THURSDAY, June 16 (HealthDay News) -- Obese patients whose body-mass index (BMI) falls below the minimum level recommended for weight-loss surgery may have better outcomes than those who are more obese, new research suggests.

An analysis of data from nearly 1,000 patients revealed that those patients whose pre-surgery BMIs were below the federal guideline threshold of 35-plus experienced a 100 percent remission from type 2 diabetes in the year following surgery.

In contrast, the remission rate for type 2 diabetes in obese patients with a BMI of 35 or more was about 75 percent.

"There was a clear trend that as your weight was lower when having gastric bypass surgery, your outcomes were actually better," noted study co-author Dr. John Morton, director of bariatric surgery at Stanford Hospital & Clinics at Stanford University in Palo Alto.

"This finding suggests that perhaps we should be getting patients to surgery sooner than later, before their weight goes too high and the surgery comes less effective," Morton said.

"After all, when we talk about patients below a BMI of 35, we're not talking about people who are just pleasantly plump," Morton added. "These are people with real, substantial risks associated with excess weight, particularly with respect to diabetes, which has a lot of negative consequences."

Morton and his colleagues are slated to present their findings Thursday at the American Society for Metabolic & Bariatric Surgery annual meeting, in Orlando, Fla. Because the study has not been published in a peer-reviewed journal, its findings should be viewed as preliminary.

Guidelines from the National Institutes of Health recommend gastric bypass only for patients whose BMI is 35 or more and who have an obesity-related condition (such as high blood pressure, sleep apnea, joint disease and/or metabolic syndrome) and who have not been able to lose weight through less invasive methods.

For someone with a BMI of 40 or more, an obesity-related disease is not necessary to qualify for weight-loss surgery, according to NIH guidelines.

Morton noted that ideally one's BMI should clock in under 25. For a woman with a height of 5-foot-4, this would roughly equate to weighing about 140 pounds.

A woman of the same height who weighs 200 pounds would actually fall just short of the BMI threshold of 35, he said, while at 300 pounds the same woman would have a BMI of nearly 52.

Morton explained that the current study came about almost accidentally, as a result of a Stanford pre-surgical program designed to educate prospective patients about the surgery and to encourage them to adopt better nutritional habits before the operation.

Out of the 980 obese patients who had met the NIH criteria when they were initially slated for surgery between 2004 and 2010, 12 patients actually showed up for the procedure at BMI levels below the recommended cut-off point for surgery.

The result: a year following surgery, those patients with a BMI under 35 not only experienced better outcomes in terms of diabetes, but lost more weight than those who met the recommended BMI threshold for weight-loss surgery. They also showed more improvement in obesity-related conditions in addition to diabetes.

At check-ins from three-months to a year after surgery, the patients who weighed less than that recommended for gastric bypass had also lost more weight than those with the higher BMIs. At the 12-month mark, they had lost 167 percent of their excess weight, in contrast to those with a BMI of 35 to 40 (112 percent), 40 to 45 (85.3 percent), and 50 (67 percent).

The authors also noted that the time it took to perform the gastric bypass procedure itself was also shorter for those with lower BMIs.

"What we found amounts to what I think is a big lesson: we ought to intervene with these patients earlier than previously thought," said Morton.

Like all operations, weight-loss surgery is not without risk. Complications include serious infections, internal bleeding and blood clots, and the risk of dying is one in 1,000, according to the American Society for Metabolic & Bariatric Surgery.

Weight-loss surgeries are also expensive, costing about $20,000 to $25,000 or more, depending on the procedure.

Dr. David M. Kendall, chief scientific and medical officer of the American Diabetes Association, approached the findings with some caution.

"While these are exciting and interesting findings, it is really the first set of evidence that looks at this specifically," he said. "We need more research with larger groups and for longer periods of follow-up before we can really start ringing the bell."

"More generally, the other thing I would add is that while bariatric surgery has on several occasions shown impressive results across various bands of weight, people need to be reminded that even modest weight loss and improved glucose control in the absence of surgery can help immensely in terms of diabetes control" and prevention, Kendall said.

More information

For more on bariatric surgery, visit the National Institutes of Health.