By Matt Kinahan
2023 UBC PharmD Candidate
Have you found it difficult to control your blood sugars? You’re not alone in this challenge. We are here to support you. In this article, we’ll talk about how regular exercise can improve your overall health and well-being, while also making it easier to manage your blood sugar levels. We’ll also address some of the barriers to exercise that are specific to individuals with diabetes. And hopefully we’ll leave you feeling motivated to include regular exercise as an important part of your diabetes management routine.
Benefits to Physical and Mental Health
Diabetes can have a significant effect on mental health. It can feel like an endless battle, fighting every day to keep blood sugar levels under control. Exercise can improve psychological well-being and has been shown to improve symptoms of depression, regardless of the duration or intensity of the exercise (1). Nevertheless, some people may still have some anxiety about inconsistent blood sugar levels or hypoglycemia (and even hyperglycemia) during or after exercise.
Whether you have Type 1 Diabetes (T1DM) or Type 2 Diabetes (T2DM), exercise is important for your overall physical health. A consensus statement in The Lancet: Diabetes & Endocrinology says that 60% of people living with T1DM are overweight or obese, 40% have high blood pressure and 60% have abnormal fat levels. Adults with T1DM who exercise regularly were more likely than inactive individuals with T1DM to meet blood sugar and blood pressure targets. They also lost weight, which contributed to lower fat levels and fewer chronic diseases. And those who exercised regularly were able to reduce the amount of insulin needed (2). An article in Diabetes Care found that, for individuals with T2DM, exercise improves blood pressure and cholesterol levels, while also lowering the risk of cardiovascular disease. Physical activity can improve insulin sensitivity in people living with T2DM for up to 3 days after the activity. Thus, exercise provides a longer duration of controlled blood sugar levels in T2DM. This is especially the case when you take a structured approach to physical activity (e.g., combining resistance training and aerobic exercise) (1).
What Happens to Blood Sugars When You Exercise?
Energy use during exercise depends on exercise intensity and duration. Your body stores energy as carbohydrates in the muscles, the liver and in water outside of cells, though most energy is stored as fat. High-intensity workouts will use energy from carbohydrates almost exclusively, because energy is needed right away and it takes time and significant oxygen to convert the fats into energy. Ironically, during high-intensity exercise, glucose production can exceed glucose use, which may cause sustained high blood glucose (BG) levels after exercise. Because of this, it is best to do high-intensity workouts of only short duration (e.g., sprints) (3).
Mild to moderate-intensity activities will use energy stored in muscles and from blood glucose first, then pull energy from fats. For prolonged activities, such as a long run, energy stored in the muscles will be used for the first 20 to 30 minutes, then blood glucose and additional glucose generated by the liver will be used, along with some fats. The energy coming from glucose and fats will be similar, with fats contributing much more of the energy needs only after 90 to 180 minutes (3). That’s right, it takes a long time before we burn energy stored as fat!
In general, insulin levels decrease during exercise, so blood sugars move into muscles due to muscle contractions, rather than as a response to insulin. The exact reason for this isn’t known, but we do know that being physically active reduces the amount of insulin you need (3).
How Much Exercise is Necessary?
Every effort counts, including everyday activities, such as taking the stairs at work or vacuuming at home. Diabetes Canada recommends moderate to vigorous-intensity aerobic exercise for 30 minutes per day, five days a week and resistance exercises two to three times a week (4). To make it easier, you might do three 10-minute activities each day. If you find these targets difficult to achieve, building up to them is a great goal!
Some examples of aerobic exercises include walking, bicycling, and jogging. Regular aerobic exercise will lower your blood sugars immediately and improve cardiovascular fitness. Resistance exercises include weightlifting using weight machines, free weights, resistance bands, or even your own body weight (1). Since resistance exercises initially use only the energy stored in muscles, lifting weights before aerobic exercise can delay the drop in blood sugars during exercise (3,5). Over time, resistance exercises will increase lean muscle, allowing your body to burn calories throughout the day, even when you’re at rest, which improves weight control (1,3).
Are there Specific Concerns for Diabetes and What Can We Do About Those?
Exercising is a very effective for regulating post-meal blood sugars. But many people are still concerned about low blood sugars occurring during or after exercise. Some people also find that their blood sugars are unpredictable, perhaps going low after a workout on one occasion, but going high after the same workout at another time. There are many additional factors that can affect blood sugar levels before, during and after a workout, such as time of day, emotional state, hydration, and food intake. These factors are especially important for individuals with T1DM.
Some suggestions to improve blood sugar management during exercise:
- Whenever possible, plan your activities. If you are participating in an unplanned activity, check your blood sugar levels before exercising. If BG is less than 8 mmol/L, you will likely need to eat a source of carbohydrates before exercising, unless the activity is brief (< 30 minutes). If BG is > 13 mmol/L, check for ketones and do not exercise until BG is at normal levels.
- Wear a sensor. Sensors can track sugar levels throughout your workout, making it easier to know if you’re trending low and need to have a high-carbohydrate snack.
- Monitor more regularly over the next few days. Increased insulin sensitivity can last for up to 36 hours after significant exercise, so hypoglycemia can occur long after you’ve finished your activity. If bedtime BG levels are low, have a snack containing carbohydrate and protein (e.g, an apple with peanut butter) before bed to reduce risk of overnight hypoglycemia.
- Decrease your insulin dose. Reducing your pre-meal insulin dose reduces the risk of hypoglycemia both during and after exercise. The risk of hypoglycemia is highest if exercise occurs during the first hour or so after injection of fast-acting insulin (as it is rising to peak levels). Please ask us if you need assistance with adjusting your insulin dose.
- Include resistance training prior to aerobic exercise. Resistance training helps to delay the decrease in blood glucose levels, thus helping to maintain steady levels and minimize hypoglycemia (2).
- Keep a fast-acting carbohydrate with you. The risk of hypoglycemia during exercise is minimal; however, it is important to always carry a fast-acting carbohydrate when you exercise and check your sugar levels before, during and after exercising (4,6). If you are unable to recognize symptoms of low blood sugars, exercise with someone who can get help for you.
- Stay hydrated. Drink water before and after exercising, and during exercise if physical activity is strenuous or prolonged. Water is the best choice. Sports drinks often contain calories, sugar, and electrolytes, which are usually needed only by endurance athletes.
- Check your feet after exercise. If you have peripheral neuropathy or peripheral arterial disease, check for blisters and/or reddened areas after any exercise session.
Making healthy lifestyle choices is important for everyone, not only for individuals with diabetes. Being physically active has profound benefits on both physical and mental health. We can help you to safely incorporate exercise into your diabetes management plan.
- Colberg SR, Sigal RJ, Fernhall B, Regensteiner JG, Blissmer BJ, Rubin RR, et al. Exercise and type 2 diabetes: the American College of Sports Medicine and the American Diabetes Association: joint position statement. Diabetes Care. 2010;33(12):e147-67.
- Riddell MC, Gallen IW, Smart CE, Taplin CE, Adolfsson P, Lumb AN, et al. Exercise management in type 1 diabetes: a consensus statement. Lancet Diabetes Endocrinol. 2017 May;5(5):377-390.
- Chapter 9: Endurance Training and Type 1 Diabetes. In: Christo C, Cleave B, Fredericks C, Gorecki K, Hamilton C, MacNeill G, et al, editors. Building Competency in Diabetes Education: Advancing Practice. 3rd ed. Toronto: Canadian Diabetes Education; 2014. p. 1-51.
- Physical Activity [Internet]. Diabetes Canada. Toronto: 2022 [cited 2022 Nov 17]. Available from: https://www.diabetes.ca/managing-my-diabetes/tools—resources/physical-activity.
- Connected in Motion’s Virtual Slipstream: Canada 2020 event [Internet]. 2020 [cited 2022 Nov 17]. Yardley J. Available from: https://www.youtube.com/watch?v=8LRSX1bCkPQ.
- Get Active! [Internet]. Centers for Disease Control and Prevention. Available from: https://www.cdc.gov/diabetes/managing/active.html.