Prediabetes is a warning sign that an individual is at an increased risk of developing type 2 diabetes. If it goes unmanaged, prediabetes can lead to long-term damage, including to the heart and blood vessels. But is there any way it can be reversed? And can this be achieved by changes in diet and exercise?

Diabetes — specifically type 2 diabetes— is becoming one of the most challenging health problems of the 21st century. By 2025, 380 million people worldwide are also expected to be diagnosed with diabetes.

As diabetes is a risk factor for many other diseases and chronic health conditions — cardiovascular disease, renal disease, stroke, and blindness to name a few — its management and treatment is ever more crucial.

However, before people go on to develop type 2 diabetes, many people are considered in a precursor stage called prediabetes. This is a health condition in which people experience higher than healthy blood sugar levels — but not so much that it can be diagnosed as type 2 diabetes. Nevertheless, having prediabetes is a major risk factor for type 2 diabetes.

When it comes to scaling this problem, looking at the statistics of people with prediabetes paints a clear picture: over one in three people in the U.S. and the U.K. are diagnosed with prediabetes.

So, if prediabetes is seen as an early warning sign for type 2 diabetes, is there nothing people can do to correct their course? Could serious lifestyle changes not reverse this condition?

These questions and more were the topic of discussion for our May podcast “In Conversation: Can diet and exercise help reverse prediabetes?” Joining Dr. Hilary Guite and me this month were Dr. Thomas Barber, associate clinical professor at Warwick Medical School and consultant endocrinologist at University Hospitals Coventry and Warwickshire, and Healthline Media and Medical News Today Managing Editor Angela Chao, who shared her story about how she reversed her prediabetes diagnosis and the lifestyle changes she made to sustain it.

You can listen to this month’s episode below or on your preferred streaming platform:

In Angela’s case, not many medical professionals would have considered her blood sugar readings as indicative of something to worry about.

She doesn’t fit the typical profile of a person with prediabetes or at risk of developing diabetes — slim, young, and active. However, she said she had a rather sedentary lifestyle at the time.

“[My readings were] so low on the spectrum, I don’t even think my primary doctor at the time even had a conversation about this with me, other than just giving me the range and the diagnosis,” she said.

However, she added that after changes in the threshold for readings to be considered prediabetes, some physicians and her doctor friends appeared concerned.

Receiving a prediabetes diagnosis

“From my perspective, when I got the diagnosis, it was definitely kind of a wake-up call. ‘You need to increase your exercise level; you need to [make] some changes to your lifestyle to get back to a healthy range’ whether the threshold has changed [or not].”
— Angela Chao

Diabetes and prediabetes used to be diagnosed based on fasting glucose readings, or a standard glucose tolerance test, said Dr. Barber. This test involved ingesting 75 grams of a sugary drink and then measuring blood sugar levels over the next two hours.

The definition of prediabetes is also an ever-evolving one, and it may differ from country to country.

“Different societies and esteemed groups have different definitions. And I think the first point to make really is that whether we’re talking about diabetes or prediabetes is that we’re talking about a continuum,” said Dr. Barber.

If we take the U.S. and the U.K. as examples, we can see differences in the units of measurement and the thresholds used to diagnose prediabetes.

“[It] is a bit confusing because as you say, there are different units. But essentially, in the U.K., we use millimoles per liter for glucose, and in the U.S., it’s milligrams per deciliter. Millimoles per mole is what we tend to use clinically now and have done for some years,” said Dr. Barber.

“I think to add to the confusion, there’s also the hemoglobin A1C, which also has two separate units in terms of percentage, which is what we always traditionally used and now which has been superseded by millimoles per mole,” he continued.

Dr. Barber said that glucose is not a discrete measure but a continuous variable.

“[W]e can all kind of agree on what’s normal, agree on what’s elevated, but everything in between, there’s kind of differences of opinion,” he explained.

A few years back, the World Health Organization endorsed the usage of hemoglobin A1C to diagnose diabetes. In current clinical practice, Dr. Barber said medical professionals do rely primarily on A1C but that additional glucose readings can be helpful.

“In terms of prediabetes [in the U.K.], this is based on an A1C between 39 to 47 mmol per mol, and 39 is equivalent to an A1C of 5.7%,” he said.

“In terms of hemoglobin A1C levels, anything above a level of 48 millimoles per mole, which is equivalent to 6.5%, A1C, that is—by definition—diabetes. [I]deally, we should have at least two of those readings, which are elevated, to diagnose type 2 diabetes,” he said.

Angela said that 5.7 and above was considered prediabetes when she was diagnosed, and her A1C level was 5.8%.

Dr. Barber reminded us that diagnostic thresholds for diabetes have gradually gone down in recent years and that Angela’s readings would not have been considered prediabetes in the U.K. at the time, as the values were “not quite under cut-off but very close to normal.”

Prediabetes usually does not present with symptoms. However, in some cases, people may experience frequent thirst, get up at night to pee, experience sugar spikes, or crashes in energy levels.

“Many people who are diagnosed with prediabetes may have had it for a long time, months, possibly even years; it’s often asymptomatic. And unless people are actually tested for it, it can very easily go unnoticed,” said Dr. Barber.

Angela recounted her own experience:

“I definitely didn’t have a wide range of symptoms. However, frequently, drinking water was definitely something that I was already doing. So it was hard for me to tell if it was anything that was changing.”

However, something that she did notice before the diagnosis was low blood sugar levels, especially if she didn’t eat for extended periods.

“[T]hat was something that was very prevailing throughout the years where my blood sugar levels would fluctuate quite a bit, and I can definitely physically feel it,” she said.

However, she can now fast without trouble for over 16 hours thanks to some lifestyle changes.

Sugar spikes and crashes could be seen as early warning signs for diabetes.

“Well, prediabetes is an umbrella term, and it can either include elevated fasting glucose and/or elevated postprandial glucose,” said Dr. Barber.

Within the context of insulin resistance, Dr. Barber said it was not uncommon to experience some swings in glycemia or the concentration of sugar in the blood.

“Because the beta cells can’t produce enough insulin, for example, or the insulin is not as effective after a meal, then the outcome of that is the glucose levels tend to rise a bit higher than they should,” he explained.

“I guess the difference really is that most of the time, in the context of prediabetes, we’re not aware of this because most patients, in fact, do not …. monitor their blood glucose,” he said, adding that without close monitoring of blood sugar throughout the day, people may not physically notice these changes.

“[I]t’s entirely predictable that with improved lifestyle, weight loss, and reversing prediabetes, that you would find that glucose levels become more stable. Because the insulin becomes more effective, it’s able to deal with the swings in glycemia better,” he said, referring to Angela’s description of the changes she noticed.

Being overweight or having a high BMI, or having obesity are some of the most well-known risk factors for developing type 2 diabetes.

“Also age — the older we get, the more at risk we become. And the reason for that is that, as we age, insulin becomes slightly less effective, and its receptors and the beta cells can not function quite as well. So, the risk of developing prediabetes and diabetes increases as we get older,” said Dr. Barber.

Dr. Barber also said that stress and having a diet high in high glycemic foods and sugary drinks can also increase risk. While on the other hand, he said that having a diet rich in fiber and low in simple carbohydrates can prevent the onset of dysglycemia.

“[If] you’re sedentary and you sit or lie most of the day, and particularly watching TV—which is, I think, the worst activity in terms of sedentariness— that can impact on risk. [B]eing sedentary can worsen the risk of insulin resistance, which is a risk factor for prediabetes and type 2 diabetes.”
— Dr. Thomas Barber

Other factors to take into account are ethnic origin and genetics.

Dr. Barber detailed their findings from a recent study they conducted in the U.K. in which they found that people of South Asian ethnicity had the same risk of diabetes at a BMI of 23.9 as the white population had at 30.

Whereas in Angela’s case, it was family history that upped her risk.

“[E]ver since I was a teenager because my mother is a retired medical doctor, she had always warned me because my father’s side has a little bit of a family history with type 2 diabetes— and we’re talking about all slim people, no weight issues,” she said.

Dr. Barber said that diabetes is often touted as a result of lifestyle choices but that many forget that it is a genetic condition. He said that when there’s a strong family history, patients will not necessarily fit the classic phenotype of type 2 diabetes — having obesity, being middle-aged, male, and having a large abdomen.

“[That’s] the notion that we all kind of have in our heads of a typical person who has type 2 diabetes. And as you say, Angela doesn’t fit into any of those preconceived ideas of what that looks like,” he said.

Dr. Barber also stressed that even without those factors, being born with a genetic predisposition to diabetes can mean that people develop dysglycemia.

“[There’s] been over 40 genes, gene mutations identified, which can put you at risk of type 2 diabetes. And although that each individual effect is relatively subtle, when you combine them all together, it can lead to a cumulative effect,” he said.

The way Angela achieved the target of reversing her diabetes was through a multipronged approach: “a combination of intermittent fasting, a balanced diet with an increased amount of lower-glycemic index foods and complex carbs, and a significantly increased physical activity.”

She said she also worked with a personal trainer on doing weight and resistance training and did not do drastic changes to her diet.

“No keto, any strict dieting or short-term drastic changes that aren’t sustainable,” she said.

Dr. Barber said this strategy clearly worked for Angela but acknowledged that not many people might be able to implement such intensive changes into their lives and find it rather difficult.

“We know that intensive lifestyle treatments [w]ith focus on diet, physical activity, weight loss, and so on, can really help in preventing, or at least delaying the onset of type two diabetes,” said Dr. Barber.

“I think, at the very least, it’s a kind of early warning signal, which alerts people to the need for a change in lifestyle. And if it encourages or motivates people to change [their] lifestyle, then that has to be a good thing,” he said.

With an already low BMI, losing weight would not have been a healthy strategy for Angela.

“When I was diagnosed, I could not afford to lose weight; it was more of a sedentary lifestyle behavior [issue]. I definitely was not regularly exercising. I was working [in] very high stress, high demanding journalism jobs, breaking news, a lot of field [reporting], traveling, covering disasters—you name it,” she recalled.

Increasing muscle mass via strength training can help with insulin resistance and improve insulin sensitivity.

Dr. Barber said that the act of exercising and the release of myokines from muscles could mediate cardiometabolic benefits.

“Having a greater muscle mass can actually improve your overall metabolic rate and thereby help to maintain body weight. When you’re exercising, you’re oxidizing fat, you’re burning fat tissue, you’re using that in your muscles, and that will all help as well,” he added.

Studies have shown that regular physical activity—and not only the high intensity kind—can help stabilize blood sugar and improve its management.

“[W]hen we talk about exercise, most people think about going on a treadmill and doing a 5k run, [g]etting in a sweat, which you know, is good exercise, but actually the message should be avoidance of sedentariness,” said Dr. Barber.

“[W]e know that when you’re standing, you burn more calories; it’s better for health. If you’re walking around, that’s even better,” he said.

“And there’s been some fascinating studies [that] have looked at changing sedentary behavior, like getting up every hour or every half an hour and just walking around for a couple of minutes and doing squats in the corner of the room. They showed that just that activity during the course of the day can have transformative effects on glucose levels,” he elaborated.

What being active really means

“[Y]ou don’t have to climb Mount Everest, you don’t have to even go on the treadmill. You just need to get up every now and then walk around. And now that in itself will have a huge positive impact on your metabolic health.”
— Dr. Thomas Barber