What exactly is the GI Diet? GI stands for Glycaemic Index which is a scale from 0 - 100 which measures the speed at which glucose is absorbed from the intestine into the blood stream and the subsequent blood-glucose levels.
Virtually all carbohydrate foods are eventually broken down in the stomach and intestine to the simplest form of carbohydrate (known as monosaccharides) of which glucose is the principle one.
And since glucose is one of the most rapidly absorbed carbohydrates, the speed at which pure glucose is digested by the body and raises the level of glucose in the blood has been given a score of 100 on the GI. All other carbohydrate foods and drinks are measured against this.
Carbohydrate foods with a GI of 70 or over are considered to be high-GI foods; those with a number between 56 and 69 are considered to be medium GI foods and those with a GI number of 55 and below are low GI foods. Because fats and protein foods are not made up of glucose units, they have a GI of 0. However, they are required for a nutritionally balanced diet.
How do you lose weight by following the GI Diet? You lose weight by choosing low GI carbohydrates in preference to medium and high GI carbohydrates.
You see, low GI foods (also called complex or unrefined carbohydrate foods) raise glucose levels in the blood by a small amount and trigger low levels of insulin from the pancreas to remove any excess glucose from the blood. In contrast, high GI foods require large quantities of insulin to remove excess glucose from the blood so as to return blood-glucose levels to normal. This is a normal bodily reaction but the problem is that excess production of insulin (prompted by excess glucose in high GI foods) triggers other bodily systems to convert the glucose to body fat. Too much insulin also causes other reactions which make you feel hungry and urges you to eat more high-GI foods to get another glucose hit. Low GI foods, by contrast, keep the body feeling full and get it off the glucose hit rollercoaster.
What affects the GI of foods? Firstly, the amount of glucose in the carbohydrate is the crucial factor.
High GI foods contain a high proportion of glucose whereas low GI foods contain low amount of glucose or glucose in combination with other starches which take longer to digest. Adding low GI foods (such as beans, peas, lentils, whole fruits, oats, grains, multigrain breads, sweetcorn and pasta) to meals slows down the absorption of the whole meal.
Mixing a low-GI food with a high one also slows down the digestion and absorption of glucose. So, for example, by using grain or seed breads rather than white or brown bread because the hard coating of the seeds and grains slows down the digestive process of the flour and lowers the GI. The way food is prepared and cooked also impacts on the GI of the food. So, for example, small boiled potatoes have a lower GI than large mashed potatoes simply because the former takes a longer length of time to be digested.
Generally speaking if a food is peeled, mashed or processed before consumption it is easier for the digestive enzymes to attack it and break it down into glucose, therefore giving it a higher GI rating.
What are the origins of the GI diet? The scientific basis for the GI diet was established by Dr David Jenkins, professor of nutrition at the University of Toronto, some 25 years ago during his investigations into appropriate foods for diabetics.The length of time it has taken to become 'fashionable' is probably linked to the fact that the GI diet is based on a nutritional concept and it doesn't belong to anyone.
Spiralling rates of diabetes Type II and obesity have become a spur for many to look at how complex carbohydrate foods can provide clues to a weight loss and long term healthier diets.