Type 2 diabetes is a disease of insulin resistance and reduced production of insulin by the pancreas.
While either of these metabolic abnormalities can result in full-blown type 2 diabetes, in the majority of affected individuals, both are present.
Insulin resistance is a condition in which the body’s cells are insensitive or resistant to the insulin it produces.
In other words, insulin is made, but it can’t do its job moving glucose into cells or it does the job inefficiently.
The natural consequence of insulin resistance is elevated blood glucose.
The pancreas responds by putting out more insulin, which shifts the beta cells into overdrive.
Insulin resistance is generally present for many years prior to the diagnosis and is a key feature of prediabetes.
What commonly triggers the progression to type 2 diabetes is that, in addition to insulin resistance, the insulin-producing beta cells begin to fail and the amount of insulin produced declines.
This failure may well be the result of beta cell exhaustion.
By the time a person is diagnosed, insulin production has commonly diminished to about 50 percent of normal, although in some individuals insulin production remains high.
Although insulin resistance tends to remain relatively constant over time, a steady decline in insulin production generally continues if changes in diet and lifestyle are not made.
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Type 2 diabetes was once known as adult-onset diabetes or non-insulin-dependent diabetes mellitus , as it was a disease that occurred almost exclusively in adults. Although exceedingly rare prior to the twentieth century, today type 2 diabetes is a global epidemic and accounts for 90–95 percent of all diabetes. While type 2 diabetes was once unheard of in young people, it now accounts for 20–50 percent of diabetes in youth.
Although type 2 diabetes is the focus of this book, people with type 1 diabetes will find many of the dietary strategies useful for them as well.
Gestational diabetes
Gestational diabetes is a temporary condition during pregnancy that is often resolved with the birth of the infant. Its incidence has risen from 3–5 percent of pregnancies prior to the twenty-first century to 5–10 percent today.
An estimated 50 percent of women with gestational diabetes go on to develop type 2 diabetes.
HOW IS TYPE 2 DIABETES DIAGNOSED?
T ype 2 diabetes may be suspected if you experience the following common symptoms of the disease:
■ Blurred vision
■ Fatigue
■ Itchy skin
■ Pain, numbness, or pain in extremities
■ Polydipsia (constant thirst)
■ Polyphagia (increased hunger)
■ Polyuria (frequent urination)
■ Recurrent infections
■ Slow wound healing
■ Sudden, unexpected weight loss
Some people with type 2 diabetes don’t experience obvious symptoms.
In such cases, the disease could be discovered by chance at an annual checkup or because of an unrelated condition.
Long before you’re diagnosed with type 2 diabetes, prediabetes has been present for some time—often for several years.
Prediabetes—also called impaired glucose tolerance (IGT)—is a condition in which blood sugar is elevated, but not elevated enough to be classified as diabetes.
This is not a benign condition, as chronically elevated blood sugar damages the body and increases the risk of many chronic conditions.
If your doctor or health-care provider suspects diabetes or prediabetes, special tests will be ordered.
The following are the four tests most commonly used to confirm a diabetes or prediabetes diagnosis:
1. Fasting plasma glucose. After a fast of at least eight hours (nothing by mouth except water), your blood sugar is tested. Your fasting blood glucose results will determine whether or not you have diabetes or prediabetes. See the table below:
DIAGNOSIS
FASTING PLASMA GLUCOSE
Diabetes
126 mg/dL (7.0 mmol/L) or higher
Prediabetes
100–125 mg/dL (5.6 to 6.9 mmol/L)
Normal
60–99 mg/dL (3.3 to 5.5 mmol/L)
2. A1c (or HbA1c). This is a blood test that provides information about your average blood sugar levels over the past two to three months. It measures the percentage of blood sugar attached to hemoglobin (the oxygen-carrying protein in red blood cells). The result is reported as a percentage, as shown in the table below:
DIAGNOSIS
A1 c
Diabetes
6.5% or more
Prediabetes
5.7–6.4%
Normal
Less than 5.7%
3. Oral glucose tolerance test. This test measures how well your body uses sugar. You fast overnight and then drink a sugary liquid (glucose dissolved in water). Your blood sugar is then measured periodically over the next two hours. Interpretation of the results are shown in the table below:
DIAGNOSIS
ORAL GLUCOSE TOLERANCE TEST AT TWO HOURS
Diabetes
200 mg/dL (11.1 mmol/L) or higher
Prediabetes
140–199 mg/dL (7.8–11.0 mmol/L)
Normal
140 mg/dL (7.8 mmol/L) or less
4. Random plasma glucose. This is a random measure of your blood sugar level at any time during the day, irrespective of the time of your last meal. A random plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher suggests diabetes.
DEVASTATION BY DIABETES
I nsulin resistance, rising blood sugar, and diabetes come with a dreadful physiological price tag.
Living in a milieu of excess glucose, your tissues become awash in a syrupy fluid.
The sugars stick to proteins, bridging spaces between connective tissue layers.
Arteries stiffen, the lenses of the eyes become less flexible, internal wiring malfunctions, and aging accelerates.
Every body system is affected, and the consequence is a metabolic meltdown.
As a result, people with diabetes have a two- to threefold increase in risk of mortality compared with those who do not have diabetes.
The devastation wrought by diabetes is responsible for a myriad of complications.
Cardiovascular Disease
According to the American Heart Association, about 84 percent of people age sixty-five or older with diabetes die from heart disease or stroke. Adults with diabetes are two to four times more likely to die from heart disease or heart failure than adults without diabetes. This is thought to be because people with diabetes have more hypertension; higher levels of cholesterol, triglycerides, and blood glucose; increased rates of obesity; and tend to be less physically active.
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Deaths from cardiovascular disease also occur at earlier ages than they do in people who do not have diabetes.
Peripheral Artery Disease (PAD)
An estimated 10–20 percent of people with diabetes suffer from peripheral artery disease (PAD), with its incidence increasing with age. This condition is marked by narrowing of the arteries to the legs, stomach, arms, and head caused by atherosclerosis. Diabetic foot ulcers resulting from PAD are also a common complication, with 12–25 percent of people with diabetes being affected in their lifetime.
Peripheral Neuropathy
Diabetes can damage nerves and cause pain in the limbs, especially in the legs, feet, and hands. This impairs feeling and makes it easy to miss small injuries that can become infected. If left unchecked, peripheral neuropathy can lead to serious infections. Diabetes is responsible for about 60 percent of nontraumatic, lower-limb amputations among adults age twenty or older.
Kidney Disease
In 2011 and 2012, the prevalence of chronic kidney disease in American adults with diabetes was 36.5 percent, and diabetes was the main cause of kidney failure in 44 percent of new cases.
Cancer
Diabetes is positively associated with overall cancer risk, particularly cancers of the pancreas (1.94 times the risk), colon (1.38 times the risk), rectum (1.2 times the risk), liver (2.2 times the risk), and endometrium (2.1 times the risk).
In a 2018 American study, people with diabetes had a 47 percent greater chance of having colorectal cancer (CRC) than individuals without the disease. Although the increase in CRC risk was not significant in people age sixty-five or older, the odds of developing the disease in those younger than sixty-five were nearly five times greater than those without diabetes.
Cognitive Dysfunction
Vascular dementia and Alzheimer’s disease are frequently seen in diabetes sufferers. One recent meta-analysis (combined findings) of seventeen studies involving close to two million individuals reported that participants with diabetes had a 1.54 times increased risk of Alzheimer’s disease.
Other Conditions
Diabetic retinopathy, a complication of diabetes that involves damage to the retinal blood vessels, is the leading cause of blindness in American adults. It’s estimated to impact over 25 percent of Americans with type 2 diabetes.
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Also, a 2018 study of Chinese men reported that almost 65 percent of patients with diabetes suffered from erectile dysfunction (ED).
Finally, diabetes is strongly associated with the risk and severity of depression. Depression is present in about 25 percent of people with type 2 diabetes.
All in all, these complications pose a rather gloomy reality for anyone progressing down the very slippery slope of diabetes. Fortunately, all these conditions can be dramatically diminished, halted in their tracks, or even reversed with appropriate diet and lifestyle changes.
THE MAKING OF A METABOLIC MONSTER
T he hallmark of our modern type 2 diabetes epidemic is insulin resistance.
Even when adequate insulin is produced by the beta cells of the pancreas, the body cells (regardless of whether they’re in muscle, liver, or fat tissue) do not respond to the insulin as they should.
This can happen when there’s a problem with insulin receptors or a glitch in the mechanisms that work together to move glucose into cells.
Even with plenty of insulin in the bloodstream, glucose can’t get into the cells to be used for energy.
This means that sugar accumulates in the bloodstream, causing high blood sugar (hyperglycemia).
The pancreas responds to this surge in blood sugar by supplying even more insulin.
This chronic excess of insulin circulating in the bloodstream is known as hyperinsulinemia.
To be clear, insulin is an extremely important hormone in the body, helping to regulate many body systems.
However, like all hormones, there’s an optimal level of insulin that’s needed to maintain health.
When insulin in the bloodstream is persistently elevated and the body is resistant to that insulin, a metabolic mess ensues.
Chronically high insulin levels can lead to weight gain, high triglyceride and uric acid levels, arteriosclerosis (hardening of the arteries), hypertension, and endothelial dysfunction (which impairs blood flow).
However, as you may recall, Diane lost five pounds (2.3 kg) just prior to her type 2 diabetes diagnosis.
Why would she lose weight when she had high insulin levels due to insulin resistance?
In Diane’s case (and for many others with a new type 2 diabetes diagnosis), her body had become so insulin resistant that she couldn’t use the sugar from her food.
Her blood glucose soared, and she began to dump sugar in her urine.
Her body turned to its fat and muscle stores for energy, so she lost weight.
What Causes Insulin Resistance?
The vast majority of insulin resistance is a function of overweight and underactivity. While it’s true that genes can be responsible for ineffective insulin receptor sites or can adversely affect the cascade of events necessary for glucose to enter cells, excess body weight, especially visceral fat (see the box on page 9 ), is the chief culprit.
According to the International Diabetes Federation, a waist measurement of 37 inches (94 cm) or more in Caucasian men, 35.5 inches (90 cm) or more in Asian men, and 31.5 inches (80 cm) or more in women increases risk.
Underactivity contributes to being overweight and to metabolic changes that further promote insulin resistance.