The World Health Organization warns a global epidemic of obesity is causing a global epidemic of diabetes. This year's theme for World Diabetes Day calls attention to the large number of diabetics who die and become disabled because of lower limb amputations that the agency says are preventable.

The World Health Organization estimates more than 170 million people around the world are suffering from diabetes and this number is expected to double in 25 years.

WHO says type 2 diabetes, which accounts for the vast majority of the disease, is largely preventable. WHO Diabetes Expert, Bruce Unwin, says people who are overweight or obese are at great risk of getting the disease.

"This is the type of diabetes that is increasing everywhere in the world where studies have been done, whether it is in the United States or United Kingdom or urban centers in Africa or India," he said. "Because as lifestyles change, and as we know, obesity is increasing all over the world, then this type of diabetes is becoming more and more common."

Dr. Unwin says there is good evidence that people can dramatically reduce their risk of getting diabetes by losing weight and becoming physically more active. He says this in turn also will reduce their risk of stroke, heart disease and kidney failure, conditions that are associated with diabetes.

Diabetes mellitus is a chronic disease caused by the body's inability to produce insulin, or by the ineffective use of the insulin produced. This deficiency results in increased concentrations of glucose in the blood, which in turn damage many of the body's organs.

A common problem linked to diabetes is the loss of lower limbs. Dr. Unwin says many diabetics will experience numbness in a foot. Because of this diminished sensation, he says people often do not feel pain in the foot until it is actually damaged.

"And that can be from something like standing on a pin and not feeling it and then infection gets into the foot and it is not recognized until it is too late, until it has done quite a lot of damage," explained Dr. Unwin. "Or it can mean that it is possible to wear poorly fitting shoes which also do damage to the foot, but that is not picked up because like most people who would feel it, it would feel uncomfortable and painful. But, if you are not getting that sensation, then you can do damage that then leads to further problems."

The World Health Organization says more than half of all diabetic foot and lower leg amputations can be prevented with adequate detection and care. It says simple measures such as regular foot examination and wearing comfortable shoes can save a limb.