The National University Hospital (NUH) is conducting a trial to look at how bariatric or metabolic surgery can benefit severely obese people who have diabetes.
It plans to recruit 30 patients who are Singaporeans or permanent residents, said the study's co-investigator, Dr Asim Shabbir, director and senior consultant at NUH's Centre for Obesity Management and Surgery.
The patients will need to have a BMI (body mass index) of 32.5 to 50. The healthy BMI level for Asians is between 18.5 and 22.9.
Obesity is a major risk factor for Type 2 diabetes, which accounts for most diabetes cases. Diabetes occurs when a person's blood sugar level is too high and it can lead to blindness, kidney failure, stroke and other complications.
The effects of two common types of bariatric surgery will be studied. One is laparoscopic sleeve gastrectomy, or gastric sleeve, which involves removing a portion of the stomach.
The more complex Roux-en-Y gastric bypass surgery is done such that food will bypass the stomach.
Studies have shown that these procedures can lead to significant weight loss, which helps to keep blood sugar levels in check. But research has largely been focused on Caucasians, who tend to develop Type 2 diabetes later than Asians.
Dr Shabbir said: "We need to improve our understanding of the physiological changes that follow weight loss surgery in obese Asians patients with diabetes."
Asian patients tend to have a lower BMI and higher percentage of fat per BMI unit than those from the West.
Dr Shabbir, who is also president of the Obesity Metabolic Surgery Society of Singapore, said the study results would show obese diabetics that surgery can be an effective tool as well as help guide doctors on which of the two procedures would best serve their patients' needs.
"We want to see what is changing after surgery that helps patients to lose weight as well as improve their diabetic control," he said.
Bariatric surgery, he said, will lead to changes in gut bacteria and the way the body disposes of extra energy, for example, in the form of heat. It will also modify eating behaviour and change how the brain perceives food.
"After surgery, the patients' choice of food may change and they may not like carbs anymore or they may prefer less sweet food."
Without surgery, weight loss with dieting can be difficult to sustain.
"A person with 100kg of excess weight may see a drop of 10 to 20 per cent with diet and exercise. But if the drop is any bigger, his body will react by increasing his appetite and decreasing his energy expenditure," he said.
The NUH trial is a one-year study that may be extended to look at long-term changes as well.
In Singapore, bariatric surgery is meant for patients with a BMI of above 32.5 if they have obesity- related illnesses like diabetes, or a BMI beyond 37.5 if they have none.
Khoo Teck Puat Hospital is also conducting a trial to see whether bariatric surgery or medical therapy, including drugs, can help Asian patients with a BMI of 27 to 32 and uncontrolled Type 2 diabetes manage their condition better. It is looking for more people to come forward.
A similar trial by the Cleveland Clinic in the United States ended recently. Five-year findings showed that bariatric surgery is more effective than medical therapy in treating mild and moderately obese patients for Type 2 diabetes.
More than 88 per cent of the surgically-treated patients maintained healthy blood glucose levels without the use of insulin. Those who had surgery also saw significantly greater weight loss than those who were on medication.