There are so many good reasons to exercise. Doctors are even writing prescriptions for it nowadays. It is therefore not surprising that physical activity affects your blood sugar levels, but your blood sugar levels also influence how you respond to exercise. In this article, you will learn:
- How exercise and blood sugar are connected
- Which types of workouts increase and decrease your blood sugar levels
- How you can adjust your training to optimize your blood sugar levels
What is blood sugar or glucose?
First things first: the terms blood sugar and blood glucose levels are synonymous. And for the following reason:
When you eat carbohydrate-rich foods, your body breaks them down into a type of sugar called glucose. Glucose and fatty acids are the body’s main energy sources, and after a meal, fat is stored while glucose is released into the blood—hence the terms blood sugar or blood glucose. The body detects that glucose has entered the bloodstream and triggers the endocrine system (the pancreas) to release insulin, which regulates glucose by prompting cells to absorb it for energy use and storage.
What can cause high or low blood sugar?
Low blood sugar (hypoglycemia) can occur if you do not eat enough carbohydrates, drink alcohol, are sick, or take certain medications.
High blood sugar (hyperglycemia) can occur when you consume many carbohydrate-rich foods, due to lack of sleep, insulin resistance, but also through stress, trauma, or chronic illness. It can also affect how your body responds to exercise. Studies show that people with high blood sugar levels may not fully reap the health benefits of exercise.
To lead a healthy life, it is important to recognize the signs of high or low blood sugar.
Both low and high blood sugar are difficult to recognize and can easily go unnoticed, often leaving symptoms untreated. With a continuous glucose monitor (CGM), you can see in real-time how your diet, sleep, movement, and stress levels affect your blood sugar. Monitoring and managing your blood sugar levels is a great way to stay healthy and avoid metabolic disorders.
Why exercise is good for regulating blood sugar
When it comes to your health, exercise is one of the best things you can do. It should come as no surprise, then, that exercise effectively helps keep blood sugar levels consistent. Your body’s muscles need glucose for fuel, and during exercise, the demand for glucose increases because our muscles are being activated. Exercise also increases the body’s insulin sensitivity, allowing insulin to work more effectively so that blood sugar spikes are broken down faster.
How does exercise affect blood sugar?
It is important to know that different types of exercise affect your blood sugar levels differently. How blood sugar changes during a workout can depend on the following factors:
- Blood sugar levels before exercise
- The type of workout (aerobic or anaerobic)
- The duration of the workout
Intense exercise (anaerobic) is likely to cause your blood sugar to skyrocket, as it can release the hormone adrenaline, which stimulates the liver to release glucose more quickly.
In contrast, exercises performed at a steady pace and moderate intensity (aerobic – short duration) use fat as the primary energy source, meaning blood sugar levels remain stable.
Knowing how your body responds to your workouts helps you avoid blood sugar highs and lows. For example, if you notice a sharp rise during a workout, you can be mindful of what you eat before or during your training and how much fluid you consume. More on that below! Let’s now explore which exercises lower or raise your blood sugar.
What are anaerobic exercises and how do they affect my blood sugar?
Anaerobic activities, such as interval training, are more intense, shorter, and get you out of breath quickly. When you train anaerobically, your body primarily consumes glucose, meaning it draws on the glucose (glycogen) stored in the muscles and liver—which is why your blood sugar spikes during these exercises to meet your body's demands. This also means that the spikes occurring during high-intensity training are no cause for concern. The body is responding as it should. That is exactly what you want your body to do.
Examples of anaerobic exercises include: interval training, sprinting, weightlifting, strength training, spin classes, high-intensity interval training (HIIT), Pilates.
What are aerobic exercises and how do they affect blood sugar?
Aerobic exercises are activities that increase your heart rate at a steady pace and low-to-moderate intensity. These are exercises where you can generally hold a conversation with others. Unless you’re swimming ;) In aerobic exercise, the body does not need to draw on glucose stores (glycogen) in the liver; meaning the body does not need to generate immediate energy spikes, but instead taps into energy from fats. This means your blood sugar generally remains stable or even drops slightly.
Examples of aerobic exercises include: swimming, cycling, jogging, walking, rowing, Zone 2 cardio, Ashtanga, Vinyasa, Power and Hot Yoga
Fasted exercise: Is working out on an empty stomach good for my blood sugar?
Fasted exercise means you work out on an empty stomach. You achieve this by fasting overnight and exercising first thing in the morning or before your first meal. The idea is that your body has depleted its glucose stores by the time you train and can more easily access stored fat than in a fed state. However, this practice can lead to a drop in blood sugar levels during training. This drop is a sign that your body lacks sufficient energy (which makes recovery more difficult). As a result, you put your body under significant stress, lose fitness instead of gaining it, and increase the risk of injury as well as your stress levels.
How your menstrual cycle affects your training and blood sugar
Most women are aware that their bodies go through different phases during the menstrual cycle. However, many are not aware of how strongly these fluctuations affect their bodies. Sleep, sexual function, and metabolism are all connected to the endocrine system. The endocrine system regulates the menstrual cycle alongside our blood sugar levels. This explains why hormonal phases can influence glucose metabolism during exercise. In other words, a workout that seemed easy in one phase and resulted in flat blood sugar levels might feel harder and lead to higher blood sugar levels in another phase.
The hormones released during the various menstrual phases appear to affect the dependence on glucose as an energy source as well as the glucose response to food and stress. Hello Inside has developed the Hello Hormones program to show how your blood sugar levels change throughout your cycle. This allows you to optimize your training and glucose response.
Our tips:
We have put together a few tips on how you can optimize your blood sugar based on your workouts, and vice versa.
You can maximize the positive effects of a workout on your blood sugar by incorporating the following tips into your training routine:
General measures:
- Choose a type of exercise that fits your menstrual cycle to feel your best.
- Watch for drops in blood sugar and refuel (ideally a mix of protein and carbohydrates, e.g., yogurt with berries).
- If training lasts longer than 90 minutes, prepare a small snack to consume during your workout (e.g., a banana or 1-2 energy chews).
- Incorporate fasted training by doing 15-20 minutes of HIIT or an aerobic exercise in the morning.
- If you train in the evening, opt for a gentle workout to help you sleep and recover better. (Bonus: Good sleep positively affects blood sugar levels the next day.)
How to prevent your blood sugar from getting too low:
- Keep your body moving by taking a 15-minute walk, taking the stairs, or standing up to stretch every 20 minutes from your desk.
- Avoid hot baths, saunas, and steam rooms after training.
- Do not train later than 2 hours before bedtime.
To avoid blood sugar spikes:
- Do light to moderate exercise before your first meal.
- Try taking a walk after meals: Studies show that moving within 30 minutes of a meal significantly lowers blood sugar levels.
Key takeaways
Glucose serves as fuel for your muscles during exercise. When you perform aerobic exercises like walking or swimming, your blood sugar levels remain stable or potentially decrease. When you do anaerobic (intense) exercises like weightlifting, your blood sugar levels will rise quickly and potentially even spike.
Fasted exercise and aligning your training with your menstrual cycle can both boost your glucose metabolism.
It is recommended to measure your blood sugar before and after exercise. Using a CGM makes this easier and allows you to measure your blood sugar even during workouts. Based on the results, you can determine where your blood sugar levels should be during training and how you respond. For example, you can optimize your energy levels before an anaerobic workout, or if you are training fasted and notice your blood sugar dropping, you can have a prepared snack on hand.
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