What works?

Julie Bernard is equally pleased with the diet and exercise program she started around the same time. Like Williams, Bernard was worried that her extra pounds plus diabetes would doom her to ill-health as she ages.

“I went into the program hoping to feel better,’’ said Bernard, 49, of Duxbury, who has lost 16 pounds so far.

Both women are participating in a pilot study by the Joslin Diabetes Center and Brigham and Women’s Hospital designed to help patients with diabetes improve their health while reducing medications. Roughly half the 100 people in the SLIMMT2D study will get surgery — either gastric bypass like Williams, or a stomach banding procedure — and half will start with the 12-week “Why WAIT?’’ program at Joslin that was created in 2005 to treat obese patients with diabetes, and which Bernard completed at the end of June.

The goal of the SLIMMT2D study, designed to follow patients for three years, is to figure out which route is safer and more effective over the long term, particularly for diabetics who have weight to lose but are not severely obese. Typically, bariatric surgery — surgery for the treatment of obesity — is reserved for people who have a body mass index (BMI) above 35, with at least 80-100 pounds to lose. For these subjects, the health risk of excess weight is considered far greater than the risk of surgery.

But as the surgical risks have fallen and the benefits confirmed for diabetics — particularly for those getting gastric bypass — doctors want to know whether lighter-weight people would also benefit from surgery, said Dr. David Lautz, director of bariatric surgery at the Brigham and the study’s co-principal investigator along with Dr. Allison B. Goldfine of the Joslin.

The purpose of the trial is “to say in a very preliminary way, does bariatric surgery make sense at a lower BMI or are you better off doing something very aggressive medically?’’ Lautz said.

Nearly 8 percent of Americans — 24 million people — have type 2 diabetes, making it hard for their bodies to turn food into energy. Usually triggered by obesity, type 2 diabetes results in high levels of blood glucose, which can lead to serious health complications.

For reasons that researchers have yet to fully understand, bypass, in which a surgeon reconfigures the digestive system to bypass the lower stomach and upper small intestine, seems to change patients’ metabolisms almost immediately, said Dr. Janey S.A. Pratt, codirector for surgery at the Massachusetts General Hospital Weight Center. These metabolic changes seem to improve glucose control while also promoting weight loss by reducing hunger and boosting feelings of fullness, said Pratt, who is not involved in the Joslin-Brigham study. Stomach banding, in which restrictions are placed around the stomach to promote earlier fullness, appears to improve diabetes only as weight is lost.

Both types of surgery will be compared against the Joslin’s aggressive lifestyle and medication modification program, developed by Dr. Osama Hamdy. Medical director of the obesity clinical program at Joslin, Hamdy is very optimistic — giddy even — about the benefits of Why WAIT? Patients who have previously gone through the program have lost an average of nearly 25 pounds and kept off more than 18 for a year, according to research published by Joslin in 2008. Hamdy said newer findings show they kept almost all that weight off for three years — “the longest, to my knowledge, weight loss that we have ever seen in clinical research,’’ he said.

More than 80 percent of the patients also met their diabetes targets; their kidney and liver functions improved, and their blood pressure fell, said Hamdy, who is also an assistant professor at Harvard Medical School. They were able to reduce their diabetes medication by 50-60 percent, saving an average of $560 a year per person.

Joslin also switches Why WAIT? participants off older diabetes medications that can trigger weight gain, Hamdy said. And building and maintaining lean muscle is a big focus of the program, because muscle burns more energy than fat. Participants are encouraged to do strength training as well as aerobic activities, and they are told to eat more lean protein and fewer carbohydrates.

“The whole idea here is how we can modify the amount of body fat in a way that can help diabetes significantly,’’ Hamdy said.

Bernard said that before she heard about the SLIMMT2D trial, she “had pretty much given up,’’ on the idea of losing weight. “I just bought bigger suits.’’

She was taking the maximum amount of oral medication she could — the next step would have been insulin injections. She had watched her parents both struggle with diabetes for years, and her illness was progressing far faster than theirs had.

Now, lighter and exercising four to five hours a week again, she’s excited about her progress.

“It was a fabulous experience,’’ Bernard said. “I’m a lot more knowledgeable about my diabetes, which I think is helping my overall health.’’

Williams, the bypass patient, said she is also committed to living a healthier lifestyle now, eating less and exercising more. When she goes out to a restaurant, she and her husband — who’s always been trim — share one entree. If she feels the need for dessert, she samples his instead of getting her own.

“I wanted to make sure I’m looking just as good as he’s looking,’’ she said, chuckling. Now, “I think that’s the case.’’

She stopped needing insulin injections almost immediately after her surgery and her goal for the next few months is to get off diabetes medications entirely and dial back on her cholesterol and blood pressure drugs, too. If she can do that, she’ll save more than $1,000 a year in copays, she said, at a time when — as a 55-year-old — she’s starting to think about retirement.

To learn more about the study or participate in it, e-mail BWHSLIMMT2D@partners.org or call 617-525-7388.

Karen Weintraub can be reached at karen@KarenWeintraub.com.