The glycemic index is a system that ranks carbohydrate foods based on their effect on blood sugar levels. The Low GI Diet is based on eating carbohydrates with a low glycemic index. These foods cause small fluctuations rather than large spikes in blood sugar and insulin levels, producing steadier energy levels and enabling better weight control.
The Glycemic Index
Initially developed to help diabetics manage their blood sugar, the glycemic index assigns a ranking from 1 to 100 to carbohydrate foods, with pure glucose, which ranks 100, as the reference point. The GI measures how quickly a carbohydrate food is digested, converted into glucose, and then raises a person's blood sugar level. During digestion, carbohydrates break down into glucose, causing a temporary spike in blood sugar levels. A high glycemic index food, such as white bread, will cause a rapid high spike then drop in blood sugar. A low glycemic index food, like whole oats, is digested more slowly, and produces a lower, slower, and more gentle change in blood sugar. In the Glycemic Index ranking system, low GI foods are ranked 55 or under, moderate GI foods are 56-69, and high GI foods are ranked 70 and above. (See References 1 and 2)
The Low GI Diet
The Low GI Diet is based on eating carbohydrate foods with a low GI ranking. The rationale is that lower GI foods, which are more slowly digested and absorbed, will cause a slower rise in insulin and blood sugar levels. High GI foods, which are digested and absorbed more quickly, cause more dramatic fluctuations, promoting fat storage and intensifying hunger. Because of their low impact on blood sugar, foods in the Low GI Diet reduce insulin levels and resistance, assist with appetite control, delay hunger, and help with weight control. (See Reference 2)
How To Follow A Low GI Diet
It is not necessary to count numbers on the Low GI Diet but rather to learn how to replace rapidly digested and absorbed high GI foods with the more slowly digested and absorbed low GI foods. Higher GI foods are not forbidden but should be eaten together with low GI foods. The goal is to eat low GI foods with at least two meals each day and to try to eat them with each meal. Some basic recommendations for easy switches are to: eat a lot of fruit and vegetables except for potatoes; eat salad with vinaigrette dressing; eat barley, bran, and oat cereals; use varieties of rice other than white, instant, or glutinous; and to eat sourdough, stone ground, or whole grain bread. According to Harvard's Nutrition Source, other factors also affect the glycemic index and need to be taken into consideration on a low GI diet. Processed refined foods with the bran and germ removed and finely ground more quickly digested grains have a higher GI than whole or more coarsely ground grains. Some types of starch, like the kind found in potatoes, is easier to break down into sugar molecules and has greater blood sugar impact. More fibrous foods break down more slowly and deliver less sugar while ripe fruit and vegetables tend have more sugar a higher GI. A meal with higher fat or acid content generally slows down glucose conversion and blood sugar impact.
What To Eat On A Low GI Diet
It is not necessary to memorize the GI value of every food. Eating fruits and vegetables every day, except for potatoes, is important. It is important to learn the GI of the most frequently eaten major carbohydrate foods including bread, rice, pasta, and cereal, and then choose the ones that have lower rather than higher GI rankings. Eat only small portions of high GI foods and eat them along with a low GI food. Depending on variety, processing, and preparation, a particular food may be either low, moderate, or high GI. For example, brown rice (GI 50) and white long grain rice (GI 50) are both low glycemic foods. Basmati rice (GI 58) and wild rice (GI 57) are medium GI foods, while instant white rice (GI 87), glutinous rice (GI 86), and short grain white rice (GI 83) are high GI foods. Some foods may have a low GI ranking but may not be rich in nutrients. The intent is to choose high-quality, nutrient dense, low GI foods.
Benefits Of A Low GI Diet
Low GI foods have health benefits as a result of their slow digestion and absorption. The gradual rises they produce in blood sugar and insulin keep energy levels balanced and a longer feeling of fullness between meals. When following a low GI diet, Type 1 and type 2 diabetics have shown improved glucose and lipid levels and weight loss. The high glucose levels, or glucose spikes, produced after eating high GI foods, prompt the release of too much insulin and have been associated with increased risk for diabetes, heart disease, and overweight. Avoiding blood glucose spikes by following a low GI diet means a much steadier level of energy and a reduced risk of heart and other chronic diseases associated with blood sugar fluctuations. Some studies, however, have found little effect of the glycemic index on weight or health. (See References 1 and 2)
