When insulin levels are high, certain tissues are overloaded with fatty molecules, which leads to insulin resistance. It has been common practice to increase the insulin dosages for many obese patients who have insulin-resistant type 2 diabetes in an attempt to lower their high blood glucose levels and overpower that resistance.

While insulin in high doses may lower glucose levels, it will also increase the fatty molecules and may cause organ damage.

The National Heart, Lung, and Blood Institute recently halted part of an ongoing clinical trial on diabetes and heart disease after more than 250 people died while receiving intense treatment to drive their blood glucose levels below current clinical guidelines.

Lifestyle Changes Outpaced Evolution

Recent research has delivered compelling evidence that links insulin resistance to excess accumulation of fatty molecules in liver and muscle, wrote Dr. Roger Unger, professor of internal medicine and a diabetes researcher at UT Southwestern Medical Center, in the commentary.

Intensive insulin therapy is contraindicated for obese patients with insulin-resistant type 2 diabetes because it increases the fatty acids that cause diabetes, he warned. Dr. Unger has investigated diabetes, obesity and insulin resistance for more than 50 years and is a member of the National Academy of Sciences.

The most rational therapy for obese patients with insulin-resistant type 2 diabetes eliminates excess calories, thereby reducing the amount of insulin in the blood and the synthesis of the fatty acids stimulated by the high insulin. Giving more insulin simply increases body fat.

The increase in the number of patients with insulin-resistant type 2 diabetes can be traced to the epidemic of obesity that began in the US after World War II, Dr. Unger says in his commentary. Food preparation was moved from the family kitchen to factories and companies that produce high-fat, calorie-dense foods, leading both men and women to consume substantially more calories on a daily basis.

In addition, increasingly widespread use of technological advancements such as televisions, computers and automobiles has reduced the number of calories burned per day.

"Evolution was unprepared for the change in the American diet to processed fast food and drive-through lanes," said Dr. Unger. "There's no way that our genes could evolve to gird themselves against the superabundance of very, very high-calorie foods that have flooded the US."

Before the discovery of insulin, starvation was the only treatment for diabetes, he noted.

Excess Fat Is the Culprit

"Today there are many treatment options, including bariatric surgery, if necessary, to lower the fat content in the body before you start giving insulin," he said. "The fat is causing insulin resistance and killing the insulin-producing beta cells in the pancreas -- that is what is causing type 2 diabetes."

Giving more insulin simply channels the glucose into fat production. There is now a spectrum of therapies for diabetes that correct insulin resistance by reducing body fat. Insulin treatment would be indicated only if all these fail.

"Giving more insulin to an insulin-resistant patient is akin to raising the blood pressure of a patient with high blood pressure to overcome resistance to blood flow," Dr. Unger said. "Instead, you would try to reduce the resistance."

Type 2 diabetes occurs when the body is unable to make enough of the hormone insulin to compensate for insulin resistance. The condition affects between 18 million and 20 million people in the US.

Factors that increase the risk of type 2 diabetes include obesity, age and lack of exercise. Over a period of years, high blood sugar damages nerves and blood vessels, leading to complications such as heart disease, stroke, blindness and kidney disease.