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The Energy Advantage

Top Tip to Energize your life

Thoughts on the GI diet

In 2003, at the height of the Atkins diet, I predicted that the fad of low carb diets could not be sustained. Many people tried the diet, like it at first, but soon became all proteined out. There are only so many bacon and egg breakfasts you can eat. Vegetarians and vegans had a hard time to eat enough protein and fat but without the associated carbohydrate found in many plant based foods. And anyway, there is a place for a bowl of golden carrot and lentil soup with crusty wholemeal bread or chick pea, garlic and red onion casserole. Finally Mr Atkins and his best selling book got toppled from the top ten and the British subsidiary of the Atkins Corporation, the producer of the low carb range, was closed in March 2005. But there is still a need for weight reduction and, especially amongst children, not to become obese in the first place. Enter the new GI diet. This is based on the principle that you CAN eat carbohydrate, but that they are not equal. Each food has a glycaemic index (GI) value which relates to the speed with which the food is digested and the sugars absorbed into your bloodstream. The best way to understand this concept is to know more about how the GI value for each food is calculated.

First take your volunteer – a person who does not mind having blood samples taken. Sit them down and insert an in-dwelling cannula into a vein in their arm (the allows regular blood samples to be drawn off without the need to stab with a needle each time!). Take a baseline blood sample and measure the amount of glucose in this. Then ask the volunteer to swallow a drink containing exactly 100 grams of glucose. This will be absorbed rapidly into the bloodstream and can be measured by taking a blood sample every 10 – 15 minutes. Other foods, such as white bread, custard cream biscuits, spaghetti, raisins, ice-cream, custard, grapes (containing a standard amount of carbohydrate) are given individually to the volunteer and the rise in blood glucose measured. The response from the first glucose drink is taken as 100 and all other foods are compared with this. Hence foods are rated between 1 and 100 in the GI diet.

The advice is to eat foods with a low GI value (below 50) since these are the slowly absorbed carbs, and to avoid those over 70 where the carbs are absorbed quickly. The reason for this is that insulin is the hormone which controls your blood sugar level. If you eat a bowl of Cornflakes, white toast with marmalade all washed down with a can of Coke, your blood sugar level will rocket sky high very quickly – and so will your insulin level. Blood sugar levels tend to fall below normal after a high GI food has produced a lot of insulin. This sets up a craving for MORE sugary foods and before you know it, you are on a roller coaster of energy highs and lows. Symptoms of a low blood sugar include sweating, dizziness, feeling weak, poor concentration and sometimes palpitations. Also, as long as insulin remains high, it promotes the storage of fat. This is because the excess glucose in your blood have to go somewhere. They are taken to the liver and converted into fat … which is then deposited around your body (hips, thighs, top of arms, belly). It is far, far better to eat foods with a low GI as they don’t produce the same surge of blood glucose and insulin. Instead they provide your body with a steady supply of blood sugar throughout the day – to maintain mental and physical energy levels and help avoid those cravings for sweet foods.

These low GI foods also encourage the internal biochemistry of the body to go into fat burning mode (as long as insulin levels are normal, or low, fat is released from storage and used as a source of energy). This is not a new concept. The effects of foods on blood sugar levels have been well researched for years – particularly in relation to the prevention and treatment of diabetes. The concept seems even more applicable now because of the nature of our modern food supply. This has become so sophisticated, so over processed, with a huge increase in the use of refined carbohydrates that the effect is that we are overfed and undernourished. So, a switch back to foods with a low GI value will do a lot to take us back to enjoying carbohydrate foods as close as possible to their natural state.

There are plenty of diet books on the market with GI in the title – and these will give the GI rating of foods. However, the GI concept is too simplistic! Enter GL (glycaemic load) – which is a much more helpful term. The GI value only tells you how rapidly the sugars from a particular food are absorbed; it doesn’t tell you about the quantity of that carbohydrate in a typical serving of the food. You need to know BOTH to understand the effect the food will have on blood sugar. For example, wonderful foods such as mangoes, watermelon and grapes have a high GI, but relatively little carbohydrate per portion compared with chocolate (which has a moderate GI value). So look for foods with a GL value. GL has a different index with foods of 10 or under being good, up to 20 are OK and over 20 are to be restricted or avoided. This means that foods with a high GI (such as 57 for dried apricots) which would be “not allowed” in GI terms, are fine in GL (a healthy 4.9 score). In my opinion foods with a low GL are the ones to base your eating habits on. Be warned, the principles of scoring foods according to both GI and GL make sense in theory, but they are difficult to apply in practise. This is because each food has an individual score, but in reality we usually eat a combination of one or more foods.

The best advice is to find a book with lists of foods with GL values - and base your eating habits on those with a low GL. This will guide you towards the good quality carbohydrates, and being able to enjoy them - rather than adding stress to your life in trying to get the calculations "right".

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