Margot Brennan, Irish Nutrition and Dietetics Institute: "The Glycaemic Index is nothing new to dieticians. We have been using it for years, particularly with diabetics and more recently for weight management.
It involves choosing healthy foods and poses no health hazards. There is a lot of research showing that it increases satiety so that people adhere better to the diet. The foods tend to be high in fibre and high in anti-oxidants.
It does help to lower cholesterol and triglyceride levels and therefore can reduce the risk of coronary heart disease.
A GI diet is generally a healthy eating diet. However, there are certain things we need to consider because a low GI diet is not necessary a low calorie diet. So on its own, you won't lose weight, however, including it as part of an overall healthy lifestyle is very useful.
Some presentations of the GI diet make it seem impractical by including foods that are difficult to find in the shops (such as seeds, pumpernickel bread). This need not be the case. The other major difficulty with it is that the GI of certain foods vary, depending on who did the analysis. However, that said, they generally fall into the same category (ie high, medium or low GI foods). Also, we don't eat foods in isolation and others factors influence the GI of food (eg putting butter on bread lowers the GI of bread and baked potatoes are high GI foods yet if you eat the skins, this lowers the GI). Overall, there is need for more research but it is a diet that we are using and watching carefully.
Dr Patrick Wall, professor of food safety at UCD Centre for Food Safety and Medical Epidemiologist with UCD Institute for the Study of Social Change: Our health is our greatest asset and food as the fuel for the body is fundamental to good health. Therefore it behoves us all to think about what we are ingesting. At the end of every day we should ask ourselves the question "what did I do for my health today?" If we can answer, that we ate a healthy diet and took a bit of exercise we're half way there, if we can add that we didn't smoke, or overdo the alcohol, then we are almost the full distance.
Thinking about what we are eating is the first step on the journey to good health. The glycaemic index scores food on a scale on 1 to 100 according to the extent to which these foods raise blood sugar levels after eating.
Foods that are rapidly absorbed can result in very high blood sugar, the body responds by producing insulin to lower the level which often dips too much sending a signal to the brain to eat something to bring the level up, the brain then triggers the feeling of hunger and "cravings" that will challenge the most determined dieter. The cycle of fluctuating blood sugar level that results from eating too much high index foods is unhealthy, therefore the trick is to eat foods that release sugar much slower and keep the blood sugar levels steady.
The GI value tells us how rapidly a particular carbohydrate turns into sugar but it does not tell us how much of that carbohydrate is in a serving of a particular food. We need to know both things to assess a food's effect on our blood sugar. A more helpful measure is the "glycaemic load" which is the amount of available carbohydrate (carbohydrate minus fibre) in grams, multiplied by the GI value and divided by 100.
If we just judge foods on the basis of the GI value we would exclude a lot of food that is good for us. For example the carbohydrate in watermelon has a high GI value but there isn't a lot of it so watermelon's glycaemic load in relatively low. Many vegetables such as carrots have quite high GI values but don't contain much carbohydrate so have a low glycaemic load and have little effect on blood sugar. The lower the load the longer we will stay satisfied and the less we will eat.
Following any kind of diet requires discipline and willpower, two commodities often in short supply so a regime that is simple to adhere to and compatible with a normal lifestyle is more likely to succeed. Cutting down on sweets, biscuits, cakes and other confectionary and taking a bit of exercise daily will bring you most of the way and there is no need to buy any diet books.
Professor Mike Gibney, Department of Clinical Medicine, Trinity College, Dublin: One thing that has always bothered me about the Glycaemic Index as a way of rating foods is that you don't eat certain foods in isolation but you eat a mixture of foods in a meal. If you think that white bread has a different GI with or without butter, how can someone work out the GI of a meal with soup, bread, meat in a sauce, vegetables, rice and a glass of wine.
The fundamental thing about losing weight is that you need to expend more energy than you put into your body. So you can gain weight by eating large quantities of low GI foods if your energy intake exceeds your output. Some people say that you will feel fuller with low GI foods but I'm not convinced of that, especially if you consider how the GI of foods can be changed completely depending on what other foods you are eating. Dolly Parton once replied to Michael Parkinson's question about her figure on his BBC show by saying 'honey, if you want to lose weight, get your head out of the slop bucket'. I think you can't beat that for a piece of advice for those who want to lose weight.