Regular exercise has many positive health benefits in the fight against diabetes, most notably a reduced risk of heart failure, writes Giles Warrington
In recent years, there has been increased media reports on diabetes. In 2003, it was estimated that 194 million people have diabetes and this is predicted to increase to 333 million people by 2025.
In excess of 200,000 patients or 5 per cent of the population in the Republic have been diagnosed with diabetes and a similar number estimated to be undiagnosed. For many, it can be difficult to understand the factors that contribute to this disease and the consequences for long-term health.
Types of diabetes
Firstly, it is important to distinguish between the two main types of diabetes. The first occurs when the body stops producing the hormone insulin and is called type 1 diabetes. Insulin is released from the pancreas when we eat food and is involved in transporting glucose into most tissues of the body.
Type 1 diabetes, usually but not always, occurs before 20 years of age and accounts for 10-15 per cent of all cases of diabetes.
Type 2 diabetes, on the other hand, accounts for 80-85 per cent of diagnosed cases and has traditionally been associated with older adults. In recent years, it is not unusual for teenagers and 20- to 30-year-old adults to be diagnosed. These patients do produce insulin, but the hormone does not work as well as it could because the tissues on which it acts become insulin resistant.
The increase in the prevalence of type 2 diabetes has closely matched the rising levels of obesity. An increase in weight, especially around the waist, is associated with insulin resistance. However, not everyone who is overweight or obese will develop type 2 diabetes.
Some will produce more insulin and maintain normal blood glucose levels, but others will fail to produce enough insulin. Consequently, less glucose is removed from the blood stream and the liver production of glucose increases resulting in a chronic increase in blood glucose levels.
Health implications of diabetes
Chronically elevated blood glucose over a number of years is known to contribute to diabetes-related complications. The most common of these include damage to the eyes, kidneys, blood vessels and nervous system. Cardiovascular disease accounts for approximately 70 per cent of mortality in diabetes patients and a large proportion have high blood pressure and blood lipids. The loss of sensation in the feet, due to peripheral nerve damage, is associated with an increase in ulceration and foot damage.
Diabetes is the single biggest cause of non-traumatic amputation in the US. With these clinical implications, it is important for those at increased risk to prevent the development of type 2 diabetes and those who are diagnosed to manage their blood glucose levels carefully.
Role of exercise in diabetes management
According to leading exercise physiologist Dr Donal O'Gorman, regular physical activity has many positive health benefits, including weight maintenance, blood pressure control and a reduced risk of cardiovascular mortality.
Exercise-training patients with type 2 diabetes lowers their blood glucose response following glucose ingestion and improves their blood glucose control. A single bout of exercise has also been shown to significantly improve the action of insulin on muscle cells and increase glucose transport.
However, this effect is short-lived and will reverse in two to three days. Therefore, patients with type 2 diabetes should be encouraged to exercise at least every second day to maintain the benefits of the previous exercise session.
Exercise training does work better for some people than others. Patients who are recently diagnosed with type 2 diabetes often have a better response to exercise. These patients are less likely to have diabetes related complications and are not as resistant to insulin action.
Having diabetes for a prolonged period increases the risk of cardiovascular disease and these patients often cannot exercise at the same intensity or for the same duration. Therefore, encouraging and educating newly diagnosed patients with type 2 diabetes will likely have the greatest clinical benefit.
The exercise training will also contribute to weight reduction and the development of other complications. Traditionally, aerobic exercise such as walking or cycling has been recommended for patients with diabetes. While the most important element is to find a form of exercise that is enjoyable, there is evidence that other types of exercise are also beneficial.
Resistance exercise, or weight training, has been shown to improve insulin resistance and blood glucose levels. This type of exercise is not often thought about, but does not require lifting heavy weights.
A simple circuit of exercises (with or without external loading) that work muscles in the legs and upper body will provide benefits and help maintain muscle mass.
Interval training is often thought to only be for athletic training. However, alternating between exercise at a high intensity and a low intensity also has benefits for patients with type 2 diabetes. It would be recommended to incorporate a combination of these types of exercise training.
While exercise does have many benefits for patients with type 2 diabetes, exercise is a stress on the body. While everyone would be encouraged to undertake some form of physical activity, if exercise is to be used as part of the treatment of type 2 diabetes, it should be carefully monitored.
Patients should check with their diabetologist or GP before undertaking a treatment programme and be aware if they have any complications. It is advisable to monitor blood glucose levels and blood pressure while regular examination of the feet is encouraged.
Appropriately cushioned footwear should be worn throughout the day, but especially during exercise.
Like anyone undertaking an exercise programme, patients with type 2 diabetes should adhere to appropriate training guidelines developed by a suitably qualified specialist, as well as drink water regularly and especially during and after exercise.
Giles Warrington is a sport and exercise physiologist and lecturer in the School of Health and Human Performance at DCU