* Experts cautious about weight-loss drugs in children
* Some 40 pct of kids in US, Europe overweight in 2010-WHO
By Kate Kelland
LONDON, May 6 (Reuters) - Weight-loss surgery should only be used in the most severely obese of children, and then only with extreme caution due to the risks and the fact its effectiveness remains unknown, health experts said on Thursday.
In a review of studies on the obesity epidemic, scientists from Britain and the United States said lifestyle changes such as better diet and more exercise should always be the first option, and treatment with drugs should be used rarely.
Bariatric surgery, or weight-loss surgery, such as operations to apply gastric bands to limit the stomach size of severely overweight people, should be a last resort, they said.
"The risks of bariatric surgery are substantial, and long-term safety and effectiveness in children remain largely unknown," Sue Kimm of the University of New Mexico, Debbie Lawlor of Britain's Bristol University and Joan Han of the U.S. National Institutes of Health, wrote in The Lancet journal.
They said surgery should be reserved for only the most severely obese children -- those with a body mass index (BMI) over 50, or those with a BMI over 40 and other major health risk factors -- and "even then considered with extreme caution".
BMI is equal to weight in kilograms divided by height in meters squared. A BMI score of 30 or over is considered to be obese, and a BMI of 40 or more signals morbid obesity.
Childhood obesity can adversely affect almost every organ in the body and often has serious consequences, including high blood pressure, abnormal blood fats, insulin resistance or diabetes, fatty liver disease, and psychosocial complications.
The Lancet review highlighted data up to 2006 showing that prevalence of childhood obesity either doubled or trebled between the early 1970s and late 1990s in Australia, Brazil, Canada, Chile, Finland, France, Germany, Greece, Japan, Britain and the United States.
The rise is attributed mainly to children having a more sedentary lifestyle and eating more calorific foods.
In 2010, more than 40 percent of children in the World Health Organisation's North American and eastern Mediterranean regions, 38 percent in Europe and 22 percent in southeast Asia are predicted to be overweight or obese.
Many studies have looked at the safety and effectiveness of weight-loss surgery in obese adults, but there is less evidence about it in children.
A study published in February found that severely obese teenagers who had surgery to limit what they could eat lost more weight and enjoyed more health benefits than those who followed an intensive diet and exercise programme. [ID:nN09112489]
Lawlor and colleagues said assessments of drugs for obese children had found they produced improvements compared with lifestyle changes alone, but also had a number of side effects.
As a result, they suggested doctors should take "a very conservative approach to drug therapy" and use weight-loss drugs only for children in the highest five percent of BMI.
The weight-loss drugs studied included orlistat, which is marketed as Xenical by Roche ROG.VX and as Alli by GlaxoSmithKline (GSK.L), and sibutramine, which is sold by Abbott Laboratories (ABT.N) under the names Reductil, Reduxade and Zelium in Europe and Meridia in the United States.
The experts said prevention, especially in young children, is by far the best approach to the rising global obesity levels.
Policies encouraging parents to give their children healthy food, boost physical activity and reduce sedentary behaviour should be introduced in households, schools and communities, they said. (Editing by Elizabeth Fullerton)