Glycemic Index Information
What is the Glycemic index?
The Glycemic Index (GI) was developed in 1981. Dr David Jenkins was one of the key leaders and researchers in the development of the GI concept. The GI works by ranking foods containing carbohydrates on a scale from 0 to 100 according to their ability to raise blood glucose levels. Foods with a high GI of 70 or above on the scale, are rapidly digested and absorbed and this causes a distinct rise and fall, or spike in blood sugar (glucose) levels. Alternatively, low GI foods with a value of less than 55 on the scale, are broken down slowly and produce a more gradual rise in blood glucose levels. Due to their slower rate of digestion, low GI foods enable you to feel fuller for longer while sustaining your energy levels throughout the day. High GI foods get broken down quickly and are far less sustaining.
The 3 main GI categories are:
• Low (GI = less than 55)
• Intermediate (GI = 56 – 69)
• High (GI = 70 plus)
The Tony Ferguson Weightloss Program
The Tony Ferguson Weightloss Program is based on the low GI principle. It works by energy (Kilojoule/Calorie) and carbohydrate reduction. Two meals a day are replaced with Tony Ferguson Meal Replacement sachets and the third meal is a low carbohydrate, low GI meal option (protein and unlimited allowed vegetables). Allowed vegetables have a low carbohydrate content and low GI and may be consumed as often as desired throughout the day. People on the Program may also have 2 serves of low GI fruit and a few extras that are discussed with them upon registration on the Program.
Tony Ferguson sachets have a low GI of 22 and are nutritionally sound for weight loss as well as an ideal meal or snack option for those who would like to maintain their weight. The Tony Ferguson Cook Book was recently released. This book provides numerous low carbohydrate, low GI recipe suggestions for not only those on the weight loss program but also anyone that would like healthy meal ideas. It has many tips for eating and cooking healthily and also suggests a number of substitute options for favourite foods. For example, Notatoes, is a cauliflower substitute for mashed potatoes.
The Tony Ferguson Weightloss Program helps you to make better food choices for weight loss and wellness. Carbohydrates as a whole are not completely restricted rather the quantity consumed is reduced to enable weight loss. Eating low GI and limiting high GI carbohydrates is emphasized during both The Tony Ferguson Weightloss Program and The Tony Ferguson Maintenance Program (see next section for details). However some foods with low GI ranking are still not recommended while on the weight loss phase such as corn, pasta, peas and kidney beans because they are too high in low GI carbohydrates for effective weight loss on the Program.
The Tony Ferguson Maintenance Program
The Tony Ferguson Maintenance Program has been designed for people who reach their goal weight on the Tony Ferguson Weightloss Program or need to take a break from losing weight but want to maintain their current weight. The Tony Ferguson Maintenance Program is also based on the low GI way of eating and continues to recommend a small amount of protein at each meal and a low glycemic carbohydrate intake. The Program re-introduces food from all food groups but helps you learn which are the healthiest choices and about correct portion sizes. A food plan is worked out and customized to an individual’s weight, age and activity level with a Tony Ferguson consultant and can result in several previously limited foods being reintroduced in small amounts i.e. traditional rolled oats for breakfast or sweet potato for dinner.
The Glycemic Index and Health
Insulin is a hormone secreted by the pancreas (an organ in the body like the heart or liver) that allows glucose (sugar with a GI of 100) to enter the cells where it is used to sustain everyday activities. The continuous consumption of high GI foods creates a larger demand for insulin to reduce blood glucose spiking which can eventually exhaust the pancreas and in susceptible people combined with other factors may lead to insulin resistance and diabetes.
There are many proven health benefits associated with adopting a low GI way of eating and this is why the Tony Ferguson Weightloss Program follows this principle. In combination with other lifestyle factors, low GI eating has been shown to improve blood glucose levels in people suffering from diabetes, to help avoid the onset of heart disease as well as playing a key role in weight control by helping to manage appetite levels and delaying hunger.
Glycemic Index Foods
The Glycemic Index does not rank all foods. It can only be applied to foods with a reasonable carbohydrate content. Most vegetables (but not potatoes which are high in carbohydrates and have a high GI) and some fruits contain very little carbohydrates per serving, or have very low GI values. GI values vary for different fruits and starchy vegetables but most dairy products have a low GI. Foods such as cheddar cheese, oil, most meats, fish and eggs contain little to no carbohydrates and therefore do not have a GI ranking. The GI refers to all carbohydrates and sugars, for example lactose (a milk sugar) has a low GI rating of 46 and fructose has a rating of 19. The GI also applies to any diet that contains carbohydrates i.e. a vegetarian or lactose free diet.
The GI can vary between different varieties of a food. For example multigrain bread has a lower GI than wholemeal, white and Lebanese bread.
There are several factors that can influence a food’s GI such as fat content. For example, potatoes have a higher GI than chips as chips have added fat. However the fat content of chips make them an unhealthy option. Another example is chocolate, some chocolate bars have a low GI due to their high fat content and again the low GI rating does not make them a healthy choice. Other factors that can affect the GI rating of a food are ripeness and processing which can increase the GI. For example, the longer you cook pasta, the higher its GI will be, to an extent. Some foods are naturally high in acidity e.g. berries. Acidity helps lower the GI rating.
There are also methods of reducing the effect of high GI foods. For example, by eating a low GI food with a high GI food in the same total quantity that would normally be consumed, the effect on blood glucose will be lowered somewhat by the low GI food. However doubling up on either low or high GI food will raise blood glucose higher than a single serve and will take longer for levels to return to normal. So a food having a low GI does not mean you can eat more!
Here are a few examples of different types of foods and their GI ranking;
Note: Foods with little or no carbohydrate content do not have a GI value. They would be considered low if to be categorized. These foods are usually defined by other nutritional properties e.g. fibre, protein or fat.
| Food | GI Rating | GI Category |
| Cereal | ||
| Cornflakes | 77 | High |
| Coco Pops | 77 | High |
|
Guardian |
37 | Low |
| Fruit loops | 69 | Intermediate - borderline high |
| Fruit | ||
| Banana | 52 | Low |
| Strawberries | 40 | Low |
| Watermelon | 77 | High |
| Apple | 38 | Low |
| Peach | 42 | Low |
| Grapes | 53 | Low |
| Oranges | 42 | Low |
| Lemons | - | Little or no carbohydrates |
| Prunes | 29 | Low |
| High Carbohydrate Foods | ||
| Pasta (wheat) | 40-50 (varies) | Low |
| Pretzels | 83 | High |
| Rice Crackers | 91 | High |
| Jasmine Rce | 89-109* | High |
| White Bread | 70-80 | High |
| Beans | ||
| Kidney beans | 36 | Low |
| Broad beans | 79 | High |
| Meat/Eggs | ||
| Chicken | - | Little or no carbohydrates |
| Steak | - | Little or no carbohydrates |
| Lamb | - | Little or no carohydrates |
| Pork | - | Little or no carbohydrates |
| Eggs | - | Little or no carbohydrates |
| Vegetables | ||
| Spinach | - | Little or no carbohydrates |
| Pumpkin | 75 | High |
| Potato | 70-101* | High |
| Tomato | - | Little or no carbohydrates |
| Sweet Potato | 46 | Low |
| Parsnips | 97 | High |
| Zucchini | - | Little or no carbohydrates |
| Liquids | ||
| A glass of milk | 27-34 | Low - high carbohydrates |
| A glass of fruit juice | 37-53 | Low - high carbohydrates |
| Water | - | Little or no carbohydrates |
| Oil | - | Little or no carbohydrates |
*Foods that digest faster than Glucose have a GI value higher than 100
Glycemic Loading
Glycemic load or GL combines both the quality (GI) and quantity of a carbohydrate in one ‘number’. It’s the best way to predict blood glucose values of different types and amounts of food. GL is best described as the amount of carbohydrate in a food ‘adjusted’ for its glycemic potency.
The formula to work out a food’s GL is:
GL = (GI x the amount of carbohydrate) divided by 100.
For example a food with a GI of 40 which contains 15 grams of carbohydrate has a GL of:
(40 x 15)/100 = 6 g
Despite the usefulness of the GL, the mistake of only choosing low GL foods should not be made rather both the GI and GL should be considered. This is because foods that may be high in fat may have a low GL due to a low carbohydrate content. This also affects the GI value but the GI can be more useful when wanting to compare similar foods to help make better choices without a GL value present.
GIycemic Index Testing
The GI of different foods must be measured using valid scientific methods. It cannot be guessed by looking at the composition or the aroma of a food. Currently, only a few nutrition research groups around the world provide a legitimate testing service. Professor Jennie Brand-Miller at the Human Nutrition Unit, Sydney University has been at the forefront of Glycemic Index research for over a decade, and her research group has determined the GI values of more than 400 foods.
The GI value of a food is determined by feeding 10 or more healthy people a portion of the test food containing 50 grams of digestible (available) carbohydrate and then measuring the effect on their blood glucose levels over the following two hours. This is done on 2 – 3 separate occasions and an average value is calculated.
On another occasion, the same 10 people consume an equal-carbohydrate portion of glucose (the reference food) and their two-hour blood glucose response is also measured.
A GI value for the test food is then calculated for each person by dividing their response to the test food by their response to glucose (reference food). The final GI value for the test food is the average GI value for the 10 people, with the result then multiplied by 100, to turn it into a percentage.
Last updated 08 September 2009
