// Eat to beat diabetes

With type 2 diabetes one of this century’s greatest health challenges, you are highly likely to train clients with the disease during your career. One of the most important pieces of advice you can give these clients is to self-monitor their blood glucose levels, says Morwenna Kirwan.

Most health experts agree that Australia is facing one of the biggest medical challenges of the 21st century. An estimated 275 Australians develop diabetes every day. Over 1.7 million Australians have diabetes and up to half of the cases of type 2 diabetes remain undiagnosed. Fuelled by rising body weights and physical inactivity among the population, it is estimated that by 2031 type 2 diabetes will affect 3.3 million people in Australia. With figures like these, it is highly likely that you train, or will train in the future, a client with diabetes – so it’s worth every fitness professional taking a few minutes to get to grips with the basics of the disease.

Although the statistics make sobering reading, there is still plenty that can be done to reduce the risk of developing type 2 diabetes or help relieve some of the symptoms associated with it. Diet and lifestyle modifications are the cornerstones in the prevention and treatment of type 2 diabetes. The major aims of this approach are to reduce body weight, improve insulin resistance and modify cardiovascular risk factors, which collectively contribute to the threefold increased mortality as a result of heart disease in patients with diabetes.

In the beginning there was insulin resistance

The concept of insulin resistance initially emerged following the discovery of insulin. It was noted that patients with diabetes could be divided into two groups based on their response to insulin, i.e. insulin-sensitive and insulin-resistant, which broadly equates to the modern definitions of type 1 and type 2 diabetes.
In the body, carbohydrates are broken down into glucose, which is used in the body’s tissues as fuel. Under normal conditions, the hormone insulin controls blood glucose (BG) by stimulating certain cells in the body to uptake glucose for storage. Insulin resistance, the condition preceding the development of type 2 diabetes, is when muscle, liver and fat cells do not respond properly to insulin. As a result, the body needs more insulin to help glucose enter cells. The pancreas tries to keep up with this increased demand for insulin by producing more. Eventually the pancreas fails to keep up with the body’s need for insulin. Excess glucose builds up in the bloodstream, setting the stage for diabetes.

How does diet influence diabetes?

It was once believed that carbohydrates and diets high in sugar were the cause of diabetes, but scientists have long known that this is not the case. The scientific evidence, as is stands, actually points to fats, particularly saturates (found mainly in meat and dairy products, pastries and high fat snacks for example) as being involved in the development of diabetes. Not only can fat interfere with insulin metabolism, high fat diets also promote weight gain – a risk factor in itself. Diets rich in carbohydrates tend to be lower in fat and energy (calories) and thus are associated with a reduced risk.

Glycemic index

Until the mid 1990s, the prevailing belief was that people with diabetes should avoid foods that contain so-called ‘simple’ sugars and replace them with ‘complex’ carbohydrates, such as those found in potatoes and cereals. This belief was based on the assumption that simple sugars are rapidly digested and absorbed, exerting a more marked response on BG levels. However, research has shown that the chemical structure of carbohydrates is a poor predictor of glycemic response, with the Glycemic Index (GI) proposed to provide a more physiological classification of carbohydrates. The GI is a numerical system measuring the rise in circulating BG that a carbohydrate triggers – the higher the number, the greater the BG response. So a low GI food will cause a small rise, while a high GI food will trigger a dramatic spike.

Glycemic load

Glycemic load (GL) takes the concept of GI a step further, accounting not only for how rapidly an ingested food causes a rise in BG, but also the portion size of carbohydrate the food contains in an average serving. Thus, the GL more accurately reflects the impact that eating specific foods has on BG and insulin levels.

Some foods with a high GI actually have a low GL. Watermelon, for example, has a GI of 72 (high), but since it’s mostly made up of water and actually contains relatively little carbohydrate (6g/serve), its GL is only 4 (low). On the other hand, white rice has a GI similar to watermelon (72), but a much higher GL of 30, meaning the body will respond with a flood of glucose.

The ranking of foods’ GI and GL uses the following scale:

Scientifically, GI and GL are excellent methods for understanding the effects of carbohydrates on BG levels. However, these values are not easy to calculate and are not labelled on all food products. This is where a good understanding of GI and portion sizes can assist individuals with lowering their BG levels. Consider the contributions of the different macronutrients on the plate; the focus should be on plenty of vegetables, good quality starchy carbohydrates, lean sources of protein and healthy fats.

Advocate the self-monitoring of blood glucose

As a health and fitness professional, one of the most important pieces of advice you can give your diabetic client is for them to measure their BG levels. Diet has a direct impact on glucose levels, so measuring before each meal and two hours after the meal (or snack) can give the client a greater understanding of the effects that their food choices are having on their BG. GI and GL are both important concepts to assist with making healthy choices, but having an objective measure of glucose control is a powerful learning tool which in itself will help clients understand the impact that portion size and carbohydrate choice has on their BG levels.


Blood glucose targets

These are targets for BG levels before and after meals:

  Before meals 2 hours after meals

Type 1 diabetes (adults)

4 to 7 mmols/l

< 9 mmols/l

Type 2 diabetes (adult)

4 to 7 mmols/l

<8.5 mmols/l

It is unlikely that every reading will be in the target range; however, a clear goal can be helpful for improving these levels. For the best results, request your diabetic client completes a seven-day food diary, with their BG measures noted before and two hours post-meals. For those meals outside of the BG recommended ranges, consider offering the client advice to lower the glycemic response, i.e. increase fibre intake, choose a low GI version, reduce portion size and/or include a lean source of protein to lower the GL of the meal.

10 eating tips for managing blood glucose

  • Eat regularly and avoid skipping meals
  • At each meal include low GI carbohydrate foods that are high in fibre – these help maintain the health of the digestive system and level out BG levels
  • Cut down on fat, particularly saturated fats – choose low fat dairy products, grill, steam or oven bake and choose lean sources of protein
  • Eat more fruit and vegetables – aim for five to nine portions a day
  • Include more beans and lentils; try adding them to stews, casseroles and soups, or to a salad
  • Aim for at least two portions of oily fish a week (e.g. mackerel, sardines or salmon)
  • Limit the amount of processed foods, as these are high in salt; flavour foods with herbs and spices instead
  • Drink alcohol in moderation; it is empty calories that can cause cravings for unhealthy foods (e.g. fried food)
  • Avoid diabetic foods or drinks – they are expensive, contain as many calories as ordinary foods and often cause a laxative effect
  • Lose weight – losing even five to seven per cent (five to seven kg for a 100kg person) lowers BG levels and improves insulin sensitivity in the body.

Having diabetes doesn’t mean that you have to eat special food or follow a complicated diabetes diet plan. A diabetes diet is a healthy-eating plan that’s naturally rich in nutrients and low in fat and calories. In fact, it’s the best eating plan for everyone.


Morwenna Kirwan, MHMSc
Morwenna is an Exercise and Behavioural Scientist at CQUniversity in Queensland. Her research is focused on chronic disease self-management, psychology, nutrition and behaviour change. To contact Morwenna email m.kirwan@cqu.edu.au

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