Lap band was initially touted as a "safer and less invasive" alternative, according to the study. And although the risk of both types of bariatric surgery is decreasing, gastric bypass is still considered the more complicated and riskier of the two with a 10 to 18 percent morbidity rate and a 0.1 to 0.3 percent mortality rate.
Although the initial effects of gastric bypass surgery on weight and diabetes may be superior to those of lap band, the long term effects are less clear.
"Having practiced bariatric surgery for 17 years, I know that gastric bypass is a great weight loss operation. My concern is that it is not a great operation for maintaining the weight loss," said Dr. Mitchell Roslin, a bariatric surgeon at Lenox Hill Hospital in New York City.
Roslin said people who had gastric bypass surgery regain an average of 15 percent of their weight within three years -- an effect that may be due in part to a return of inter-meal hunger, he said.
"As a result, we are seeing many patients five to ten years from surgery who have regained 50 percent or more of the weight they have lost. With this, there is a return of some of the medical problems that seemed to have resolved," Roslin said.
Last week, the FDA expanded the lap band eligibility criteria to include people with a BMI over 30 who have at least one related health condition, such as diabetes. It's estimated that another 25 million Americans now qualify for the procedure.
Dr. Bruce Wolfe, professor of surgery at Oregon Health and Science University in Portland and president of the American Society for Metabolic and Bariatric Surgery said he thinks the FDA should have lowered the obesity bar for lap band even further to include people with a BMI between 30 and 35 who have a related health condition and people with a BMI between 35 and 40 with no related health problems. His rationale: Obesity is a disease that shortens life and is associated with a long list of related health conditions, and is therefore appropriate to treat effectively.
Previously, people with a BMI under 35 were ineligible altogether.
But the expanded criteria is unlikely to cause a surge in lap band procedures, Wolfe said. One reason is that insurers aren't yet covering the procedure in newly-eligible patients, meaning they would have to pay out-of-pocket.
"The insurance companies may require a higher level of evidence than is required by the FDA for approval of a device," Wolfe said.
But even among eligible, potentially insured patients, the surgery rates are low, Wolfe said.
"We estimate that less than 2 percent of the eligible population actually undergoes surgery in a year," Wolfe said. "Most of the people who are eligible are not receiving surgery now."
ABC News' Jane Allen contributed to this report.