There are no outward physical signs of insulin resistance. A glucose tolerance test, during which insulin and blood glucose are measured, can help determine if someone is insulin resistant. Many people who are insulin resistant produce large enough quantities of insulin to maintain near normal blood glucose levels. No one knows for sure. Some scientists think a defect in specific genes may cause insulin resistance and type 2 diabetes.
Researchers continue to investigate the cause.
Science has not yet determined why some people with insulin resistance eventually develop diabetes and others do not. By maintaining an appropriate weight and a physically active lifestyle many individuals are able to reduce their chances of becoming insulin resistant and developing diabetes. Research indicates that low fat diets may aggravate the effect of insulin resistance on blood lipids. Specifically, they recommend decreasing fat intake to less than 30 percent of calories. Some groups recommend even lower levels of dietary fat.