The fattening of the rich world has sparked a surge in demand for surgery to help people lose weight, a European specialist said on Saturday.

Most people can drop excess pounds or kilos through exercise, eating less or medication, but for the most obese and people suffering a weight-related disease, this may not suffice.

Dr Martin Fried, of the Laparoscopic-Obesity Treatment Hospital in Prague, told a medical conference more patients are opting for surgery to cure their obesity. “Demand is increasing because people are getting fatter and are better informed,” he said.

Weight-loss surgery restricts the food a person can consume or interferes with calorie absorption by shrinking the stomach with bands or staples or bypassing part of the organ.

Up to 50,000 operations have been performed each year in Europe and many more in the United States where the surgery was invented and developed.

Only the most severely overweight - the technical term is morbidly obese - or people close to that category but have a serious illness linked to obesity, such as high blood pressure or diabetes, qualify for the surgery.

Morbidly obese people have a body mass index (BMI) of 40 or more - equal to being about 100 pounds or 50 kg overweight.

BMI measures weight in relation to height. It is calculated by dividing weight in kg by height in meters squared. A healthy person will have a BMI of 25 or under.

For people above a certain weight, diet and exercise are unlikely to lead to sustained weight loss and surgery may be more effective. “Of the morbid obese about 30-40 percent would qualify for surgery,” said Fried.

Gastric bypass surgery is one of the most popular types of weight-loss surgery in the United States. In Europe, Fried said gastric banding, in which a silicon band is placed over the top of the stomach during keyhole surgery to decrease its capacity, is more common.

“It is a straightforward operation and takes from one hour to do,” he said.

Average weight-loss within the first 18 months after surgery is about 40 kg (90 pounds) and the complication rate is about five percent, compared to 12 percent with gastric bypass surgery, and the mortality rate is minimal, according to Fried.

“Non-surgical treatment fails in maybe 70-80 percent of patients. Surgical treatment is successful in around of 70-75 percent of patients,” he added.

About 2,500 doctors, researchers and clinicians are attending the four-day European Congress on Obesity in Prague.