Insulin Resistance

What is insulin resistance?

Over the past 20 years, Americans have cut their fat intake from 36% to 32% of their average daily calorie intake, according to Dr. James Hill, of the Center for Human Nutrition at the University of Colorado.  “Nevertheless, they also gained about eight pounds per person,” said Hill. Why is this happening?

The presence of insulin resistance in the population was described, as a result of studies done by Gerald Reaven, MD, of Stanford University Medical School who studied insulin for more than 30 years.  He noted that the susceptibility of individuals varies greatly.  Researchers estimated that at least 25% of the United States population may be insulin resistant, which is in addition to those who are diagnosed as Type 2 diabetics.  Insulin resistance is a condition commonly seen in overweight persons.  The result is that insulin is not able to help carbohydrates get into the body cells (primarily in muscles) to be used for energy.  The muscle cells then call for more insulin which ultimately results in too much insulin in the body (hyperinsulinemia).

The question is, which comes first, insulin resistance or obesity?  Is an individual insulin resistant which makes that person more susceptible to storing fat, or does storing fat make a person insulin resistant?  Probably both are true.  For individuals with chronic weight problems, i.e., always having to “watch their weight” or gaining and losing 50 – 100 pounds more than once, a genetic predisposition to insulin resistance or carbohydrate intolerance is likely.

A Defect at the Cellular Level?

As the cellular receptors become less responsive to insulin, the entry of carbohydrates into the body’s cells is retarded.  Insulin is responsible for a wide range of metabolic activities including the determination of how much glucose will be used immediately for energy and how much will be stored as fat.  It may also regulate triglycerides, and perhaps the stimulation of appetite.  According to Reaven, insulin resistance may be a cluster of problems which is now defined as Metabolic Syndrome .  Insulin resistant people can develop glucose intolerance or pre-diabetes, high insulin levels, high triglycerides, low HDL cholesterol (the good cholesterol), hypertension, and Type 2 diabetes, as well as obesity.

What are the Consequences?

Individuals who are insulin resistant are often not symptomatic.  Insulin resistance, and the resultant impaired glucose tolerance, are highly prevalent in the population, but often unrecognized. By the time it is recognized in the form of Type 2 diabetes, an individual may have suffered major artery damage and may also have high blood pressure, obesity, hypoglycemic symptoms, hunger, and frustration with failure at attempts at weight loss.

How is it diagnosed?

The “gold standard” for making the diagnosis is the insulin clamp, which is an invasive, expensive research technique.  However, by using blood tests and circumstantial evidence, the condition of insulin resistance can be inferred.  Lab tests include: low HDL cholesterol, less than 30 mg/dl; high LDL cholesterol, greater than 160 mg/dl; elevated triglycerides, over 110 mg/dl; elevated blood pressure, over 135/85; diagnosed with type 2 diabetes.  Circumstantial evidence of insulin resistance is often the easiest predictor:  chronic dieting or obesity; family history of obesity and/or type 2 diabetes in parents or grandparents, aunts and uncles; siblings and/or offspring who are overweight, diabetic, alcoholic or suffer from occasional depression; central obesity.

Insulin Resistance and Hyperinsulinemia

Hyperinsulinemia and insulin resistance are terms which are currently used almost interchangeably. The confusion may have something to do with one being a cause and one a result, and if so, which comes first? Insulin resistance is a relatively new diagnosis. While there is much documentation and literature to describe it, there is still much to be learned about it. It has recently been described as another type of diabetes, which might be true if diabetes is considered an impairment in getting glucose into the cells. It is the opposite, however, of Type 1 diabetes, where the pancreas does not produce enough insulin to deliver glucose from the blood stream into the cells. Insulin resistance is characterized by an overproduction of insulin by the pancreas in an attempt to lower the blood sugar by getting it into cells. The exact mechanism for the overproduction of insulin is not totally clear. What is becoming increasingly clear is that it is not a benign state. It has consequences that can cause major disease states.

How does it relate to food?

We have helped hundreds of individuals with the laboratory and family history findings described above.  We prescribe a “controlled carbohydrate” plan where a variety of foods are prescribed, but the carbohydrate foods are limited to 2 – 3 servings per meal, depending on the caloric level of the meal plan. (These carbohydrates are fruits, breads, pasta, cereal, sweets, starchy vegetables such as corn, peas and potatoes)  This plan involves a balance of food–proteins, carbohydrates, vegetables, and milk eaten all at the same time, with limited fats, of course.  This program helps many people lose weight and it is critical for weight maintenance.

Low calorie diets using meal replacements as well as a modified fast combining formula and one balanced meal per day, all work very well.  While they are described as ketogenic, meaning that the body burns fat, they do so by controlling or reducing the circulating insulin levels in obese people.  When there is a high level of circulating insulin, fat cannot be broken down.  Therefore, controlling insulin levels helps to reduce body fat, which is critical to reducing the risk of heart disease.

For individuals who lose 50 pounds, but ideally still have 20 – 30 pounds to lose, it is critical to follow a structured eating plan.  Returning to eating a high carbohydrate diet at this stage will surely cause re-gain of the lost weight.  Therefore, a low carbohydrate diet, exercise and behavior-modified lifestyle plan are critical.

Some of the books in the popular press currently suggest a similar approach as the above discussion.  These include The Zone Diet, Protein Power, Sugar Busters, the New Atkins Diet Revolution, and the South Beach Diet.  The Zone Diet suggests 40% carbohydrate, 30% protein and 30% fat as the recommended diet composition.  For insulin resistant individuals, balancing each meal in approximately these percentages is probably a workable plan.  This is the best way to keep feeling good, to keep you appetite under control, keep your emotions stable and not get into the vicious cycle of hunger.

Maintaining control of your body’s physiology is the key to maintaining your weight loss.  A high carbohydrate, low-fat diet, as prescribed by many weight loss programs, will not work well for insulin resistant individuals.