How to Manage Your Blood Sugar With Exercise

New York Times

19-05-2025

These days, more and more of us have to worry about our blood sugar.
Some 38 million Americans have diabetes, and more than two times that number have pre-diabetes. Many millions more have some form of insulin resistance, which can make you tired, irritable and even dizzy. And all of these conditions become more common as we age.
The good news is that exercise can help. It's at least as important as your diet for preventing and treating insulin resistance and diabetes. It can also help you lose weight, which is often the most important step in leveling out blood sugar.
Exercise has several unique ways to help your body process glucose, said Dr. Donald Hensrud, a specialist in preventive medicine and nutrition and medical editor of 'The Mayo Clinic Diet.' And while any exercise is good for you, the type of movement you choose and when you do it can play a big role in how much it helps.
Here are some things you should think about when planning workouts, according to experts.
Exercise is essential to managing blood sugar.
The causes of diabetes are complex. Family history, genetics, weight and diet certainly play a role. But it's clear that exercise can dramatically lower your blood glucose, regardless of your diagnosis, and improve how well your body uses insulin.
In fact, research has shown that exercise is generally more effective at preventing diabetes than medication (though it is important to use all types of treatment). During exercise, your muscle cells can more easily use the glucose in your blood. This lowers blood sugar directly and can also reduce the fat around your organs, an important risk factor for diabetes and insulin resistance, said Dr. Gerald I. Shulman, a professor of medicine and physiology at the Yale School of Medicine.
In particular, studies show that regular high-intensity interval training or moderate continuous exercise can make a difference, reversing pre-diabetes in almost 40 percent of the participants — although it could take months or even years for many people to see long-lasting changes.
Prioritize strength training and intensity.
Any movement is better than none, and simply going for a walk can have benefits. But according to research, the two most effective ways to lower your blood sugar through exercises are high intensity workouts and strength training.
A recent study found strength training was significantly more effective for controlling blood sugar levels than aerobic exercise for people with Type 2 diabetes, and this likely holds true for other people worried about their blood sugar, Dr. Shulman said.
Also, both aerobic exercise and strength training create more mitochondria, which can help fight Type 2 diabetes, but weight lifting appears to be slightly more effective than aerobic exercise, assuming you are pushing yourself, Dr. Shulman said.
Strength training is especially important for older people, since insulin resistance and Type 2 diabetes accelerate the normal loss of muscle and strength that comes with age, particularly for women. And while walking is good exercise for the heart, it generally won't build much muscle, said Michael Joseph Gross, author of 'Stronger: The Untold Story of Muscles in Our Lives.'
The way you strength train is also important, he added. To be most effective, the weights should feel heavy. A systematic review of the research found lifting challenging weights helped lower blood sugar more effectively than low-intensity strength training.
Consider alternating your strength training session with high-intensity interval training, which has been shown to be especially effective in managing blood sugar for people with pre-diabetes and Type 2 diabetes. If you have diabetes, consult a doctor before radically changing your fitness regimen.
When is the best time to work out?
If you do not have insulin resistance, the time of day you work out doesn't matter much.
But for people with pre-diabetes and Type 2 diabetes, studies suggest that afternoon exercise tends to help reduce blood sugar levels. This is because blood sugar rises and falls in regular patterns over the course of the day, and as the day goes on, the body becomes less insulin sensitive. Thus afternoon exercise is typically less likely to cause dangerous glucose spikes.
Experts recommend working out at least three days per week with no more than two days in a row without activity. For people with insulin resistance, including diabetes, the best time to exercise is about 30 minutes after starting a meal to prevent blood sugar spikes.
If morning workouts fit better with your schedule, try not to eat too many carbohydrates beforehand and start the day with a small meal of protein and healthy carbohydrates like fruit, vegetables and whole grains.
Pre-diabetes and new-onset diabetes are much more responsive to lifestyle changes like diet and exercise than longer-term cases, Dr. Hensrud said, so it's important to address insulin resistance as soon as possible.
'I tell people with new diabetes they're in control,' he said, 'and the most important thing to do is decrease weight through dietary changes and exercise.'