Written by: Emily J., MSc RD
Reviewed by: Dr. Vimal Ramjee, MD, FACC
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Looking to improve (or maintain) your metabolic health? Learn the relationship between exercise and blood sugar, including its impact on insulin resistance and weight.
Exercise is a core tenet of improving metabolic health, and research shows the importance of exercise in reducing the risk of chronic disease. However, the why and how behind exercise is not always apparent, other than the general knowledge that it’s good for your health. If you’re looking to improve or maintain your metabolic health, it’s important to understand the relationship between exercise, blood glucose, and insulin resistance, as well as the effects of different types of exercise on your health.
When it comes to improving and sustaining health, exercise is a powerful tool. Regular exercise can help [1, 2]:
The American Heart Association recommends adults get at least 150 minutes per week of moderate-intensity aerobic activity or 75 minutes per week of vigorous aerobic activity (or some combination of the two) . Only about ~20% of Americans meet this recommendation, and in Europe, about 33% of the population is estimated to be physically inactive and sedentary lifestyles are on the rise– which may contribute to the current metabolic health crisis [4, 5].
Beyond the recommendation that we get more exercise so we don’t get sick one day, exercise significantly affects blood glucose, insulin resistance, and weight.
Exercise affects blood glucose in two ways — in the immediate and in the longer term.
In the short term, exercise increases glucose uptake into muscle, both during and approximately 2 hours following a 30-minute session . This means that blood glucose clears the bloodstream faster, which lowers blood glucose levels and is used by the muscle tissue for energy and to replete stores. A recent meta-analysis indicated that even just a 2-minute walk after a meal can mitigate extreme blood glucose responses, though a walk of 30-45 minutes after a meal might be the most valuable strategy in terms of countering hyperglycemia .
Confusingly, exercise can also increase blood glucose levels — but there’s a good reason for this, and it is a normal physiological process. When you exercise without eating before, your liver releases glucose from its stores so your muscles can use it for energy. This process alone may cause blood glucose levels to rise while you are exercising.
High-intensity exercise, like sprinting, max-effort weight lifting, and HIIT exercise, can also cause a spike in blood glucose because your body responds to your hard work by making glucose more available for your muscles to use for energy . This short-term rise in blood glucose due to exercise is normal and not a cause for concern. Exercise is a well-established tool for combatting insulin resistance and mitigating blood glucose excursions throughout the day [8, 9].
In the longer term, exercise has been seen to improve glycemic control in people with Type 2 Diabetes, improve fasting glucose in healthy people, and play a crucial role in preventing metabolic syndrome and associated diseases [10, 11].
Exercise is also one of the key tools for reversing insulin resistance and improving insulin sensitivity. One session of moderate exercise can improve insulin sensitivity for the following 16-48 hours, leading to improved blood glucose levels . However, if you stop your exercise routine for more than 3-5 days, insulin resistance will start to increase.
In other words, exercise can have immediate effects on insulin sensitivity, and even a short workout can improve blood glucose and insulin levels.
Routine exercise over the long term can continue to improve insulin sensitivity, and individuals who are regularly active can bounce back from a period of inactivity quicker than those who do not regularly train . In short, exercise is good for insulin resistance immediately and over time.
We know regular exercise can reduce the risk for chronic disease outcomes and improve glycemic control and insulin resistance in the short and long term, but what type of exercise is most effective at doing these things?
Aerobic exercise uses oxygen and strengthens your heart. Think of endurance exercises like jogging, swimming, or cycling. It impacts almost every part of your health, including mental health, the nervous system, cardiovascular function, skeletal muscle, cancer prevention, and insulin resistance, and may aid in weight loss [13, 14, 15].
Resistance training, or weight lifting (though can be done with resistance bands or the like), is ideal for improving metabolic health because it can help reduce fat mass while retaining muscle mass, which can increase energy expenditure, improve glucose uptake, and regulate blood glucose . It has also been seen to improve a number of metabolic health criteria, like triglyceride levels and reducing waist circumference [17, 18].
HIIT, or high-intensity interval training, is when you complete short, all-out bouts of exercise, like sprinting, followed by a period of rest that is usually double or triple the time of the working interval. For example, in a HIIT session, you’d sprint at your max speed for 20 seconds, followed by a 40-60 second rest, and then repeat. Research has suggested that HIIT may be meaningful for reducing fat mass compared to moderate-intensity training and can contribute to the reduction of weight, blood pressure, and fasting glucose levels in overweight and obese populations [19, 20].
Recent research is reaching a consensus that a combination of aerobic and resistance training is best for reducing mortality and reversing metabolic syndrome [21, 17]. Try 2-3 days a week of aerobic training (minimum of 1 hour per week) and 1-2 days a week of resistance training (1 hour per week). Overall, exercise is effective at managing metabolic syndrome and Type 2 Diabetes and can be an effective tool for reversing insulin resistance [22, 23]).
Ultimately, the best type of exercise is the one that you will do consistently. All exercise can improve metabolic health. A type you will stick to is better than a type that you hate (and will likely discontinue) but has marginally better metabolic health benefits. Keep the following points in mind as you develop your own routine find the cadence and workouts that work best for you.