Overweight and obesity are the major cause of Type 2 (adult onset) diabetes. According to the U.S. Centers for Disease Control and Prevention (CDC) the rate of type 2 diabetes has tripled in the last 30 years -- largely to the global obesity epidemic.

Obesity and type 2 diabetes are causally linked. Weight gain leads -- through several mechanisms -- to insulin resistance. Insulin resistance places a greater demand on the ability of the pancreas to produce insulin, leading to the development of clinical diabetes.

Fat accumulation also induces insulin resistance through changes in its hormonal and other secretions. As fat cells increase, particularly in the abdomen, metabolically toxic secretions increase while protective hormones such as adiponectin decline. Physical inactivity, both a cause and consequence of obesity, also contributes to insulin resistance.

Analyses undertaken by the International Obesity Task Force for the World Health Report 2002 indicate that approximately 58 percent of type 2 diabetes can be attributed to overweight and obesity.

However in Western countries, around 90 percent of cases of type 2 diabetes are attributable to weight gain, and childhood obesity is now leading to an unusual increase in type 2 diabetes among adolescents.

For adults, clear evidence indicates that weight loss can reverse type 2 diabetes and relatively modest weight reductions can markedly reduce the development of diabetes if not prevent it completely.

The effect of weight loss through diet and increased activity on diabetes has been demonstrated in the National Institute of Diabetes and Digestive and Kidney Diseases Diabetes Prevention Program, and it particularly benefits those susceptible to diabetes over 60 years of age.

Dietary and activity changes to produce a weight loss of five to seven percent of body weight can successfully reduce the incidence of type 2 diabetes. Reductions in fat and calorie intake accompanied by half an hour's extra walking or other exercise each day lowered the incidence by 58 %.

Great success has been achieved among people over 60 years, reducing the development of diabetes in that high risk age group by 71%. Similar data have emerged from China, Scandinavia and other European studies