Can you reverse prediabetes? What the landmark prevention trial actually showed

"Prediabetes" sounds like a milder disease. It is better understood as a warning label. MedlinePlus defines it as blood glucose levels that are higher than normal but not high enough to be called diabetes, and notes that people with prediabetes are more likely to develop type 2 diabetes, heart disease and stroke — but that lifestyle changes made now may delay or prevent type 2 diabetes [s1]. The honest answer to "can you reverse it" is that a substantial share of people can push their glucose back toward normal, that doing so lowers future risk, and that the evidence for this is unusually strong for a lifestyle claim.

Where the number comes from

Prediabetes is common. About 1 out of every 3 adults has it, and it usually arises when the body has a problem with insulin — either insulin resistance, in which cells cannot use insulin properly, or an inability to make enough insulin to keep blood sugar in a healthy range [s1]. Researchers think being overweight and not getting regular physical activity are major factors in causing it [s1]. Those two levers — weight and activity — are exactly the ones the defining trial pulled.

The trial that set the numbers

The Diabetes Prevention Program, published in the New England Journal of Medicine in 2002, randomly assigned 3,234 non-diabetic adults with elevated fasting and post-load glucose to one of three groups: placebo, metformin at 850 mg twice daily, or a lifestyle-modification programme with the goals of at least 7 percent weight loss and at least 150 minutes of physical activity per week [s2]. The participants were, on average, 51 years old with a body-mass index of 34.0; 68 percent were women and 45 percent were from minority groups [s2].

Over an average follow-up of 2.8 years, the incidence of diabetes was 11.0, 7.8 and 4.8 cases per 100 person-years in the placebo, metformin and lifestyle groups respectively [s2]. In relative terms, the lifestyle intervention reduced the incidence of diabetes by 58 percent (95 percent confidence interval, 48 to 66 percent) and metformin by 31 percent (17 to 43 percent), compared with placebo — and the lifestyle programme was significantly more effective than the drug [s2]. To prevent one case of diabetes over three years, 6.9 people would need to take part in the lifestyle programme, versus 13.9 for metformin [s2]. That is the empirical core of every "you can prevent diabetes" message: a modest, specific target — roughly 7 percent of body weight and a half-hour of activity most days — moving progression by more than half.

What "reversal" buys you

Preventing progression is one thing; actually returning glucose to the normal range is another, and a follow-up analysis asked whether that return means anything. Drawing on 1,990 participants tracked into the Diabetes Prevention Program Outcomes Study, researchers compared people who had returned to normal glucose regulation at least once with those who consistently met criteria for prediabetes [s3]. Diabetes risk over the follow-up was 56 percent lower for those who had reverted to normal glucose regulation than for those who stayed prediabetic (hazard ratio 0.44, 95 percent confidence interval 0.37 to 0.55) [s3].

The authors' framing is worth keeping. They concluded that prediabetes is a high-risk state for diabetes — especially in people who remain prediabetic despite intensive lifestyle intervention — and that reversion to normal glucose regulation, even if only transient, is associated with a significantly reduced risk of future diabetes, independent of which treatment group a person had been in [s3]. In other words, getting the number back into the normal range appears to matter in its own right, not merely as a marker of who was going to do well anyway.

What this does and doesn't mean

Two cautions belong on any reading of this. First, "reversal" here means glucose returning to a normal range and a lower risk of progression — not a cure that removes the underlying tendency, which is why continued follow-up still showed people slipping back. Second, none of these figures is a personal prescription. The 7-percent, 150-minute target was a trial protocol delivered with intensive support, not a self-help dose, and whether metformin, structured lifestyle programmes or neither is appropriate for a given person depends on their full risk profile and is a clinical decision.

What the evidence settles is the direction and the size of the effect: prediabetes is a genuine high-risk state, it is often modifiable, and the return to normal glucose is worth aiming for. If a test has put you in this range, it is a reason to talk to a clinician about a plan — and a reason for some optimism about what that plan can do.

Sources

• Prediabetes — MedlinePlus, National Library of Medicine
• Reduction in the Incidence of Type 2 Diabetes with Lifestyle Intervention or Metformin — New England Journal of Medicine, 2002-02-07
• Effect of regression from prediabetes to normal glucose regulation on long-term reduction in diabetes risk: results from the Diabetes Prevention Program Outcomes Study — The Lancet, 2012-06-01