(GI) is a numerical system of measuring how fast a carbohydrate triggers a rise in circulating blood sugar – the higher the number, the greater the blood sugar response. So a low GI food will cause a small rise, while a high GI food will trigger a dramatic spike. A GI of 70 or more is high, a GI of 56 to 69 inclusive is medium and a GI of 55 or less is low.
The Glycemic Load (GL) is a relatively new way to assess the impact of carbohydrate consumption. It takes the Glycemic Index into account, but gives a fuller picture than the Glycemic Index alone. A Glycemic Index score tells you only how rapidly a particular carbohydrate turns into sugar – but it doesn’t tell you how much of that carbohydrate is in a serving of a particular food (i.e. the GI is a qualitative measure, whereas the GL is a quantitative measure). You need to know both things to understand a food’s effect on blood sugar. The carbohydrate in watermelon, for example, has a high GI, but there isn’t a lot of it, so watermelon’s Glycemic Load is relatively low. A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium and a GL of 10 or less is low. Foods that have a low GL almost always have a low GI. Foods with an intermediate or high GL range from very low to very high GI. There is a detailed table in the Resources section showing the GI and GL of common foods.
The Glycemic Index and obesity
You may be surprised to know that it is not just the number of calories you eat that results in weight loss or weight gain. This is because calorie counting does not take into account the Glycemic Index and the hormonal response to food. Calorie counting can be helpful but should certainly not be the sole focus for weight loss. The reason why a low GI carbohydrate diet helps weight control is because it helps you feel satisfied after a meal and it both minimizes insulin levels after consumption and maintains insulin sensitivity.
Case Study: Carol
Resisting sugar is not just a matter of will power, however. I believe it is also linked to biochemistry and habit. When Carol came to see me some years ago she was in her early thirties and had been a member of over-eaters anonymous for seven years. During this time she had not touched refined sugar and yet she still craved it. Sugar craving is sugar addiction, no matter which way you look at it. She was still addicted to sugar because she was having to use her will-power NOT to eat any. However, she still evidently had marked fluctuations in her blood glucose levels.
Based on her symptoms, a glucose tolerance test was recommended and the results were proof enough. Carol’s blood glucose levels went up too high at first, into the mildly diabetic range, and then plummeted into the hypoglycaemic range. She felt dreadful while the test was being performed – and remember this was after seven years of avoiding sugar. We did not measure her insulin and adrenal hormones at the time, but needless to say the insulin mounted a delayed response to the sugar shock and then was produced in high amounts, resulting in the sudden drop in blood glucose, at which time the adrenals would have kicked in to increase the level again. Carol was in stage 1 or stage 2 of Insulin Resistance, but was certainly not a full-blown case. There were also adrenal issues.
Carol was not eating enough protein by any means, with none whatsoever at breakfast. In addition, her diet as a whole was relatively high in carbohydrates, though these had a relatively medium to low Glycemic Index. I addressed her lack of protein by getting her to eat high BV protein for breakfast, lunch and dinner. She continued to eat some carbohydrates as well, so it was by no means a low or no carbohydrate diet at all. When she got into the habit of eating the protein foods her craving virtually disappeared. Her will-power enabled her to implement the new programme, but it was the new programme that gave her new-found freedom from her cravings. She has a motto, which I often use myself, ‘discipline equals freedom’. The discipline to follow a programme allows you to derive the benefits from that programme.
What’s the difference between simple sugars and starches?
Glucose (aka dextrose) is the best-known simple sugar. Sugars composed of two monosaccharide units are called double sugars or disaccharides, and these are found extensively in nature. Sucrose, also known as table sugar, is the best-known double sugar. When you eat sucrose, the enzyme sucrase splits it into the simple sugars glucose and fructose, which are then quickly absorbed into the body. More complex sugars, or polysaccharides, contain links of many simple sugars. Starch, for instance, contains polysaccharides, and are therefore known as complex carbohydrates. Plant starch requires much greater digestion and hence is absorbed much more slowly than less complex sugars like sucrose or glucose. As a consequence, starchy vegetables have a medium to low Glycemic Index.
Starchy vegetables
Some examples of starchy vegetables are given below:
| Artichokes | Parsnip (cooked) |
| Beetroot | Potato |
| Carrots | Pumpkin |
| Corn | Sweet potato |
| Green peas | Turnip (cooked) |
| Leeks | Yam |
Cooking transforms more complex carbs into more simple carbs. This means that the GI of raw starches is almost always lower than cooked starches.
Fibre foods
Just as starch slows down digestion, so too does fibre. Fibre makes you feel more full, which helps reduce appetite and slows the release of sugar into the bloodstream. It feeds friendly bacteria, carries toxins out of the gut, so unwanted bugs are less able to flourish.
Essentially, there are two kinds of fibre, soluble and insoluble. Soluble fibre absorbs much more water, toxins and even cholesterol than insoluble fibre, and carries them all through the colon for elimination; insoluble fibre provides bulk but can irritate the gut lining, especially when eaten in excess. For example, oat bran, which is a rich source of soluble fibre, can lower cholesterol levels whereas wheat bran, a rich source of insoluble fibre, does not.
| Rich sources of soluble fibre | Rich sources of insoluble fibre |
| Soluble | Wheat bran |
| Fruits | |
| Vegetables | |
| Legumes | |
| Oats | |
| Pectin |
Legumes – which contain plenty of soluble fibre – are a particularly useful source of carbohydrate in the diet. This is because they have a low Glycemic Index and are very insulin-friendly. Unfortunately, some people
