Glycaemic Index / Glycaemic Load

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There are so many ‘fad’ diets around these days that when one that actually makes some sense comes around it can be difficult to spot. So when the Low GI, rapidly followed by the Low GL diet, became all the rave a few years ago, it was all too easy to view it with a certain degree of healthy scepticism – which proved to be unfounded; years later it seems that research has only added to the concept that a low GI or low GL diet is the way to eat, not just for weight loss but for health in general.

So what is the difference between GI and GL? Let’s start by having a look at GI. The Glycaemic index is a measure of what effect a given food will have on your blood sugar. It measures the effect of 50g of carbohydrate in any given food on your blood sugar, and foods that make your blood sugar go very high when you consume a quantity that contains 50g of carbohydrate (not 50g of that food, important difference!) have a high GI while those that have very little effect on your blood sugar even when you eat enough of them to eat 50g of carbohydrate are considered ‘low GI’ – and it turns out that these are generally healthy foods to eat.

Refined sugar predictably is the highest GI food you can eat, and any baked, processed foods like cakes/biscuits will also have a high GI. Low GI foods would include meat, fish, eggs and most fruits and vegetables, and there are a whole host of foods that are ‘medium GI’ in between. Carbohydrate based foods such as wheat, pasta, cereal etc are extremely variable; in general wholegrain and ‘brown’ (rice/pasta) are lower GI than their white alternatives.

Shortly after the low GI concept was generally accepted as more than a passing fad, the GL diet came to be. This looks at the effect of a standard sized portion of any given food on your blood sugar. The classic illustration of the difference between GL and GI is carrots. If you eat enough carrots to consume 50g of carbohydrate then this will have quite a dramatic effect on your blood sugar, and as such carrots are considered to be a relatively high GI food. However, in order to eat 50g of carbohydrate in the form of carrots you would need to eat 1.5lb of them – that’s at least a supermarket bag full! The reality is that most of us eat the equivalent of 1 or 2 carrots as a serving, and the carbohydrate in this quantity of carrots has a negligible effect on your blood sugar. So despite being relatively ‘high’ GI, carrots in real life have little effect on blood sugar and so are ‘low’ GL and considered a good food choice.

So what difference does blood sugar make anyway? Well, quite a lot! If we eat foods that make our blood sugars go very high then our bodies will normally release insulin into our blood to either use that sugar or store it as fat; it will do whatever it takes to keep our blood sugar at a normal level because having sugar that is too high or too low for any sustained period is dangerous. This is great in principle but can cause a number of problems in the long term.

Firstly if we consume more of certain types of sugar than we need then our bodies will store this as fat; either on our hips and thighs, or round our waists. Fat stored around the waist in particular will also be stored in the liver and put strain on the internal organs – this can lead to being overweight/obese and to type 2 diabetes, and increases the risk of heart disease, liver disease and various other problems.

Secondly, if we ask our bodies to continually release large quantities of insulin to deal with all the sugar we are consuming, eventually the insulin becomes less effective and so we have to produce more and more just to have the same effect; after long enough, the insulin basically stops having any noticeable impact on our blood sugar and we become ‘insulin resistant’ – this is a fair way down the slippery slope to diabetes and all that comes with it.

A high GI/GL diet can have many other, far- reaching issues in terms of our health, not to mention that if we have a high blood sugar and our insulin acts to bring it rapidly down, this makes us tired, hungry, irritable and in the mood to eat more, well, sugar! This makes us overeat and make bad food choices.

And did I mention that refined sugars (sugar, cakes, biscuits, white pasta/bread etc) can also make us look older than we are because they speed up some parts of the ageing process?

In summary, a high GI/GL diet will make us tired, hungry, grumpy, overweight, ill and old! This is the reason why health experts advise us to fill up on foods that are not sugary – fish, meat, eggs, legumes, low fat dairy, most fruit and vegetables would be the main components of a low GL diet along with small quantities of low GL carbohydrates such as porridge and brown rice etc. It’s a challenge, but people who eat the low GL way tend to feel so much better – and weigh less! – in the long term, what do you have to lose?

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