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What is prediabetes and why does it matter?

Posted By Monique Tello, MD, MPH On January 25, 2017 @ 9:30 am In Diabetes,Diet and Weight Loss,Exercise and Fitness,Healthy Aging,Prevention | Comments Disabled

When I’m seeing a new patient, I am especially alert to certain pieces of their history. Do they have a strong family history of diabetes? Are they of Latino, Asian, Native-American, or African-American ethnicity? Did they have diabetes in pregnancy? Are they overweight or obese? Do they have polycystic ovarian syndrome (PCOS)?

Why do I care about these things? Because they may be clues that the patient is at risk for developing adult-onset (type 2) diabetes, and that can lead to multiple major medical problems.

Many people have heard of type 2 diabetes, a disease where the body loses its ability to manage sugar levels. Adult-onset diabetes most often affects people with known risk factors and can take years to fully develop, unlike juvenile (type 1) diabetes, which can develop randomly and quickly.

Here is why high blood sugar is a problem

Untreated or undertreated diabetes means persistently high blood sugars, which can cause horrible arterial blockages, resulting in strokes and heart attacks. High blood sugars also cause nerve damage, with burning leg pain that eventually gives way to numbness. This, combined with the arterial blockages, can result in deformities and dead tissue, which is why many people with diabetes end up with amputations. The tiny blood vessels to the retina are also affected, which can cause blindness. And don’t forget the kidneys, which are especially susceptible to the damage caused by high blood sugar. Diabetes is a leading cause of kidney failure requiring dialysis and/or kidney transplant. But wait! There’s more. High blood sugar impairs the white blood cell function critical to a healthy immune system, and sugar is a great source of energy for invading bacteria and fungi. These factors put folks at risk of nasty infections of all kinds.

These facts scare me. Not just because I’m the doctor who gets to help manage these not-fun issues, but because I’m of Latina descent and diabetes runs in my own family. I’m at risk too.

So, what can we do? If we know who is at risk for diabetes, and it takes years to develop, we should be able to prevent it, right? Right!

Keeping prediabetes from becoming diabetes

A recent in-depth article by endocrine experts declares prediabetes a worldwide epidemic (which it is).1 Prediabetes is defined by fasting blood sugars between 100 and 125, or an abnormal result on an oral glucose tolerance test. What can we do to treat prediabetes? The authors reviewed multiple large, well-conducted studies, and all showed that prediabetes can be targeted and diabetes delayed or prevented.

One of the largest studies was conducted here in the U.S.2 Over 3,000 people from 27 centers who were overweight or obese and had prediabetes were randomly assigned to one of three groups:

  1. standard lifestyle recommendations plus the medication metformin (Glucophage);
  2. standard lifestyle recommendations plus a placebo pill;
  3. an intensive program of lifestyle modification.

The intensive program included individualized dietary counseling, as well as instruction to walk briskly or do other exercise for 120 minutes per week, with the goal of some modest weight loss.

Investigators followed the subjects over three years, and the results were consistent with those from many other studies: the people in the intensive lifestyle modification group (nutrition counseling and exercise guidance) were far less likely to develop diabetes in that time span than those in either of the other groups.3,4,5 Want numbers? The estimated cumulative incidence of diabetes at three years was 30% for placebo, 22% for metformin, and 14% for lifestyle modification. The incidence of diabetes was 39% lower in the lifestyle modification group than in the metformin group. As a matter of fact, they shut down the study early because it was deemed unethical to keep the subjects in the placebo and metformin-only groups from proper treatment.

The authors of the prediabetes review also looked at the multitude of other studies that more closely examined what kinds of diets are useful and concluded that “The consensus is that a diet rich in whole grains, vegetables, fruit, monounsaturated fat, and low in animal fat, trans fats, and simple sugars is beneficial, along with maintenance of ideal body weight and an active lifestyle.”

It’s really just common sense. And that’s why my husband and I greatly limit our intake of sugar and carbs, get four-plus servings of plant-based foods daily, and exercise.

A word about medication

For my patients who for whatever reason cannot change their diet and lifestyle, I do recommend a medication. For patients who are on the cusp of diabetes and who have multiple risk factors or other diseases, medication really is indicated. There are also people who want to add a medication to diet and exercise in order to boost weight loss and further decrease their risk, and that’s fair as well.

I know that using medications for prediabetes is controversial. Other doctors have warned that the label “pre-diabetes” is over-inclusive and that it’s all a vast big-pharma marketing scam.6 It’s true that we have to be informed about what we’re prescribing and why. But based on what I’ve seen in my career, I definitely do NOT want to develop diabetes myself, and if you’re at risk, believe me, you don’t either. So, consider the pros and cons of everything, talk to your doctor, and decide for yourself what action you want to take. And then, take action.


  1. Edwards CM, Cusi K. Prediabetes: A Worldwide Epidemic. Endocrinology and Metabolism Clinics of North America, December 2016.
  2. Knowler WC, Barrett-Connor E, Fowler SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine, February 7, 2002.
  3. Pan XR, Li GW, Hu YH, et al. Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance. The Da Qing IGT and Diabetes Study. Diabetes Care, April 1997.
  4. Tuomilehto J, Lindstrom J, Eriksson JG, et al. Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. New England Journal of Medicine, May 3, 2001.
  5. Lindstrom J, Peltonen M, Eriksson JG, et al. Improved lifestyle and decreased diabetes risk over 13 years: long-term follow-up of the randomised Finnish Diabetes Prevention Study (DPS). Diabetologia, February 2013.
  6. Prediabetes: can prevention come too soon? Blog post by Richard Lehman, Cochrane UK Senior Fellow in General Practice, November 11, 2016.

Related Information: Starting to Exercise

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