Keto Unlocks Exercise Benefits for People With High Blood Sugar

TL;DR

A Virginia Tech study published in Nature Communications found that a ketogenic diet normalized blood sugar within one week in hyperglycemic mice and remodeled their muscles to respond dramatically better to aerobic exercise. Diet and exercise aren’t simply additive — keto specifically enables exercise benefits that high blood sugar otherwise blocks.

If you have high blood sugar and exercise isn’t delivering the results you expect, the problem might not be your workout. It might be your metabolism.

A new study from exercise scientist Sarah Lessard at Virginia Tech’s Fralin Biomedical Research Institute offers a compelling explanation — and a surprising solution.

The Problem: High Blood Sugar Blocks Exercise Benefits

📚 Why This Matters

One of the strongest predictors of health and longevity is VO2peak — your body’s ability to take in and use oxygen during exercise. People with high blood sugar often can’t improve this metric, even with consistent training.

Exercise is supposed to make your heart stronger, build muscle, and boost cardiovascular fitness. For most people, it does. But Lessard’s earlier research found something troubling: people with chronic high blood sugar (hyperglycemia) don’t get the same aerobic benefits from exercise that healthy people do.

Their muscles struggle to take up oxygen more effectively in response to training. The exercise is happening, but the adaptation isn’t.

The Study: Keto + Exercise Together

Lessard’s team fed hyperglycemic mice a high-fat, very low-carbohydrate ketogenic diet and had them exercise on running wheels. The results were striking.

🎯 Key Findings

Blood sugar normalized in one week — as though the mice didn’t have diabetes at all
Muscles remodeled to become more oxidative (better at using oxygen)
Mice developed more slow-twitch muscle fibers, which support endurance
Bodies used oxygen more efficiently, a sign of higher aerobic capacity
The combination of keto + exercise produced benefits that neither alone could achieve

"After one week on the ketogenic diet, their blood sugar was completely normal, as though they didn't have diabetes at all. Over time, the diet caused remodeling of the mice's muscles, making them more oxidative and making them react better to aerobic exercise."

— Sarah Lessard, Associate Professor, Fralin Biomedical Research Institute

Why Diet and Exercise Aren’t Simply Additive

This is the most important takeaway from the study. We tend to think of diet and exercise as two separate levers for health — eat better and move more. But Lessard’s work suggests something more nuanced: they interact at the cellular level.

High blood sugar prevents muscles from adapting to exercise. By lowering blood sugar through a ketogenic diet, the muscles can finally respond to training the way they’re supposed to.

"What we're really finding is that diet and exercise aren't simply working in isolation. There are a lot of combined effects, and so we can get the most benefits from exercise if we eat a healthy diet at the same time."

— Sarah Lessard, Virginia Tech

Think of it this way: if your blood sugar is chronically elevated, exercise is like trying to build a house on a cracked foundation. The keto diet fixes the foundation, and then exercise can do its job.

A Historical Perspective

📚 Keto Before Insulin

In the 1920s — before the discovery of insulin — the ketogenic diet was already being used to manage diabetes because of its ability to lower blood sugar. This isn’t a new idea. Modern science is simply catching up with the mechanisms that explain why it works.

The ketogenic diet has also shown benefits for epilepsy, Parkinson’s disease, and other neurological conditions. The common thread? Shifting the body’s fuel source from glucose to ketones appears to have wide-ranging metabolic effects.

What About Other Diets?

⚠️ Important Nuance

This study was conducted in mice, and human trials are the next step. Lessard also notes that a strict keto diet is challenging to follow long-term. Any strategy that effectively lowers blood sugar — including less restrictive approaches — may help unlock exercise benefits.

Lessard is careful to point out that the key mechanism is blood sugar reduction, not necessarily ketosis itself. A Mediterranean-style diet that keeps blood sugar low through unprocessed foods could potentially offer similar benefits, though keto’s rapid blood sugar normalization (one week!) is hard to match.

What You Can Do

🎯 Practical Takeaways

If you have high blood sugar and exercise isn’t working: Consider addressing blood sugar through diet first, then layering in exercise
The order may matter: Fixing metabolic health creates the conditions for exercise to be effective
Keto is one tool: Any approach that normalizes blood sugar could help — talk with your doctor about what’s sustainable for you
Stay hydrated and replenish electrolytes: When starting keto, electrolyte balance shifts significantly — magnesium, sodium, and potassium become especially important
Be patient with exercise: Once blood sugar normalizes, give your muscles time to remodel and adapt

The Bottom Line

This study challenges the “just exercise more” advice that people with metabolic issues often hear. If high blood sugar is blocking your body’s ability to adapt to exercise, no amount of running will fix it alone.

Diet and exercise work together — but diet may need to come first. By normalizing blood sugar (whether through keto or another approach), you give your muscles the ability to actually respond to training. That’s when exercise starts delivering on its promise.

Human trials are next. We’ll be watching closely.