Insulin Therapy And Exercise

What is diabetes, and how is it managed? 

Diabetes is a chronic condition that occurs when your body does not produce enough insulin or it cannot use insulin properly.^1,2 Insulin is a hormone produced by the pancreas, and it functions as a key that allows blood glucose (blood sugar) to enter the cells.^1,2 As a result of diabetes, blood glucose levels become too high and, over time, the person can develop health complications, such as heart disease, vision loss, and kidney disease.²

The main types of diabetes are:^1,3

• Type 1 diabetes – the body's immune system attacks, by mistake, the cells that produce insulin and the pancreas stops making insulin.
• Type 2 diabetes – the pancreas does not produce enough insulin, or the body's cells do not respond to insulin as they should. This condition is associated with multiple causes, but obesity and ageing are common risk factors.

Diabetes treatment requires multiple interventions and maintaining a healthy lifestyle. Additionally, if you have type 1 diabetes, you have to take daily insulin by injections or pump. If you have type 2, the treatment usually starts with appropriate diet and exercise, but you may need medication and insulin.^1,3

In this article, we will review the importance of exercise in diabetes management and considerations for insulin therapy before, during and after exercise. 

Insulin therapy

Types of insulin 

There are many types of insulin to treat diabetes. Usually, people who require insulin are prescribed a fast-acting one to take with meals (also called bolus insulin), and a slower-acting one that works through the day (also known as basal insulin):^4,5

Being active with diabetes

Benefits of exercise for people with diabetes

Exercise is important for your health and well-being. If you have diabetes, it can also help improve insulin sensitivity, blood glucose control and weight management, as well as lower cardiovascular disease risk.^6,7 For most people with diabetes it is recommended to exercise 150 min or more of moderate-to-vigorous intensity, at least 3 days/week.⁸

Nonetheless, the variability in blood glucose responses to different types of exercise can make managing physical activity and insulin therapy challenging.⁶ Let’s understand more below.

Types of exercise suitable for individuals with diabetes

Aerobic exercises

These types of exercises include walking, jogging, cycling and swimming. People with both type 1 and type 2 diabetes can benefit from moderate to high volumes of aerobic exercises, as they are associated with lower cardiovascular and mortality risks.⁸

However, in most people with type 1 diabetes, blood glucose levels can fall during aerobic exercise, and hypoglycaemia (low blood glucose) can develop within about 45 min. Therefore, increasing carbohydrate intake, reducing insulin dose, or both is important before starting aerobic exercises.⁶

In people with type 2 diabetes, aerobic exercise training improves insulin sensitivity. The risk of hypoglycaemia is minimal if no medication is used and the condition is managed with lifestyle improvement alone.^6,7 For people taking insulin dosing and timing must be considered before exercising and carbohydrates may be needed.⁶

Strength training or resistance exercise

These types of exercises include exercises with weights, body weight, or elastic resistance bands. Since people with diabetes can develop low muscular strength, strength exercises are important to improve muscle mass, body composition, physical function, bone mineral density, insulin sensitivity, cardiovascular health, as well as mental health.⁸ 

In people with type 1 diabetes, strength training is associated with better blood glucose stability than continuous moderate aerobic exercise, although it could cause a small rise in blood glucose in some people.⁶

In type 2 diabetes, strength training combined with modest weight loss may reduce average blood glucose levels 3x more than compared to calorie-restricted, non-exercising people who lost skeletal muscle mass.⁷

The American Diabetes Association recommends that adults with diabetes engage in 2 or 3 sessions/week of strength exercise on nonconsecutive days.⁸

Mixed exercises

Activities that combine resistance and aerobic exercise are associated with glucose stability and may be superior in controlling blood glucose than either type alone.^6,8 Moreover, doing strength training first results in less hypoglycemia compared to when aerobic exercise is practised first.⁸

Precautions and considerations for exercising with diabetes

Before starting exercise, it is important to ask your healthcare provider about the best types of activities for you and what precautions to take before and after, including:^8,9

• Monitoring glycaemia (blood glucose levels);
• Nutrition;
• Insulin doses and timing of exercise. 

Monitoring glycaemia before, during and after exercise

Because exercise can induce hypoglycemia, especially in people with type 1 diabetes and, in some people with type 2 using insulin, blood glucose monitoring before, during, and after exercise is necessary to create strategies to maintain appropriate levels.^6,8

Hypoglycemia (low blood glucose) events usually occur between 6 to 15 h postexercise but can be prevented with carbohydrate ingestion and adjustment in insulin regimen. On the other hand, exercise-induced hypoglycemia hyperglycemia can also occur if insulin is omitted or reduced before exercise on purpose or if you overconsume carbohydrates.⁸

Appropriate levels of blood glucose depend on individual responses and the type of exercise. For most people, a reasonable range before starting:⁶

• One hour of aerobic exercise is about 126–180 mg/dL. Higher concentrations may be acceptable when protection against hypoglycaemia is needed.
• A session of strength training can be about 90–126 mg/dL because blood sugar concentrations tend to stay relatively stable compared to continuous aerobic exercise.

If your blood sugar is above 240 mg/dL, it may be too high to exercise safely. Test your urine for ketones – substances produced when the body does not have enough insulin to control blood sugar and breaks down fat for energy instead. If ketone levels are too high, you can develop ketoacidosis, a complication that needs immediate treatment.⁹

What to eat for exercising? 

Test your blood sugar levels before exercising and if it is below 100 mg/dL, eat a small snack containing 15-30 g of carbohydrates, for example:⁹

• 2 tablespoons of raisins;
• ½ cup of fruit juice or regular soda;
• glucose tablets.

While exercising, it is also important to drink fluids to stay hydrated!⁹ The most effective drink for low-intensity exercise with up to 45 minutes duration is water. If you are training for longer periods, sports drinks that contain 6–8% carbohydrates and electrolytes are useful to stay hydrated and prevent hypoglycaemia.⁶

How to integrate insulin therapy with exercise?

To complement carbohydrate intake or as an alternative, you can reduce insulin doses. However, keep in mind that insulin dose reductions require planning to maintain adequate levels of blood sugar, and monitoring is needed.^6,8

If you start exercising within 90 minutes after a meal, the following table shows suggested reductions in bolus insulin dose before exercise:⁶

Alternatively, if you are exercising soon after a meal (less than 1 hour), another strategy is to combine a 75% reduction of the bolus insulin dose before exercise and a snack with a low glycaemic index.⁶

FAQs

Can people with diabetes do exercise?

If you have diabetes, you can and should do regular exercises if your healthcare provider does not contraindicate it. Physical activity improves health, well-being, body composition, and insulin sensitivity. It also gives cardiometabolic benefits that usually outweigh immediate risks if you take the necessary precautions. Check with your healthcare provider about the best types of activities for you, and recommendations on monitoring blood glucose, nutrition and adaptations to insulin doses.^6,7,8

What types of exercises should people with diabetes and complications avoid?

If you have diabetes and other health complications, you have to be cautious with certain activities:¹⁰

What time of day should people with diabetes exercise?

Because several variables can influence the relationship between exercise time of day and blood sugar in people with diabetes, there is no strong consensus on this topic.¹¹

For people with type 1 diabetes, there is some evidence that engaging in mild to moderate aerobic exercise may have more tangible health benefits, with less hypoglycemia. In contrast, if they exercise in the afternoon,  resistance exercise is more beneficial than aerobic exercise in managing blood sugar levels.¹¹  

For people with type 2 diabetes, exercise may be beneficial after meals for better blood sugar control.^7,11

Nonetheless, being consistent with your exercises is what gives you health benefits. Therefore, from a practical perspective, any time is optimal for exercise if it suits your routine and individual rhythms.¹¹

How do I start exercising?

Starting exercise is not as hard as it seems. Here are some tips that can help:⁹

• If you’re not physically active, start slowly and add a little more time and intensity gradually until the desired level. For example, you can begin by parking farther from the door, taking the stairs, or walking the dog. 
• Find a physical activity that you like; it is easier if you enjoy what you are doing and commit to it.
• Discuss with your healthcare provider and pick a specific and realistic goal. For example, to be active every weekday for 30 minutes. 
• Ask someone to join! It’s more fun exercising together and it contributes to the routine if you count on each other to show up. 
• Schedule it to become a habit. You can try to fit in 20 to 25 minutes of activity every day or at least every other day. For example, you can invite your co-worker for a walk after lunch. 

What physical activity is recommended for people with diabetes?

There isn’t one type of activity that is recommended for everyone. In general, it’s best to do a mixture of different exercises because each type has different benefits and uses different parts of your body.¹⁰ The most important is to find something that you like and works for you.^9,10

The only recommendation is to do at least 150 minutes per week of moderate-intensity exercises. Those can include:⁹

• Doing housework
• Walking fast
• Bicycling
• Dancing
• Swimming
• Playing Sports

If you use insulin, just keep in mind to monitor your blood sugar before, during and after exercise.⁸

However, if you have diabetes complications or other health conditions, you also must be careful with some types of exercise. See more detailed advice above.¹⁰

Summary

Doing regular exercise is important for overall health and well-being, and people with diabetes can benefit from it, too! It enhances insulin sensitivity, helps maintain blood glucose control, contributes to weight management, and reduces the risk of cardiovascular disease.^6,7 

If you have diabetes, just take some precautions such as monitoring blood glucose, eating and adjusting insulin doses before exercise because physical activity can lead to hypoglycemia.⁸ Moreover, if your blood sugar is above 240 mg/dL exercise should be avoided and urine ketones must be tested.¹¹ If you have other health complications, ask your healthcare provider what types of activities are recommended for you.^9,10

For most people, the best exercises are the ones that they like and fit into their routine and individual rhythms. Consistency in exercising is key to getting the health benefits!^9,10,11