According to McGarry, in the progression from being overweight to being obese, the liver becomes resistant to insulin and the hormone’s ability to suppress hepatic (liver) glucose production. “Under these conditions, the hyperinsulinemia turns the liver into a ‘fat-producing factory’ with all of its negative downstream effects.”4 Once established, these disturbances in lipid metabolism are devastating to blood sugar balance and weight management. Accel-eration of the cycle and eventual collapse of pancreatic insulin production herald the appearance of diabetes.
The answer to how these metabolic derangements begin may lie in the “thrifty gene hypothesis,” which postulates the presence of a genetic factor designed to promote extra fat deposition.12 Speculation also suggests a defect in the leptin-signaling system, a metabolic pathway that appears to mediate fatty acid metabolism in muscle tissue and acts as a kind of “fuel gauge” to monitor cellular energy status.13 (Leptin, a chemical messenger produced by the adipose, or fat-storing, cells of the body, initiates the breakdown and oxidation of stored fat.)14 Still other research points to the possible development of functional resistance to the actions of the leptin hormone itself.15,16
Whatever the mechanism, a diminished capacity to oxidize fat appears to be a pre-eminent clinical marker for insulin resistance.17-19 This is supported by animal studies, which confirm that dietary lowering of muscle triglycerides improves insulin sensitivity and reverses diabetes.20,21 The fact that two of the most effective preventive programs for diabetes are diet and exercise lends credence to the argument that onset of the disease involves a profound disturbance in lipid dynamics.
Assessing Your Risk for Diabetes
The previous clinical definition of insulin resistance syndrome required evidence of insulin resistance. Disturbances in glucose metabolism, however, develop relatively late in the disease’s progression. Consequently, under the old definition, many people in the early stages of insulin resistance went undiagnosed.
The new definition, developed recently by the US National Cholesterol Education Panel, incorporates five easily measured variables:
- abdominal obesity
- elevated fasting blood
- triglyceride levels
- low levels of HDL (“good”) cholesterol
- high fasting blood sugar levels
- high blood pressure.
Under the new definition, a person with any three of these conditions is classified as having insulin resistance syndrome. To assess whether the new criteria could predict excess risk for heart disease and diabetes, researchers found that the risk of coronary heart disease—and, more strikingly, diabetes—rose as the number of metabolic abnormalities increased. Men with four to five features of the syndrome had almost four times the risk of coronary heart disease and 25 times the risk of diabetes compared to those with no abnormalities. The study also confirmed that C-reactive protein, an inflammatory marker, was significantly elevated in men with metabolic syndrome compared to those without metabolic syndrome.22
Current guidelines suggest that people are diabetic if their fasting glucose levels exceed 126 mg/dL (7.0 mmol/L). Levels over 109 mg/dL indicate a prediabetic state and levels below 109 are considered normal. While significantly improved from the previously used glucose tolerance test, these recommendations may still be too lenient. In October 2003, the American Diabetes Association further reduced the cut-off for impaired glucose tolerance from 109 to 100 mg/dL, meaning anyone with fasting glucose levels above 100 would be classified as prediabetic. More recently, the Life Extension Foundation has prescribed optimal fasting glucose levels of less than 86 mg/dL.23 This recommendation is based on clinical evidence that higher fasting levels can progressively and markedly increase cardiovascular risk.24
Lowering the bar on fasting glucose levels is a good thing, as it is estimated that up to one-half of diabetes sufferers have not been diagnosed.25 Screening for diabetes should begin at 45 years of age and should be repeated every three years in persons without risk factors and more frequently in individuals with risk factors.26
The Life Extension Foundation believes that high fasting blood levels of insulin (hyperinsulinemia) is the first indication of insulin resistance syndrome.
Fortunately, insulin resistance and type II diabetes lend themselves to a holistic approach to disease management. Lifestyle modifications can have a remarkable impact on prevention and treatment. Controlling insulin resistance—not the high blood sugar levels caused by it—is the key to success.
The Obesity Connection
With a death toll second only to smoking, obesity claims the lives of nearly 300,000 Americans each year.27 According to the American Diabetes Association, “Obesity is now reaching epidemic proportions in the US and elsewhere.” From 1991 to 2001, obesity in America increased 74% while the prevalence of diabetes increased 61%. The tripling of type II diabetes incidence over the last 30 years owes much to this surge in obesity.
A recent study by researchers at the Centers for Disease Control and Prevention investigated the links between obesity, diabetes, high blood pressure, high cholesterol, asthma, and arthritis. Compared to adults of a healthy weight, obese adults had twice the risk for high cholesterol, three times the risk for asthma, four times the risk for arthritis, and over six times the risk for hypertension.28 The strongest correlation was between obesity and diabetes: obese people exhibited over seven times the risk for diabetes compared with people of normal weight.
The good news is that up to 90% of type II diabetes cases can be prevented with simple lifestyle changes, including diet, exercise, and smoking cessation.29 The Diabetes Prevention Program, a multi-center trial involving over 3,200 people with impaired glucose tolerance, was the first large-scale study to demonstrate conclusively that weight loss can effectively delay type II diabetes. Results showed that lifestyle intervention, consisting of calorie reduction and 30 minutes a day of mild exercise, reduced risk by 58%—almost double that conferred by the oral diabetes drug metformin (Glucophage®). The results were so convincing that the study was concluded earlier than planned. The authors surmise that up to 10 million Americans can sharply lower their risk of diabetes through simple attention to diet, exercise, and lifestyle modification.30 These findings are supported by the earlier work of Dr. Roy Walford, who demonstrated that caloric restriction aggressively lowers both fasting glucose and blood insulin levels.23
Growing evidence suggests that C-reactive protein may also play a role in the development of central body obesity and the onset of type II diabetes.31 Abdominal fat is a major source of this inflammatory agent, and the increased risk of atherosclerosis and insulin resistance associated with visceral obesity may well be a consequence of enhanced C-reactive protein secretion. The surest and safest way to remedy the situation is to lose weight. Women who completed a 12-week restricted-calorie diet lost an average of 17.4 pounds and reduced their C-reactive protein levels by 26%.32
One thing is certain: people who are overweight are already in a prediabetic state and need to take corrective action before the damage is done. Unfortunately, most diagnoses occur far too late in the game.
The Value of Diet
While opinions differ as to which ratio of carbohydrates, proteins, and fats is optimal in preventing and treating diabetes, it is safe to say that carbohydrates create insulin. As more carbohydrates are consumed, more insulin is produced. Today’s obesity and diabetes epidemics reflect that too many people are asking their bodies to run on the wrong grade of fuel—refined carbohydrates. In the 1980s, Americans consumed an average of 12 pounds of sugar each year; today, US per-capita sugar consumption is an astounding 150+ pounds per year.33
Stanford’s Dr. Gerald Reaven suggests that a diet consisting of 45% carbohydrates, 40% “good” fats, and 15% protein will benefit individuals with insulin resistance. According to Reaven, only when healthy fats replace carbohydrates will insulin levels drop and clusters of symptoms associated with insulin resistance abate.34 Unfortunately, the standard diabetic diet recommended by most physicians is very high in carbohydrates, which raises blood sugar, stimulates insulin production, and almost guarantees that the diabetic will be a patient for life.
People need to pay attention not only to their total carbohydrate load, but also to the types of carbohydrates they eat. High-glycemic foods—such as white rice, white flour-based products, pasta, starchy vegetables, and many processed foods—are quickly converted to blood sugar when digested, causing insulin levels to spike. Conversely, the carbohydrates found in low-glycemic foods, such as asparagus, broccoli, cabbage, green beans, and other low-starch vegetables and fruits, are converted slowly to blood sugar and create a more gradual rise in blood insulin levels. Avoiding “white foods” is a simple recipe that can help you avoid trouble.
Fats and Fiber
While total fat intake does not appear to influence the risk of diabetes, consuming trans-saturated fats (trans fats), the hydrogenated or partially hydrogenated oils so ubiquitous in processed and fast foods, can greatly increase your risk for diabetes. A recent study showed that a minuscule 2% increase in calories from trans-fatty acids raised the risk of diabetes in women by 39%; conversely, a 5% increase in calories from polyunsaturated (good) fats reduced the risk for diabetes by 37%.35
If nothing else, simply replacing trans-fats in the diet with polyunsaturated fats will reduce the risk of diabetes dramatically. Dietary fats that are considered to be beneficial include extra virgin olive oil, fish oil, almond oil and almond butter, avocados, nuts, and seed oils such as sesame, pumpkin, sunflower, and flax.
Eating a diet rich in soluble and insoluble fiber improves insulin sensitivity and reduces circulating insulin levels. Fiber impedes gastric emptying and the passage of food through the gut, slows the breakdown of high-glycemic starchy foods, and delays glucose uptake into the blood. In a recent study reported in the New England Journal of Medicine, researchers conclude that a high-fiber diet significantly improves glycemic control, decreases insulin levels, and lowers plasma lipid concentrations in as little as six weeks.36
Exercise Is Essential
Exercise improves cardiovascular function and the body’s ability to metabolize glucose. Weight loss through exercise and diet correlates to a return to normal levels of insulin resistance and may be the single most effective approach to treating insulin resistance and reducing the risk of diabetes.37 Conditioned muscles are more responsive to insulin and blood sugar balance than non-conditioned muscles,33 possibly due to an increase in the number of insulin receptors on the muscle cell.
Physical exercise burns calories, and as energy expenditure is increased, the incidence of diabetes is found to decrease. Moreover, this protective effect appears to be most pronounced in individuals who are at greatest risk for developing the disease.38 Physically fit people also secrete less insulin. Results from the Nurses’ and Physicians’ Health Studies, conducted in the early 1990s, reveal that insulin response is more attenuated in physically fit individuals than in people who are less fit.39,40 Researchers recently demonstrated that when individuals are introduced to a regular exercise program, they experience a striking decrease in their risk of developing diabetes.41 In fact, regular exercise, when combined with weight loss, can reduce the insulin requirements of type II diabetics by up to 100%.42,43
A low-glycemic, reduced-calorie diet with healthy fats and fiber, along with regular exercise, is a safe and effective means to prevent and treat diabetes, as well as to shed excess weight.