obesity to be an educational problem, but a social and health one. That may have to be reexamined in light of these findings," said Downey, of the American Obesity Association.

Schwimmer said he and his co-authors -- Tasha M. Burwinkle, also of UCSD, and James W. Varni of Texas A&M University -- were especially surprised by the magnitude of the problems reported by the overweight children.

"Many of these children are not going to come to their parents or physicians and tell them, 'I am experiencing all these problems.' But our data suggest that the likelihood of this being true is quite high. In order for these children to receive appropriate services, the problem needs to be recognized."

The overweight children had an average body mass index (BMI) of 35. Overweight is defined as a BMI of 25 to 29.9, and obesity as a BMI of 30 or more. BMI is calculated on the basis of height and weight.

The current issue of the journal is devoted to obesity research. It includes reports on three drugs that helped people lose weight when used in addition to other interventions, such as diets and behavioral counseling.