Borderline diabetes, clinically called prediabetes, is reversible. Your A1C sits between 5.7% and 6.4%, meaning your blood sugar is elevated but hasn’t crossed into type 2 diabetes territory. The landmark Diabetes Prevention Program trial, published in the New England Journal of Medicine, found that people with prediabetes who lost 7% of their body weight and walked briskly for 150 minutes per week cut their risk of developing type 2 diabetes by 58%. That’s more effective than medication. Here’s how to put that into practice.
How Much Weight Loss Actually Matters
The 7% threshold is the target backed by the strongest evidence. For someone weighing 200 pounds, that’s 14 pounds. For someone at 250, it’s about 17.5 pounds. You don’t need to reach an ideal BMI or lose a dramatic amount. That relatively modest reduction is enough to improve how your body processes sugar and responds to insulin. The CDC’s national Diabetes Prevention Program structures this as an intensive 16-week lifestyle intervention, followed by a longer maintenance phase, so the expectation is gradual, steady loss rather than a crash diet.
What to Eat to Lower Blood Sugar
Two dietary patterns have the most evidence behind them for improving blood sugar control: low-carbohydrate eating and the Mediterranean diet. Both work, but a 16-week trial comparing the two in overweight adults found that a low-carb approach produced a 23.2% reduction in A1C, compared to 13.5% with a Mediterranean diet. The low-carb group also saw greater improvements in BMI, waist circumference, blood pressure, and cholesterol.
That doesn’t mean Mediterranean eating is ineffective. It still produced meaningful A1C reductions and is easier for many people to stick with long term because it’s less restrictive. It emphasizes vegetables, whole grains, fish, olive oil, nuts, and legumes while limiting red meat and processed food. A low-carb approach cuts starches and sugars more aggressively, replacing them with protein, healthy fats, and non-starchy vegetables. Either pattern is a significant upgrade over a standard Western diet heavy in refined carbohydrates.
Fiber deserves special attention. Large cohort studies consistently show that high fiber intake (more than 25 grams per day for women, more than 38 grams for men) is associated with a 20 to 30% lower risk of developing type 2 diabetes. Interestingly, the strongest evidence points to insoluble cereal fibers found in whole grains, bran, and seeds, rather than soluble fiber from fruit. Think oats, barley, whole wheat, and flaxseed as daily staples.
The Best Exercise Combination
Walking 150 minutes per week is the baseline recommendation, and it works. But the type of exercise you do matters more than most people realize. A trial published in the Journal of Applied Physiology tested aerobic exercise alone, resistance training alone, and a combination of both in overweight adults. Neither aerobic exercise nor resistance training on its own significantly improved insulin sensitivity. But combining the two produced meaningful improvements in insulin sensitivity, the ability of insulin-producing cells to function properly, and the body’s capacity to clear glucose from the bloodstream on its own.
Aerobic exercise alone did improve one specific marker: how well the liver responds to insulin, measured by fasting insulin levels. That’s valuable but incomplete. Resistance training alone didn’t move any of the key markers. The combination, however, improved everything. In practical terms, this means your weekly routine should include both cardio (brisk walking, cycling, swimming) and some form of strength training (bodyweight exercises, free weights, resistance bands). Three days of each, or combining them in the same session, covers the bases.
Why Sleep Can Make or Break Your Progress
Sleeping fewer than eight hours per night raises insulin levels and worsens insulin resistance, independent of diet and exercise. The relationship is direct: shorter sleep correlates with higher insulin resistance scores, with a strong statistical link. Sleep deprivation increases cortisol, your body’s primary stress hormone, and ramps up sympathetic nervous system activity. Both of these effects push blood sugar higher and make your cells less responsive to insulin. You can eat perfectly and exercise daily, but consistently poor sleep will undermine those efforts. Prioritizing seven to eight hours of actual sleep, not just time in bed, is a non-negotiable part of reversing prediabetes.
How Quickly You Can See Results
Because the A1C test reflects your average blood sugar over the previous two to three months, that’s the minimum window before you’ll see a measurable change on lab work. The CDC’s Diabetes Prevention Program is structured around a 16-week initial phase, which aligns with getting two A1C readings to confirm a trend. Many people see their fasting glucose improve within weeks of dietary changes, but the A1C, which is what your doctor uses to determine whether you’ve crossed back into normal range (below 5.7%), takes longer to shift.
Don’t expect a single perfect month to fix everything. The goal is sustained change over three to six months, with periodic lab work to track your trajectory. If your A1C is at the higher end of the prediabetes range (closer to 6.4%), it may take longer to bring it below 5.7% than if you’re starting at 5.8%.
Tracking What Spikes Your Blood Sugar
Continuous glucose monitors, small sensors worn on the arm that read blood sugar every few minutes, are increasingly used by people without diabetes to understand how specific foods affect them. The appeal is personalization: two people can eat the same meal and see very different glucose responses. A qualitative study of adults with obesity at risk for type 2 diabetes found that wearing a CGM increased self-awareness and motivated healthier food choices. Participants reported changing what they ate after seeing a prominent spike from a previous meal.
The catch is that insurance rarely covers CGMs for prediabetes, so you’d likely pay out of pocket. Clinical consensus on their use outside of diagnosed diabetes doesn’t yet exist, and the evidence base is still developing. That said, if you can afford a two-week trial, it can reveal which foods (white rice, certain breads, sugary drinks) cause the sharpest glucose spikes in your body specifically, giving you actionable data that generic dietary advice can’t.
Medication vs. Lifestyle Changes
Some doctors prescribe metformin for prediabetes, and it does reduce the risk of progressing to type 2 diabetes. But in the Diabetes Prevention Program trial, lifestyle changes outperformed metformin decisively. The lifestyle group, targeting 7% weight loss and 150 minutes of weekly activity, reduced their diabetes risk by 58%. Metformin reduced it by 31%. Lifestyle intervention was nearly twice as effective, and it came with additional benefits like improved blood pressure, cholesterol, and cardiovascular fitness that medication alone doesn’t provide.
Metformin can still be a useful tool, particularly for people who struggle to maintain lifestyle changes or who have additional risk factors. But it’s not the first-line approach for most people with prediabetes, and it’s not a substitute for the dietary and exercise changes that drive the largest improvements.