| 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
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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.
Lifestyle Considerations
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
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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.
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