TOKYO — Kyodo News

Expectations for obesity surgery are rising in Japan where about 600,000 people are reported to be overweight.

Severely overweight people account for 0.5% of the country’s population in terms of the body mass index, a measure of body fat calculated by dividing weight in kilograms by height squared in meters. A BMI score of 35 or more is considered morbidly obese.

Treating obesity can involve gastric bypass surgery, in which the stomach is divided to restrict food intake, according to medical experts.

The annual number of surgical procedures to treat obesity is around 340,000 in the rest of the world. The number in Japan is about 100 but it represents a gradual increase.

In anticipation of a future rise in the number of surgical procedures, the Japanese Society for Treatment of Obesity announced guidelines at a meeting in Tokyo in July, designating people with a BMI score of 35 or more and those suffering complications from illness with a score of 32 or more as requiring treatment.

Japan is said to lag behind other advanced countries in terms of surgical procedures for morbidly obese people, with about 300 conducted up to fiscal 2006, according to a survey compiled by Iwao Sasaki, a professor at Tohoku University who specializes in surgery and a former president of the society.

However, an additional 205 surgical procedures were performed at eight medical facilities in the last two years.

Isao Kawamura, honorary director of Kamagaya General Hospital in Chiba Prefecture, who conducted the first surgical procedure on a severely overweight person in Japan at Chiba University in 1982, said such operations are necessary because the number of severely overweight people is increasing in the country.

‘‘Obesity is hard to cure,’’ said Yasushi Saito, director of the society and president of Chiba University. ‘‘Even those who manage to reduce their weight fail to keep it off.’’

He called for practitioners in the fields of medicine, surgery and psychiatry as well as nutritionists and nurses to cooperate to treat obese people for sustained periods.

Severe obesity is a serious issue in the United States. About 400,000 people reportedly die of obesity each year, says the U.S. Centers for Disease Control and Prevention. It said obesity is the second biggest cause of preventable deaths in the country after smoking.

Surgical procedures for obesity became possible in the mid-1990s with the introduction of the laparoscope to examine the abdomen. Such procedures have become commonplace in the United States and Canada, which are said to account for two-thirds of all such operations in the world.

Former sumo champion Konishiki underwent surgery in Hawaii in February last year and succeeded in losing more than 120 kilograms.

He said he weighed 303 kilograms at one time, adding that his life has changed following the operation.

The recorded death rate among people who have undergone surgery is much lower in the seven years following an operation compared with those who have not received surgery, according to a follow-up survey conducted in the United States and European countries.

The Japanese Society for Treatment of Obesity is expected to start registering surgical procedures for the treatment of obesity and to make the figures public before the end of the year.