The number of American children with chronic illnesses such as obesity has nearly quadrupled in a generation, doctors say.

Wednesday's theme issue of the Journal of the American Medical Association focuses on chronic childhood illnesses that last a year or more after diagnosis.

In 1960, about 1.8 per cent of U.S. children and teens reported a chronic health condition that limited their activities, which jumped to seven per cent in 2004, Dr. James Perrin, a professor of pediatrics at Harvard Medical School, and his colleagues reported.

The main three chronic health conditions for American children were:

• Obesity, which affects an estimated 18 per cent of children today, up from five per cent in the 1980s.
• Asthma, with a prevalence of nine per cent now, nearly double that of two decades ago.
• Attention deficit hyperactivity disorder, an increase linked to better diagnosis.

"A chronic condition in a child will become a chronic condition in an adult," pediatrician Dr. Catherine DeAngelis, the journal's editor-in-chief, told a teleconference with reporters on Tuesday.

"What you're talking about for an adult is maybe 10, 20 years of suffering. But with a child, you're talking about maybe 50, 60 years of suffering."

Lifestyle changes a family issue

Another study suggested overweight children who participated in an intensive lifestyle change program with their families were more likely to succeed than those who had individual counselling.

When nearly 210 inner-city children aged eight to 16 were randomly assigned to a program combining nutrition education, behaviour modification and tailored exercises, their body mass index, body fat composition and total cholesterol improved more than those in a control group who went to a pediatric obesity clinic.

"This is a family problem," said study author Mary Savoye, a registered dietitian at Yale University in New Haven, Conn., who attributed the success of the program to frequent contact between families and staff. "The child can't do it alone."

While the control group gained an average of 17 pounds, the weight management group stayed about the same.

The exercise portion of the program included 50 minutes of exercise for two nights a week, such as participating in relay races and obstacle courses for eight to 10 year olds, or flag football and basketball for the older group.

British association debates child protection measures

A similar British program called MEND teaches overweight children the basics of healthy eating, such as trying new vegetables, and exercise. Most participants lost weight, learned what to eat and kept the weight off.

Also on Tuesday at the British Medical Association's annual conference, delegates debated taking severely obese children from their parents as a child protection measure. The majority decided it was an important health and welfare issue, but not one for doctors to decide.

About one in four British children is overweight. In comparison, about 20 per cent of children in Canada were considered overweight, according to a 2004 Canadian Community Health Survey.