The prescription diet drug Xenical (orlistat) can help control blood glucose levels in overweight and obese diabetics beyond the impact of weight loss alone, according to a report by German researchers presented at the International Congress on Obesity in Sydney, Australia.

In their analysis of seven studies of overweight and obese patients with type 2 diabetes, the researchers said they found that improvement in glycemic control for those taking Xenical was "greater than expected based on weight loss alone.

"This is the first study to demonstrate Xenical's independent effect on glycemic control and it confirms that Xenical could play a major role in the management and prevention of diabetes," the researchers said.

One of the most common problems associated with excess weight is type 2 diabetes. More than 90 percent of all people with type 2 diabetes are overweight, and excess weight is well recognised as the most important modifiable risk factor for the development of diabetes.

Unfortunately, many people with type 2 diabetes find it difficult to lose weight as some diabetes medications can cause weight gain.

"There is clear evidence to show that if weight is controlled, type 2 diabetes can be prevented or reversed," said Professor Stephan Jacob of the Institute for Cardiometabolic Preventive Medicine in Germany.

"Now we have additional grounds to recommend Xenical -- not only does it reduce weight in people with type 2 diabetes, but it independently improves glycaemic control beyond the impact of weight loss alone," Jacob concluded.

A half-strength over-the-counter version of Xenical called Alli is currently awaiting approval by the U.S. Food and Drug Administration for sale without a prescription.