Diabetes, Exercise, and Hormones
Understanding How Physical Activity Affects Your Blood Sugar
When managing diabetes, diet has the biggest impact on blood sugar control. However, exercise comes in at a close second.
Exercise is a powerful tool that can help lower blood sugar, improve insulin sensitivity, and support long-term health.
The American Diabetes Association (ADA) recommends:
- 150 minutes per week of moderate-intensity aerobic exercise (such as brisk walking, cycling, or swimming)—about 30 minutes, five days a week
- Two sessions per week of resistance (strength) training, working all major muscle groups
Reference: American Diabetes Association. (2024). Standards of Care in Diabetes – 2024. Diabetes Care. https://doi.org/10.2337/dc24-S001
But the relationship between exercise and blood sugar isn’t always straightforward. Hormones significantly influence how your body responds to physical activity. Hormones significantly influence how your body responds to physical activity.
Let’s dive into how exercise, blood sugar, and hormones interact.
Hormones and Exercise: A Balancing Act
The human body has a complex system for managing blood sugar.
The body only has one hormone (insulin) to lower blood glucose. However, it has at least five hormones that can raise it. These include glucagon, adrenaline (epinephrine), cortisol, growth hormone, and norepinephrine.
Why so many?
From an evolutionary standpoint, your body is wired for survival. Running out of blood sugar during times of danger or stress would have been life-threatening.
Thus, the body built in multiple systems to raise blood sugar when needed.
What Happens During Exercise?
- Insulin normally tells cells (especially muscle and fat cells) to take up glucose from the bloodstream and store it.
- During exercise, insulin levels decrease in healthy individuals, and glucagon levels rise.
Glucagon signals the liver to release stored glucose to fuel the muscles.
In people with normal pancreatic function, this fine-tuned dance keeps blood sugar stable during physical activity.
However, for people with type 1 diabetes or type 2 diabetes using insulin, this balance is more difficult.
Injected insulin does not adjust automatically based on the body’s needs. This is because it enters the bloodstream differently compared to insulin naturally secreted from the pancreas.
As a result:
- Insulin levels may be too high during exercise
- The liver’s ability to release sugar may be blocked
- Low blood sugars (hypoglycemia) can occur during or after exercise if adjustments aren’t made
Reference: Colberg, SR. (2019). The Athlete’s Guide to Diabetes: Expert Advice for 165 Sports and Activities. Human Kinetics.
Different Types of Exercise Cause Different Blood Sugar Responses
Moderate, Steady Exercise
Examples:
- Brisk walking
- Light jogging
- Leisure cycling
Effects:
- Generally lowers blood sugar gradually
- Muscles pull in more glucose from the blood, using it for fuel
- Small increases in glucose-raising hormones, but usually well-controlled
Risk:
- Blood sugar may drop during or shortly after activity, especially if insulin or diabetes medications are not adjusted properly.
High-Intensity Exercise
Examples:
- Sprinting
- High-intensity interval training (HIIT)
- Heavy resistance training (like weightlifting)
Effects:
- Causes an immediate rise in blood sugar due to a surge of stress hormones, including:
- Adrenaline (epinephrine)
- Norepinephrine
- Cortisol
- Glucagon
- Growth hormone
These hormones prepare the body to handle stress by raising blood sugar quickly.
However, high blood sugar after intense exercise is often temporary.
Risk:
- Hyperglycemia (high blood sugar) during and shortly after exercise
- Followed by a potential blood sugar drop hours later as muscles work to replenish their energy stores
Reference: Riddell MC, Gallen IW, Smart CE, et al. (2017). Exercise management in type 1 diabetes: a consensus statement. Lancet Diabetes Endocrinol. https://doi.org/10.1016/S2213-8587(17)30014-1
Special Considerations for People Using Insulin
If you use insulin, it’s important to understand how exercise affects your needs:
- After high-intensity exercise, you may experience temporary insulin resistance.
- Blood sugars can remain elevated for one to two hours after intense activity.
- Later, as hormones settle and muscles recover, you may become more insulin sensitive, increasing the risk for late-onset hypoglycemia.
In one study:
- People with type 1 diabetes on insulin pumps experienced blood sugar elevations for nearly two hours after high-intensity interval training.
- Participants with type 2 diabetes showed a similar one-hour spike in blood sugar and insulin levels.
Practical Tips:
- Monitor your blood sugar before, during, and after exercise.
- Be prepared to adjust insulin doses or use carbohydrates strategically depending on the type of exercise.
- Watch for low blood sugars several hours after intense or prolonged exercise sessions.
Reference: Yardley JE, et al. (2013). Resistance versus aerobic exercise: acute effects on glycemia in type 1 diabetes. Diabetes Care. https://doi.org/10.2337/dc12-0962
Summary: What You Need to Know
- Diet has the biggest impact on blood sugars, but exercise is critical too.
- Moderate exercise usually lowers blood sugar right away.
- High-intensity exercise can cause a temporary rise in blood sugar, followed by a possible drop hours later.
- If you use insulin, careful blood sugar monitoring is essential around exercise.
- Exercise is a powerful tool for improving overall health, insulin sensitivity, and long-term blood sugar control.
Exercise can feel complicated when you have diabetes—but with the right knowledge and preparation, it becomes a powerful ally.
References
- American Diabetes Association. (2024). Standards of Care in Diabetes – 2024. Diabetes Care. https://doi.org/10.2337/dc24-S001
- Colberg, SR. (2019). The Athlete’s Guide to Diabetes: Expert Advice for 165 Sports and Activities. Human Kinetics.
- Riddell MC, Gallen IW, Smart CE, et al. (2017). Exercise management in type 1 diabetes: a consensus statement. Lancet Diabetes Endocrinol. https://doi.org/10.1016/S2213-8587(17)30014-1
- Yardley JE, et al. (2013). Resistance versus aerobic exercise: acute effects on glycemia in type 1 diabetes. Diabetes Care. https://doi.org/10.2337/dc12-0962
