Taking a new approach to type 2 diabetes
From the May ACP-ASIM Observer, copyright © 2002 by the American College of Physicians-American Society of Internal Medicine.
By Margie Patlak
As type 2 diabetes in this country takes on epidemic proportions, experts are urging primary care physicians to take a new approach to the disease. Instead of simply treating diabetes and its comorbidities, they say, physicians must help patients avoid getting the disease and its life-shortening complications.
The statistics on type 2 diabetes are staggering. In this country, the number of diabetics has tripled in the last 30 years, and the disease now affects one in five people over age 65.
Even more disturbing, type 2 diabetes is appearing more frequently in younger people; even children are starting to succumb to what is commonly called adult-onset diabetes. Experts say these developments are particularly sobering because the longer patients have the disorder, the more likely they are to develop complications.
While the growing prevalence of type 2 diabetes is disheartening, there is good news from the research front. New studies suggest that a few simple tests can help you detect diabetes-prone patients, and basic lifestyle changes can keep the disease and its complications at bay.
"It is not inevitable that people at high risk for diabetes will develop the disease," said endocrinologist David Nathan, MD, of Harvard University and Massachusetts General Hospital.
The long view
The emerging view of diabetes sees the disease as the end stage of a progressive disorder that disrupts more than blood sugar levels for years before physicians ever diagnose it.
"Diabetes doesn't just spring forth," Dr. Nathan said. "People develop diabetes over a number of years, along with several metabolic abnormalities that are also cardiovascular disease risk factors. That might explain why patients are at such high risk for heart disease once they develop diabetes. The risk factors have been there for years."
While the end stage of type 2 diabetes is characterized by a lack of insulin, it is preceded by years of insulin resistance. The pancreas battles that resistance by secreting more insulin, but its capacity to produce insulin gradually declines. When the pancreas cannot meet the body's needs, diabetes ensues.
Experts now think insulin resistance and the subsequent flooding of tissues with excessive amounts of insulin foster several abnormalities that can be easily detected in an office visit. Telltale signs include high blood levels of triglycerides, low blood levels of high density lipoprotein (HDL) cholesterol, hypertension and rising fasting or post-prandial blood sugar levels that eventually surpass the cutoff for a diabetes diagnosis.
This constellation of abnormalities preceding diabetes was originally identified in 1988 by Stanford University endocrinologist Gerald Reaven, MD. Since then, abdominal obesity has been added to the list, and four years ago the World Health Organization formally recognized the entire group of bodily malfunctions as "metabolic syndrome."
A recent study done by CDC researchers found that up to one in four Americans has metabolic syndrome. Experts find that figure disturbing because 5% to 10% of patients with metabolic syndrome develop diabetes every year.
Detecting the diabetes-prone
Some argue that metabolic syndrome is not a true disorder with a single underlying cause, but merely a constellation of risk factors. Few, however, doubt the value of metabolic syndrome as a red flag for impending diabetes. Dr. Reaven goes so far as to say that detecting any form of insulin resistance "is a better predictor of diabetes risk than family history."
Diagnosing insulin resistance can be tricky, however, because patients rarely have all—or even most—metabolic syndrome factors. Researchers think that some signs, however, are more critical than others.
For example, Dr. Reaven has found that a combination of high triglycerides and low HDL cholesterol is one of the earliest indicators of insulin resistance. He said that this combination also reliably predicts whether patients will develop diabetes.
Abdominal obesity is a telltale sign of metabolic syndrome, which researchers say precedes type 2 diabetes.
Others, however, argue that abdominal obesity is the most important component of metabolic syndrome and a better predictor of impending diabetes. (See "Fat: culprit or accomplice in type 2 diabetes?")
Experts agree that impaired glucose tolerance is the most reliable indicator for "prediabetes," a condition that on the disease continuum is closest to full-fledged diabetes. Impaired glucose tolerance can be present even when patients have normal fasting blood sugar levels. Doctors can expect at least half of patients with impaired glucose tolerance to develop diabetes within 10 years.
Physicians on managed care panels often find that patients' insurers don't cover glucose tolerance tests. Others are hesitant to ask patients to undergo the inconvenience of such testing. If you opt not to run a two-hour post-prandial blood glucose test, high fasting blood sugar levels—so-called impaired fasting glucose—are the next best indicator of prediabetes.
Pinpointing patients at high risk for diabetes is only half the battle. You must also convince them to improve their diet and increase exercise to keep diabetes at bay.
While the thought of counseling patients about diet and exercise may make you cringe, experts point out that patients don't have to shed much weight or do demanding exercise routines to dramatically cut their diabetes risk.
Consider the results of the NIH's large Diabetes Prevention Program clinical trial, which were published in the Feb. 7, 2002, New England Journal of Medicine. By losing just 7% of their body weight and walking a half-hour a day five times a week, volunteers with impaired glucose intolerance were able within three years to cut their risk of developing diabetes in half, compared to the control group.
Volunteers in the study took classes covering diet, exercise and behavior modification. They then received monthly follow-up counseling to reinforce behavioral changes.
"We didn't have to get people down to their ideal body weight or give them unrealistic expectations," said Dr. Nathan, who was one of the trial's principal investigators. "They lost 15 pounds, not 100."
Yale University endocrinologist Reza Yavari, MD, said he provides intensive education and counseling to people with metabolic syndrome or diabetes at his private clinic. "You need to educate patients," he explained, "because they could exercise for two hours but immediately ingest 1,000 calories afterward because they don't realize how many calories are in a Snickers bar."
Melvyn L. Sterling, FACP, a general internist in Orange, Calif., and the Governor for the Southern California Region II Chapter, said he gets better results when patients see a dietician or enroll in a weight-loss program such as Weight Watchers. To push them in that direction, he talks to patients about the dangers of diabetes and its complications.
"Different people have different buttons you need to push," Dr. Sterling explained. "To inspire men, I point out that diabetic neuropathy may deprive them of their sexual potency."
Dr. Yavari emphasized that you need to understand patients' lifestyles and reasons for not eating a good diet. "Are they moms who eat their kids' leftovers, or sales reps on the road who eat a lot of fast food?" he asked. "You need to understand where their source of calories is coming from, then provide alternatives."
For stress eaters, Dr. Yavari continued, "Try to find the main stressor that causes their overeating and suggest ways to deal with it. These little steps can make a huge impact on patients' lives."
You also need to be realistic when advising patients about exercise. "Don't tell someone who weighs 250 pounds to get on a treadmill," Dr. Yavari explained. "Because they are deconditioned, they won't burn enough calories to meet their weight loss goals, plus they'll hate it."
He often eases obese patients into fitness regimens by starting them out with yoga. "Studies show that you need steady—not heavy-duty—exercise to control diabetes," Dr. Yavari said. "Exercise has to be regular and enjoyable."
An even bigger challenge can be convincing diabetes-prone patients to eat foods that won't increase their cardiovascular disease risk and aggravate their excessive secretion of insulin.
"Everybody's screaming about low-fat diets," said Stanford's Dr. Reaven. "But there's nothing more depressing than seeing an insulin-resistant Silicon Valley executive who eats hardly any fat but keeps watching his triglycerides go up. That's because he's substituting carbohydrates for fat. If you are insulin-resistant, the more carbohydrates you eat, the more your insulin and triglycerides go up, and your HDL goes down."
Dr. Reaven said studies show a diet high in unsaturated fat doesn't increase insulin levels and is just as good as a diet high in carbohydrates for lowering LDL cholesterol. Recent research also finds that diets that don't prompt weight gain but are high in polyunsaturated fat are linked to a lower risk of diabetes.
Dr. Yavari cautioned, however, that some studies indicate that a diet high in polyunsaturated fats other than omega-3 fatty acids may boost the inflammatory response in the cardiovascular wall, as well as triglyceride production. Both Drs. Reaven and Yavari agreed that a diet high in monounsaturated fats, such as olive oil, might be a better alternative.
Recent studies also find that people can cut their risk of diabetes by eating diets high in fiber, fruits and vegetables, whole grains, fish and poultry. By contrast, a diabetes-boosting diet is laden with refined grains, sweets and desserts, red meats, fried foods and high-fat dairy products.
When efforts to modify diabetes-prone patients' weight, diet or exercise patterns fail, several drugs can help prevent diabetes. Diabetes Prevention Program researchers, for example, found that patients with impaired glucose tolerance who took metformin had about one-third the risk of developing diabetes as the control group.
"Metformin is well tolerated," noted Dr. Sterling, "so if I have a patient with prediabetes, it's my drug of choice. But if the patient can't tolerate it, I might try thiazolidinediones like Actos or Avandia." (Although the FDA has approved all three drugs to treat diabetes, it has not approved any of them to treat patients on the verge of the disorder.)
Dr. Sterling said that when all else fails, he also prescribes weight-loss drugs such as orlistat for overweight, diabetes-prone patients. "They're expensive and have side effects," he said, "so they are not my first choice." For compulsive eaters, he prescribes antidepressants shown to be effective at curbing that compulsion. (For more on weight-loss drugs, see "The role of treating drugs in obesity" online.)
Dr. Yavari noted, however, that "drug treatment to prevent diabetes without lifestyle interventions is like a Band-Aid on a huge gushing wound." He added that Dr. Nathan's research found that metformin was only half as effective at lowering diabetes risk as lifestyle modification efforts.
Whatever tactic you use, experts say you need to do something now to help prevent patients from developing diabetes. Otherwise, Dr. Yavari said, "We're really going to regret it in 10 to 15 years when it's estimated that one out of four Americans will have the disease."
Margie Patlak is a freelance science writer in Elkins Park, Pa.
The information included herein should never be used as a substitute for clinical judgment and does not represent an official position of ACP-ASIM.
Recognizing the links between excess weight and diabetes, researchers have coined a new term to describe the condition: "diabesity."
In part because more than 75% of diabetics are obese, some researchers think that excess body fat triggers the insulin resistance that fosters type 2 diabetes. This view stems from the growing awareness that fat tissue is one of the body's largest endocrine organs. Fat cells secrete a wealth of hormones and cytokines that substantially affect other tissues.
Not all fat deposits are the same. "Visceral fat is a different animal than types of fat found elsewhere in the body," noted Yale University endocrinologist Reza Yavari, MD. Unlike subcutaneous fat, visceral fat secretes far more hormones and other circulating substances that counter the effects of insulin at the cellular level. In addition, free fatty acids readily released by abdominal fat hamper the action of insulin in muscle cells.
"There are a lot of data—demographic, pathophysiologic and molecular—that suggest visceral fat is the main culprit behind metabolic syndrome and type 2 diabetes," Dr. Yavari explained. Losing small amounts of weight can effectively prevent diabetes, he said, because patients tend to lose abdominal fat first.
But Stanford University endocrinologist Gerald Reaven, MD, views fat as more of an accomplice than an instigator of diabetes. He pointed out that not all obese people become diabetic, and that many obese people are highly insulin sensitive. Substantial numbers of slim people also get the disease.
Dr. Reaven's studies indicate that one-quarter of patient's insulin resistance can be attributed to how much excess fat they carry on their bodies, while another quarter stems from a lack of physical activity. In his view, patients' genetic makeup accounts for the bulk of their insulin resistance. As evidence, he pointed out that certain ethnic groups such as Hispanics, Asians, African Americans and Native Americans are all exceptionally prone to type 2 diabetes.
Regardless of fat's relationship to diabetes, most experts agree that excess weight and a sedentary lifestyle certainly increase the odds for patients with a genetic tendency toward insulin resistance.
"A 10-pound weight gain in someone who is insulin sensitive may have no effect at all, but a major effect in someone who is insulin resistant and borderline diabetic," Dr. Reaven said. That's why he recommends that overweight, insulin-resistant patients shed some pounds.
Dr. Yavari said he takes things a bit further. Because of the role he thinks visceral fat plays in fueling diabetes, he urges high-risk patients to lose abdominal fat even before they are technically labeled overweight.
"If you have a patient who is hitting midlife and starting to put on weight around the belly," Dr. Yavari said, "it's time to advise her to start working out and lose some weight. Don't wait until she's 50 pounds overweight and already has diabetes."
Researchers think that metabolic syndrome, also known as dysmetabolic syndrome X, is a red flag that a patient may develop diabetes. While the major criterion is insulin resistance denoted by hyperinsulinemia relative to glucose levels, you should look for other signs. The following list of criteria was created by the American Association of Clinical Endocrinologists to create a new ICD-9-CM code, 277.7, and was approved by the CDC.
- Acanthosis nigricans
- Waist circumference >102 cm for men and >88 cm for women
- Dyslipidemia (HDL cholesterol < 45 mg/dl for women, and < 35 mg/dl for men, or triglycerides >150 mg/dl)
- Impaired fasting glucose or type 2 diabetes
- Polycystic ovary syndrome
- Vascular endothelial dysfunction
- Coronary heart disease
The College has recently created a brochure to help alert patients to risk factors and symptoms of type 2 diabetes.
The new brochure encourages patients to talk to their internist if they are experiencing any of the symptoms. It also discusses the link between diabetes, heart disease and high blood pressure.
You can download a copy of the brochure, along with other materials from the College's Doctors for Adults educational campaign, at www.doctorsforadults.com. Packages of 100 brochures are also available for $20.
To order, call ACP-ASIM Customer Service at 800-523-1546, ext. 2600 or 215-351-2600 (9 a.m. to 5 p.m., EDT). Ask for product code 700100120.
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