More and more people are facing concerns about their blood sugar levels. In the United States, about 38 million people have diabetes. Even more—over twice that number—have prediabetes. Many others experience insulin resistance, which can cause fatigue, irritability, and dizziness. These conditions tend to become more common as people get older.
The good news is that exercise can help manage these issues. It is just as important as diet in preventing and treating insulin resistance and diabetes. Exercise can also support weight loss, which is often the most crucial step to stabilize blood sugar levels.
Dr. Donald Hensrud, a specialist in preventive medicine and nutrition, and medical editor of The Mayo Clinic Diet, explains that exercise helps the body process glucose in several ways. While any physical activity is beneficial, the type and timing of exercise can significantly affect its impact.
Why Exercise Matters for Blood Sugar Control
Diabetes has many causes, including genetics, family history, weight, and diet. However, research shows that exercise can significantly lower blood glucose and improve insulin use, regardless of diagnosis.
Dr. Gerald I. Shulman, professor at Yale School of Medicine, notes that exercise allows muscle cells to use glucose from the blood more easily. This not only lowers blood sugar directly but also reduces fat around organs—a key risk factor for diabetes and insulin resistance.
Studies show that regular high-intensity interval training (HIIT) or moderate continuous exercise can reverse prediabetes in nearly 40% of participants. However, it may take months or even years to see lasting results.
Strength Training and Intensity Are Key
Any movement is better than none, and simple activities like walking provide benefits. But research indicates that two types of exercise are most effective for lowering blood sugar: high-intensity workouts and strength training.
A recent study found strength training to be more effective than aerobic exercise at controlling blood sugar in people with Type 2 diabetes. This likely applies to others concerned about blood sugar as well, according to Dr. Shulman.
Both aerobic and strength training increase mitochondria—the energy centers in cells—which helps combat Type 2 diabetes. Strength training, especially when challenging weights are used, tends to be slightly more effective.
Strength training is particularly important for older adults. Insulin resistance and Type 2 diabetes speed up muscle loss with age, especially in women. While walking is good for heart health, it does not build much muscle, says Michael Joseph Gross, author of Stronger: The Untold Story of Muscles in Our Lives.
To be most effective, weights should feel heavy. Research shows that lifting challenging weights lowers blood sugar more than lighter strength training. Combining strength training with high-intensity interval training is also effective for managing blood sugar in people with prediabetes and Type 2 diabetes.
People with diabetes should consult their doctors before making major changes to their exercise routines.
Timing Your Workouts
For people without insulin resistance, the time of day for exercise is less important. But for those with prediabetes or Type 2 diabetes, afternoon workouts may better reduce blood sugar.
This is because blood sugar naturally fluctuates during the day, and insulin sensitivity decreases over time. Exercising in the afternoon is less likely to cause dangerous glucose spikes.
Experts recommend exercising at least three times a week and avoiding more than two days in a row without activity. For people with insulin resistance or diabetes, exercising about 30 minutes after a meal helps prevent blood sugar spikes.
If morning workouts suit your schedule better, avoid eating too many carbohydrates before exercising. Instead, have a small meal with protein and healthy carbohydrates such as fruit, vegetables, or whole grains.
Dr. Hensrud emphasizes that prediabetes and newly diagnosed diabetes respond better to lifestyle changes like diet and exercise than long-term cases. It is important to address insulin resistance early.
“I tell people with new diabetes they’re in control,” he said. “The most important thing is to lose weight through diet and exercise.”
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