How Does Exercise Affect Blood Sugar Levels?

When you have diabetes, starting a workout routine isn’t quite as straightforward as it may be for others. You can’t simply lace up for a run, show up at a fitness class, or head to the gym on a whim. There are so many moving parts to account for. For example, if you eat a high-carb breakfast to fuel your exercise session, how long and hard should you exercise to “offset” that – plus, should you adjust your insulin dose?

All that uncertainty is enough to give you a splitting headache. And, not to mention, leave you second-guessing your intentions for starting a fitness routine. Exercising can’t be worth the trouble … right?

How does exercise benefit people with diabetes?

That couldn’t be further from the truth. As it turns out, research shows exercise is worth every little bit of trouble. For individuals with diabetes (or any chronic health condition, for that matter), the benefits of sticking to a regular physical activity routine include:

• Decreased insulin resistance: A large body of evidence indicates that exercise can boost the body’s sensitivity to insulin, improving long-term blood sugar control. It doesn’t even take much to see results, either. According to a widely-cited study published in the International Journal of Sports Medicine, just a single bout of exercise can increase insulin sensitivity for at least 16 hours post-exercise.

• Weight loss: By increasing your daily calorie expenditure, exercise could help you shed excess weight. Beyond simply improving your insulin sensitivity, losing just 5 to 10% of your body weight could significantly lower your blood pressure and cholesterol levels – heartening news, given that research shows a close link between diabetes and cardiovascular disease.

• Lowered inflammation levels: Regardless of diabetes type (i.e., type 1, type 2, or gestational diabetes), research shows a link between the condition and chronic inflammation, a risk factor for various diseases like arthritis, chronic obstructive pulmonary disease, and some cancers. Good news: according to this study published in Brain, Behavior, and Immunity, just one 20-minute session of moderate exercise is enough to exert anti-inflammatory effects.

Check your blood sugar levels before, during, and after exercise

Contrary to popular belief, exercise doesn’t always lower your blood sugar levels. Some workouts, like heavy weightlifting, sprints, and competitive sports, increase your body’s stress hormones (e.g., adrenaline). Adrenaline stimulates your liver to release glucose, raising blood sugar levels.

As a result, in general, it’s always a good idea to check your blood sugar thrice: 1) before, 2) during, and 3) after your workout session:

• 30 minutes before exercise: Consider these general guidelines relative to your blood sugar level measured in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).

• <100 mg/dL (5.6 mmol/L): Your blood sugar may be too low to exercise safely. Eat a small snack containing 15 to 30 grams of fast-acting carbohydrates, like fruit, crackers, or glucose tablets.

• 100 to 250 mg/dL (5.6 to 13.9 mmol/L): You’re good to go in most cases.

• 250 mg/dL (13.9 mmol/L) or higher: Your blood sugar may be too high to exercise safely. Take measures to correct the high blood sugar levels before beginning your workout.

• During exercise: Check your sugar levels every 30 minutes. Stop exercising if your blood sugar falls below 70 mg/dL (3.9 mmol/L) or you feel shaky, weak, or confused.

• After exercise: Check your blood sugar level as soon as you finish your workout—and, ideally, several times over the next few hours. The more strenuous your exercise session, the longer your blood sugar will be affected. Consider eating slower-acting carbohydrates, like a granola mix, to keep your blood glucose levels stable.

Combine aerobic exercise with resistance training

While aerobic exercise is traditionally recommended, there’s growing consensus amongst healthcare practitioners that a combination of aerobic and strength training results in better glycemic control and blood lipids for individuals with diabetes than either modality alone.

Here are a few examples of aerobic and resistance training exercises you could try (note: please get your doctor’s OK before starting a fitness routine):

• Aerobic exercise: Swimming, cycling, walking, rowing, running
• Resistance training: HIIT, Pilates, plyometrics, yoga, weight training

Stay on top of your blood sugar levels with Diabetes:M

Remembering to check your blood sugar levels every 30 minutes while exercising can be overwhelming, especially considering you’ll likely be huffing and puffing, working hard—as you should. So let Diabetes:M help. With its nifty Reminders feature, you’ll never have to worry about an accidental hypo- or hyperglycemia episode again. Its Bolus Advisor can also help you manage your food and insulin around workouts. Talk about peace of mind.

Gene Lim

Having witnessed first-hand the debilitating effects uncontrolled diabetes can have on family members, Gene Lim is passionate about using the knowledge she has on the chronic condition to help people with diabetes learn how to best take care of their health while living a full, vibrant life.