Exercise and Diabetes

By Nathan 'The Wizard' Harman – former National Cycling Champion & Bodybuilding Contest Prep Specialist www.probodeez.com

Knowing that you have to exercise and how to actually do it are two totally different things. When I was first diagnosed with diabetes at the age of 11, I had been a competitive cyclist for year and didn't have a clue what diabetes was. It wasn't until being diagnosed as a type 1 diabetic, that I learnt how complex and dangerous the illness actually is.

Diabetes is a common life-long health condition. There are a massive 2.8 million people diagnosed with diabetes in the UK and an estimated 850,000 people who have the condition but don't know it. Diabetes is a condition where the amount of glucose in your blood is too high because the body cannot use it properly. This is because the islets of Langerhans in the pancreas do not produce any insulin, or not enough, to help glucose enter your body's cells in the liver, muscle and fat tissue from the blood, storing it as glycogen in the liver and muscle, or the insulin that is produced does not work properly (known as insulin resistance).

Diabetes mellitus type 1 (type 1 diabetes, insulin dependant diabetes mellitus (IDDM) or, formerly, juvenile diabetes) is a form of diabetes that results from autoimmune destruction of insulin-producing beta cells of the pancreas. The subsequent lack of insulin leads to increased blood and urine glucose. The classical symptoms are polyuria (frequent urination), polydipsia (increased thirst), polyphagia (increased hunger), and weight loss.

Diabetes mellitus type 2 – formerly non-insulin-dependent diabetes mellitus (NIDDM) or adult-onset diabetes – is a metabolic disorder that is characterised by high blood glucose in the context of insulin resistance and relative insulin deficiency. Diabetes is often initially managed by increasing exercise and dietary modification. If the condition progresses medications may be needed. Often affecting the obese, diabetes requires patients to routinely check their blood sugar.

Type 2 diabetes usually appears in people over the age of 30- 40 also known as adult onset diabetes, and accounts for between 85 and 95 per cent of all people with diabetes and is treated with a healthy diet and increased physical activity to begin with. In addition to this, medication and/or insulin is often required if the condition becomes worse. In most type 2 diabetics cases this is why they are in the position in the first place. Exercise and a reduction in body fat totals (by a combination of exercise and diet) could prevent type 2 diabetes from happening.

But please, before jumping into any exercise program, get your doctor's OK to exercise — especially if you've been inactive and, even if you are an advanced trainer newly diagnosed with diabetes (this illness is not to be taken lightly and can cause death at any time). Discuss with your doctor which activities you're contemplating and the best time to exercise, as well as the potential impact of medications on your blood sugar as you become more active; over time your knowledge will increase and control on your diabetes will become more manageable from self-control.

Insulin and Exercise

So now we have a better understanding about the different types of Diabetes, it's important to take look at a non-diabetic and diabetic insulin function when exercising.

During exercise, whole-body oxygen consumption may increase by as much as 20 fold, and even greater increases may occur in the working muscles. To meet its energy needs under these circumstances skeletal muscle uses, at a greatly increased rate, its own stores of glycogen and triglycerides, as well as free fatty acids (FFAs) derived from the breakdown of adipose tissue, triglycerides and glucose released from the liver. To preserve central nervous system function blood glucose levels are remarkably well maintained during exercise. Hypoglycaemia during exercise rarely occurs in non-diabetic individuals; however, some individuals do suffer from reactive hypoglycaemia, or postprandial hypoglycaemia, a medical term describing recurrent episodes of symptomatic hypoglycaemia occurring within four hours after a high carbohydrate meal (or oral glucose load) in people who do not have diabetes. The metabolic adjustments that preserve normoglycaemia during exercise are, in large part, hormonally mediated. A decrease in plasma insulin and the presence of glucagon (a hormone which acts in the opposite way to insulin) appear to be necessary for the early increase in hepatic (liver) glucose production during exercise. During prolonged exercise, increases in plasma glucagon and catecholamine's appear to play a key role. These hormonal adaptations are essentially lost in insulin-deficient patients with type 1 diabetes. As a consequence, when such individuals have too little insulin in their circulation due to inadequate therapy, an excessive release of counter insulin hormones during exercise may increase already high levels of glucose and ketone bodies and can even precipitate diabetic ketoacidosis. Conversely, the presence of high levels of insulin due to exogenous insulin administration can attenuate or even prevent the increased mobilization of glucose and other substrates induced by exercise and hypoglycaemia may ensue.

Similar concerns exist in patients with type 2 diabetes on insulin or sulfonylurea (drugs used to treat diabetes) therapy; however, in general, hypoglycaemia during exercise tends to be less of a problem in this population. Indeed, in patients with type 2 diabetes, exercise may improve insulin sensitivity and assist in diminishing elevated blood glucose levels into the normal range by increasing tissue sensitivity.

It's important to take note that depending on the exercise, duration and intensity will have different effects on glucose levels, and will cause the blood glucose levels to go low (hypoglycaemia) or high (hyperglycaemia). Diabetes is such a complex illness that it will affect each individual differently and with trial and error you will learn to have better control.

Below is a list of things that need to be considered when exercising with Diabetes, also depending what exercise you are actually doing will also affect factors of diabetic control.

Things to consider when planning your training

  • Have you exercised before?
  • How old are you?
  • When does your insulin peak?
  • What types of exercise are you going to do and when?
  • When is your main meal and will it be carbohydrate based?
  • What is your glucose 30min prior to training and what are your pre exercise blood glucose?
  • What type of carbohydrate will you carry during exercise?
  • Will the temperature be very hot or cold?
  • Will you have plenty of fluids available?
  • What snacks will you have post exercise to avoid delayed hypoglycaemia?

If you have Type 1 diabetes, you may need less insulin or more food or both when you exercise. Crazy as it sounds, trial and error over time will help you determine what insulin or food changes your body will need for safe blood sugar levels during exercise (our diabetes specialist nurse or doctor will be able discuss the best plan of action). The extra food you eat to provide sugar for exercise should not be subtracted from your meal plan. Blood sugar testing before and after exercise helps you know if the changes you make in your insulin or your food intake or both were right for you. If you are starting a new exercise and, especially if the exercise is done for a long time, you will need to also test blood sugars during exercise. Keeping careful records will help you establish the pattern of your blood sugar response to exercise; you will soon learn with diabetes that one day is never the same and careful monitoring of blood glucose levels is needed for health and optimum performance in you chosen sport.

You may prefer to adjust your insulin for exercise. This would be the best action to take if you are trying to lose weight and are doing planned exercise. Reduction in the amount of rapid or short acting insulin prior to exercise will reduce the amount of extra food you might have to eat to prevent or treat hypoglycaemia. If you have certain days of the week when you are very active and other days when you get very little exercise, your insulin regimen may be adjusted to match these changes in your exercise pattern. If you notice a pattern of decreased blood sugar levels after you begin exercising, your intermediate or long-acting insulin doses may need to be decreased. Your doctor or nurse should be asked about adjusting your insulin for exercise.

So what should my blood glucose levels be when exercising?

Lower than 5.6 mmol/L. Your blood sugar may be too low to exercise safely. Eat a small carbohydrate-containing snack, such as fruit or crackers, before you begin your workout.

5.6 to 13.9 mmol/L. You're good to go. For most people, this is a safe pre-exercise blood sugar range.

13.9 mmol/L or higher. This is a caution zone. Before exercising, test your urine for ketones — substances made when your body breaks down fat for energy. Excess ketones indicate that your body doesn't have enough insulin to control your blood sugar. If you exercise when you have a high level of ketones, you risk ketoacidosis — a serious complication of diabetes that needs immediate treatment. Instead, wait to exercise until your test kit indicates a low level of ketones in your urine.

16.7 mmol/L or higher. Your blood sugar may be too high to exercise safely, putting you at risk of ketoacidosis. Postpone your workout until your blood sugar drops to a safe pre-exercise range.

This gives a good insight into exercise and diabetes and having to make life changes in order to be on top of glucose control. Diabetes is one illness not to be messed with and complications can include blindness, kidney failure, neuropathy and feet damage, arterial disease, stroke, heart attack and death. Please remember that everything that has been covered in the article is just a guideline and before exercising please consult your diabetes specialist doctor or nurse.