A comparison of four types of Obesity surgeries, all risky procedures, concluded that vertical gastrectomy, in which most of the stomach is removed, was both the quickest and resulted in the most weight loss, researchers said on Monday.

While all types of obesity-related surgery are seen as risky and a last option for most obese people, particularly older patients, vertical gastrectomy was preferred over three other methods evaluated in a yearlong study of 166 patients over the age of 50.

Vertical gastrectomy removes up to 95 percent of the stomach and leaves behind a thin tube-like stomach roughly 2 ounces (60 milliliters) in volume.

Patients who underwent this surgery lost an average of 133 pounds (60 kg) after one year, 15 pounds (6.8 kg) more than the next-best surgical method.

The other three types of surgery in order of the average amount of weight loss that resulted were Roux-en-Y gastric bypass, in which most of the stomach is sectioned off by a line of staples and part of the small intestine bypassed to inhibit the absorption of calories; duodenal switch, in which a large portion of the stomach is removed and the small intestine rearranged; and lap-band surgery, in which a silicone band is placed around the upper section of the stomach to shrink the stomach’s size and slow the exit of food.

“It is important for us to know, especially as these surgeries become more prevalent, which operation is best for each patient,” study author Paul Cirangle of the California Pacific Medical Center said in a statement prepared for delivery to a conference of gastrointestinal and other experts in Chicago.

Vertical gastrectomy surgery was performed in the shortest amount of time - about 90 minutes - and had the fewest complications, the study found.

A second study presented at the conference by Venezuelan researchers suggested that many gastrointestinal surgeries could be performed by inserting an endoscope down the patient’s throat rather than by slicing through the abdomen.

“Since the abdominal wall is never cut, the surgery and recovery time is much faster,” lead investigator Roberto Fogel of the Hospital de Clinicas in Caracas said.

All types of gastric bypass surgery carry risks that include wound infections, post-operative vomiting, vitamin deficiencies, and bleeding in the lungs. Some studies estimate that one to two patients out of 100 die following the surgery.

The number of gastrointestinal surgeries performed has multiplied in the past decade alongside a rise in the number of morbidly obese people, an estimated one in 20 Americans. In 2003, 103,000 such surgeries were performed in the United States compared to fewer than 20,000 annually in the early 1990s.

Obesity increases the risk of a host of health problems such as Heart disease, Diabetes and several types of cancer.

At the same meeting two teams of researchers presented findings that obese patients had higher risks of benign colon tumors - a precursor to Colon cancer - and esophageal cancer.

But obese patients who lost weight over a year significantly reduced their risk of colon tumors compared to those who did not lose weight, researchers at the University of Tokyo said.