Prediabetes: A window of opportunity

Diabetes gets a lot of attention these days, and for good reason: it can lead to serious health complications such as heart attack, kidney failure, amputation, blindness, and early death. But its precursor, aptly named prediabetes, doesn't get nearly as much airtime, despite affecting three times as many people.

One in three American adults — an estimated 96 million people — has prediabetes, which is characterized by blood sugar levels that are higher than the normal range but don't quite reach diabetes status. But the vast majority of people don't know when they have it. And this is where the danger — and opportunity — lie, Harvard experts say.

 "As with every chronic, prevalent disease, it's incredibly important to understand who's at particularly high risk of progressing from prediabetes to diabetes," says Dr. Giulio Romeo, associate medical director of the Adult Diabetes Section at Harvard-affiliated Joslin Diabetes Center.

Unlike diabetes, prediabetes is "largely silent" and typically doesn't produce blatant symptoms that might clue us in to its presence, Dr. Romeo says. But subtler signs often show up that shouldn't be ignored, offering a valuable window to curb blood sugar levels and halt progression.

"Anyone whose blood sugar falls into the prediabetes range is going in only one direction unless changes are made," says Emma Samuels Grinblatas, a registered dietitian and practice manager in the Comprehensive Weight Management Center at Harvard-affiliated Beth Israel Deaconess Medical Center. "Genetic and lifestyle factors both play a role in the development of diabetes. Whether we like it or not, our bodies will behave in certain ways. We don't get to play with our genes, but we do get to make changes in our eating behaviors and lifestyle choices."

Risk factors and clues

The same factors that play into diabetes development — overweight or obesity, inactivity, and family history — increase the risk of prediabetes. Paying attention to these, along with any persistent fatigue, should alert you that you may be in jeopardy, Dr. Romeo says.

Also notice if you're getting more infections—especially vaginal yeast infections. This can happen in women with prediabetes whose blood sugar spikes after meals — perhaps several times a day — but whose fasting glucose levels stay within normal limits (see "Three types of blood sugar tests"). "Their response to meals can't be categorized as normal," Dr. Romeo says.

After eating larger meals, some people with prediabetes also experience repeated urination or blurry vision. These signs, too, are related to temporarily surging blood sugar levels. They also happen to mirror full-blown diabetes symptoms, but on a smaller scale.

"While we like to classify things in buckets, the truth is that prediabetes and type 2 diabetes are often on a continuum — it's the same process across different stages," Dr. Romeo says. "Sometimes people are on the brink, so they notice certain signs even if they don't, by the book, have type 2 diabetes."

Frequent movement crucial

Lifestyle changes are the cornerstone of measures to prevent prediabetes from progressing, Harvard experts say. A new study, published online Sept. 21, 2022, by BMJ, underscores this concept, suggesting that women who've had a temporary form of diabetes during pregnancy can lower their risk of later developing the disease by 90% by adhering to five key lifestyle factors: healthy weight, high-quality diet, regular physical activity, moderate alcohol consumption, and not smoking. The researchers based their conclusions on an analysis of 28 years of health and lifestyle data on 4,275 women who'd had pregnancy-related diabetes; of these, 924 later developed diabetes.

Frequent movement, in particular, is pivotal in staving off the problem. A new study published online Dec. 2, 2022, by The Journal of Clinical Endocrinology and Metabolism suggests that women who take more steps each day may have a lower risk of developing diabetes. Researchers analyzed diabetes rates along with data from wearable fitness devices from 5,677 people (75% women). Participants whose daily step counts averaged 10,700 at the study's start were 44% less likely to develop diabetes over the following four years compared with those who averaged only 6,000 steps per day.

"Regular exercise plays a profound role on blood sugar," Grinblatas says. "The recommendation of 30 minutes of exercise at least five days a week can be broken down into 10-minute increments and include things like walking, yard work, and dancing. Any form of exercise is good for our bodies and brains."

And exercise pays off well beyond a shrinking waistline for people at risk of diabetes. "Exercise alone often won't result in weight loss," Dr. Romeo says, "but it has significant benefits that can't be measured by the scale — not just in terms of preventing progression to diabetes, but on your heart, mood, and many aspects of overall health not captured by a change in your weight."

Along with lifestyle changes, the drug metformin can boost diabetes prevention efforts for some people with obesity. Metformin lowers blood sugar levels by improving the way the body shuttles sugar from the blood into the cells of muscles and other tissues, where it's used as fuel. Research shows metformin reduces the odds prediabetes will progress to diabetes by about one-third, Dr. Romeo says, though lifestyle interventions work even better — lowering the chance of progression by about 60%.

"For some, maybe the focus is not about losing weight, but how you should exercise at whatever level you can — looking at this not as a sprint but as something you can incorporate into your routine over the years," he says.

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