An estimated 98 million American adults are living with prediabetes, and more than 8 in 10 do not know they have it, according to the American Diabetes Association's summary of CDC data. That silent majority is the reason clinicians keep returning to a single trial from the early 2000s.
The Diabetes Prevention Program, an NIH-funded randomized controlled trial of 3,234 adults with elevated blood sugar, reported in The New England Journal of Medicine that a structured lifestyle program cut the incidence of type 2 diabetes by 58 percent compared with placebo over an average follow-up of 2.8 years. Metformin, the standard first-line diabetes drug, reduced incidence by 31 percent in the same trial.
What the lifestyle arm actually did
The interventions were not exotic. Participants aimed for at least 7 percent weight loss and at least 150 minutes of moderate physical activity per week, such as brisk walking, as described by the National Institute of Diabetes and Digestive and Kidney Diseases. The trial ran across 27 US clinical centers, with a mean participant age of 51 and a mean body mass index of 34.
The result was durable but not permanent. In the long-term follow-up known as the Diabetes Prevention Program Outcomes Study, the lifestyle group still showed a 27 percent delay in diabetes onset at 15 years, and metformin an 18 percent delay. Most participants eventually developed diabetes, which is a useful reminder that "reversal" of prediabetes is a moving target rather than a one-time cure.
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The 150-minute target on its own
More recent work has probed how much of the benefit comes from exercise alone. A 2025 review in Diabetes Care revisited the DPP and its outcomes study and confirmed that the combination of modest weight loss and 150 minutes of weekly activity remains the most reliably replicated lifestyle package in diabetes prevention.
Diet plays a supporting role. The DPP curriculum emphasized cutting saturated fat and refined carbohydrates and increasing fiber, an approach still reflected in most current prevention guidance. None of this requires a specialty diet or a gym membership. Brisk walking, spread across the week, meets the activity target for most people.
What this means if your fasting glucose is creeping up
Prediabetes is defined by blood sugar levels above normal but below the diagnostic cutoff for type 2 diabetes, and it usually produces no symptoms. Because it is a lab finding rather than a felt illness, screening matters. Anyone with a family history, a BMI in the overweight range, or a prior gestational diabetes diagnosis should talk with their doctor about testing and, if the numbers warrant it, about enrolling in a CDC-recognized lifestyle change program.
The DPP evidence is unusually strong for a lifestyle intervention, but it is not a promise. Weight regain, injury, or a return to old eating patterns can push blood sugar back up. The trial's honest message is that the risk of progressing to diabetes can be roughly halved with sustained, ordinary effort, and that the effort has to keep going.
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