Many of the people who've undergone obesity surgery have discovered a positive side-effect to having the stomach-sizing operation: a significant improvement in their diabetes.

In many cases, patients who are already on medications for Type 2 diabetes are able to stop them before they leave the hospital, says Dr. John Hagan, a bariatric surgeon at Humber River Hospital in Etobicoke, Ont.

He says in almost 75 per cent of these obese patients, the surgery — either gastric bypass surgery or laparoscopic banding — reverses their diabetes, often instantly.

"The diabetic patients often leave hospital off all their diabetic medications even before they've had a chance to lose weight," he told CBC News.

Dr. Arya Sharma, scientific director of the Canadian Obesity Network, goes farther in his assessment. "I would almost use the word 'cured.'"

Heather McInnes was diabetic and on medication when she weighed 337 pounds. Four months ago, she had gastric bypass surgery, a procedure in which a portion of the stomach is surgically stapled to create a smaller pouch, and then attached to the intestines.

McInnes's blood sugar levels have been normal ever since and her self-esteem is soaring. "I probably am not beautiful to everybody — but I'm beautiful to me," she says. "I feel great."

Experts don't fully understand how obesity surgery is able to reverse Type 2 diabetes so quickly and even before weight loss begins. Calgary-based endocrinologist Dr. David Lau says it may be that the surgery triggers hormonal changes that affect insulin resistance. 

Insulin resistance occurs when normal amounts of insulin produced by the body are inadequate to produce a normal insulin response from fat, muscle and liver cells.

"I think we're still in the early days of learning how bariatric surgery can really help to keep diabetes in check," says Lau.

Surgery less expensive than obesity costs

About two million Canadians have Type 2 diabetes, according to the Canadian Diabetes Association. They are at higher risk of heart attacks, kidney failure, blindness and amputation.

The costs of treating these conditions is an estimated $8 billion a year in Canada.

Obesity surgery, on the other hand, carries a one-time cost of about $16,000 per patient.

But health experts do caution that the surgery is not for everyone. Though they say it is safer than it once was, there are still risks, such as one death in every 200 to 300 surgeries, blood clots, leaking at one of the staple lines in gastric bypass surgery and intolerance to certain foods.

Plus, some patients can't commit to the new health regime they must follow after surgery. "A lot of patients who come seeking surgery are probably not going to do well because they cannot make those lifestyle changes that patients have to make to be successful with obesity surgery," says Sharma.

Those challenges are ahead for Jackie Mohammadi, an Ontario resident who is set to soon have gastric bypass surgery. Suffering from a host of health problems, she hopes to leave the hospital without any symptoms of diabetes.

For now, diet and exercise are still the first-line treatment for most people with Type 2 diabetes.

But for the morbidly obese, some experts say surgery may be the most important intervention since the discovery of insulin.