Low GI (glycemic index) diets come in many shapes and sizes. Nevertheless, all low GI diets are based on the same principle of balancing blood sugar. The foods which are restricted on low GI diets are those which cause your blood sugar and insulin levels to rise fast and high. This rise is measured using a scale called the glycemic index (GI for short), which is how Low GI diets got their name.
It is only carbohydrates which affect blood sugar and insulin levels to any significant degree. Foods containing high amounts of carbohydrate include flour and sugar, potatoes, rice, corn and other grains and the many foods made with them. In general, the GI of a carbohydrate food becomes higher the more highly processed it is. So for instance, mashed potatoes have a higher GI than boiled potatoes, and white bread made with highly refined white flour has a higher GI than whole grain bread. Lesser amounts of carbohydrate are found in peas and beans, nuts and seeds, fruits and vegetables and milk and milk products.
Carbohydrate-free foods (eg fats and proteins such as meat, poultry, fish and pure protein powders) and foods containing so little carbohydrate that their glycemic effect is not measurable (eg cheese and eggs) are not limited from the glycemic index point of view. However, there may be other reasons to avoid the food - for instance if it is a trans fat. This is explained further in
"Why Can't I Lose Weight - the real reasons diets fail and what to do about it".
Low GI diets are similar in many ways to low carb diets, and understanding the difference between them can be confusing. This is explained in detail in The Easy Guide to Low Carb & Low GI Diets, which comes as a bonus with the
Low Carb / Low GI Cookbook.
The basic rules of any low GI diet plan are to: Reduce intake of concentrated sugars and starches
Swap highly refined flour products such as white bread, low-fibre breakfast cereals and quick-cooking starches for grain products produced using traditional methods (eg wholewheat pasta, stone-ground flour, old-fashioned oatmeal)
Choose whole grains such as brown rice, buckwheat and quinoa instead of potatoes and white rice
Increase intake of peas and beans, nuts and seeds and most vegetables and fruits
Many low GI diets also advocate choosing lean meat and low fat dairy products in order to keep intake of saturated fat low.
Not all low GI plans are specifically aimed at weight loss. Some are simply aimed at healthy eating, which is important for your long term health even if you don't have any weight to lose. The foods that cause the highest rises in blood sugar and insulin levels are bad for you in general, as they tend to be highly processed. This strips them of the vitamins, minerals, enzymes and fibre that your body needs in order to be healthy. By eating the low GI way, you are reducing your consumption of unhealthy foods such as white flour, sugar and white rice and replacing them with nutrient-dense, fibre-rich whole grains and other unprocessed foods such as fruits and vegetables.
The main difference between a 'healthy eating' low GI plan and a 'weight reducing' low GI plan is the degree to which carbohydrates are restricted. Just switching to a lower GI way of eating than you are currently following may be enough to produce weight loss, but this depends on your individual metabolism and how sensitive you are to carbohydrates. For many people, losing weight on a low GI diet means choosing one that restricts carbohydrate foods quite severely.
Here we are assuming that you are considering a low GI diet because you want to achieve weight loss as well as better health. We have created two methods of following a low GI diet so that you can choose the one which best suits the way you like to do things. The first will suit you if you prefer to approach things in a very exact and detailed way. On the other hand, if you are the kind of person who prefers a less detailed approach, then our second method may suit you best.
Method 1 - the detailed approach
If you wish to follow a low GI diet in a very exact and detailed way, you will need to plan your menus by looking up the GI ratings of all the carbohydrate foods you plan to eat at each meal.
It is probably best to start your diet by eating only those carbohydrate foods which rank Low on the GI scale. If your individual metabolism does not require such a strict approach, you could choose Low GI foods most of the time and Medium GI foods some of the time. If you are very lucky, you may even be able to add High GI foods occasionally and still lose weight.
GI rating ranges
Most GI rating tables give values on a scale of 1 to 100. Deciding at which points on the scale a Low GI score becomes a Medium one, and a Medium one a High one can only be arbitrary - the difference in glycemic effect of two foods with scores either side of a category limit will not be any greater than the difference between two foods that rank next to each other in the same category. The Low, Medium and High categories can therefore only be an approximate guide.
The following categories are the most common among low GI plans: Low - 0 to 55
Medium - 56 to 70
High - 71 to 100
See our GI and GL Handy Reference Tables for a useful list of GI and GL ratings for the most common foods, which comes as a bonus with the
Low Carb / Low GI Cookbook.
Points to remember
Proteins (such as meat, poultry, fish, cheese, eggs) and fats are free foods as far as GI is concerned. You can eat these in normal portions. An adequate quantity of protein is essential for health, and so is fat (but there are 'good' fats and 'bad' fats. These are explained in
"Why Can't I Lose Weight - the real reasons diets fail and what to do about it".
Remember that your health depends upon an adequate intake of vitamins, minerals, enzymes and fibre. Eating plenty of vegetables and salads in addition to protein foods and fats is an important way of ensuring you get the wide range of nutrients your body needs. Fruits are also valuable providers of vitamins, minerals and fibre, but experts confirm that vegetables contain just as wide a range of nutrients as fruits do, if you cannot tolerate fruits.
Keep in mind that some foods are a ready-made mixture of carbohydrates and protein and often, fats too (eg nuts and seeds, peas and beans, grains, milk)
It is the overall glycemic effect of your meals that counts. When you make a meal that contains foods from different GI categories, the overall glycemic effect will be the average of the ratings for the individual foods. So coupling a High GI food with a Low GI food will have the approximate effect on your blood sugar/insulin of a Medium GI food. For instance, a baked potato (High) eaten with baked beans (Low) will give an overall Medium GI effect. Similarly, pour milk (Low) on cornflakes (High) to achieve a Medium GI effect.
Don't forget that you can get an even better GI-reducing effect by coupling a carbohydrate food with a carbohydrate-free food - in other words, eating protein and/or fat with your carbohydrate. For instance, you could accompany a potato with a portion of GI-free food such as meat or fish, or put olive oil on your rice salad to bring down the overall glycemic effect.
The GI rating for a food remains the same, however much of it you eat in your meal. But this does not mean you can have a double size portion - if you do, the increased quantity will still cause a higher glycemic effect than you would get if you ate a normal portion.
See below for
more tools to help you.
Method 2 - the approximate approach
If you prefer a less detailed way of planning your menus the low GI way, you can simply make your carbohydrate choices according to the 'Eat more', 'Cut out/severely restrict' and 'Swap' lists below.
If you don't see a particular food listed, and it is a salad or non-starchy vegetable, you can be sure it's in the 'Eat more' category. If it's white bread, white rice, sugary drinks, cakes, biscuits/cookies, pastries, desserts or sweets, then you should assume it is in the 'Cut out/severely restrict' category.
Keep in mind that foods marked * such as whole grains, starchy vegetables and some fruits are in between on the GI scale - treat them cautiously until you know you can include them in your diet and still lose weight.
Points to remember
Proteins (such as meat, poultry, fish, cheese, eggs) and fats are free foods as far as GI is concerned. You can eat these in normal portions. An adequate quantity of protein is essential for health, and so is fat (but there are 'good' fats and 'bad' fats. These are explained in
"Why Can't I Lose Weight - the real reasons diets fail and what to do about it". Keep in mind that some foods are a ready-made mixture of carbohydrates and protein and often, fats too (eg nuts and seeds, peas and beans, grains, milk)
Remember that your health depends upon an adequate intake of vitamins, minerals, enzymes and fibre. Eating plenty of vegetables and salads in addition to protein foods and fats is an important way of ensuring you get the wide range of nutrients your body needs. Fruits are also valuable providers of vitamins, minerals and fibre, but experts confirm that vegetables contain just as wide a range of nutrients as fruits do, if you cannot tolerate fruits.
It is the overall glycemic effect of your meals that counts. So coupling a 'Cut out/severely restrict' food with an 'Eat more' food will reduce the overall effect on your blood sugar/insulin of the High GI food.
Don't forget that you can get an even better GI-reducing effect by coupling a carbohydrate food with a carbohydrate-free food - in other words, eating protein and/or fat with your carbohydrate. For instance, you could accompany a potato with a portion of GI-free food such as meat or fish, or put olive oil on your rice salad to bring down the overall glycemic effect.
The GI rating for a food remains the same, however much of it you eat in your meal. But this does not mean you can have a double size portion - if you do, the increased quantity will still cause a higher glycemic effect than you would get if you ate a normal portion.
Choosing your carbohydrate foods by the approximate method
Eat more of the following carbohydrate foods:
- All green vegetables including broccoli, courgettes/zucchini, green beans, kale
- All white vegetables including cauliflower, white cabbage, mushrooms, radishes
- All salad vegetables such as lettuce, cucumber, peppers, tomatoes
- Whole fruits such as apples, cherries, grapefruit, pears, plums, oranges, strawberries, peaches
- Pulses such as lentils, chickpeas and dried beans
- Seeds such as linseeds/flax, pumpkin, sunflower, sesame and hemp
- Nuts such as almonds, brazils, walnuts, pine nuts, macadamias and peanuts
- Plain yoghurt
- High fibre, unsweetened cereals such as All Bran and muesli
- High fibre, whole grain bread
- Sweet potatoes
- Whole wheat pasta *
- Brown basmati rice, buckwheat grains, quinoa, bulgur wheat, pearl barley *
* whole grains, starchy vegetables and some fruits are in between on the GI scale - treat them cautiously until you know you can include them in your diet and still lose weight
Cut out or severely restrict the following carbohydrate foods:
- Starchy vegetables such as parsnips and cooked carrots
- Ripe bananas
- Fruit yoghurts and desserts high in sugar such as imitation mousse
- Fruit juices
- Dried figs, dates
- White bread, baguettes, bagels
- Cream crackers, white rice cakes
- Iced cakes and pastries, filled biscuits/cookies, doughnuts
- Scones, crumpets, waffles
- Sweet pies
- Fruit canned in syrup
- Breakfast cereals containing sugar
- Baked and mashed potatoes, chips/fries
- White rice
- Corn and rice pasta
- Pizza
- Popcorn
- High sugar jams/jelly
- Crisps/chips and other potato- and corn-based snacks
- Fruit drinks containing added sugar
- Fizzy drinks containing sugar
- Sweets/sugar candy and chocolate bars/chocolate candy
- Thickened soups
- Table sugar
- Ice cream containing glucose syrup or high levels of other sugars
Swap these higher GI foods...... for these lower GI foods
- Old-fashioned oatmeal porridge
- Cornflakes or rice krispies
- Whole grain / granary bread sandwich
- Basmati rice, wholegrain rice or sweet potato
- Basmati rice or wholegrain rice
- Small handful of nuts, or raw vegetable sticks with cheese
- Cola or other regular fizzy drink
- Artificially sweetened fizzy drink (or better still, water)
- Apple or pear or other low GI fruit
- Fruit-filled chocolate bar
- Plain dark chocolate (70% or more cocoa solids)
- Jam/jelly or marmalade on toast
- Curry with chickpeas or lentils
- Fun-size Snickers bar, a few chocolate peanuts or dark chocolate
More tools to help you
To make it even easier for you to achieve success with your diet, we have developed the following tools to help you:
Understanding more about low GI, low GL and low carb diets and deciding which is best for you
The Easy Guide to Low Carb & Low GI Diets is available as a bonus with the
Low Carb / Low GI Cookbook.
Low GI menu plans
Check out our free
Low GI menu plans.
Finding low GI recipes
You don't necessarily have to look for 'low GI' recipes to be sure that a recipe is OK for you to use on your low GI diet. All very low carb recipes are also suitable for low GI diets - if a food is very low in carbs, it cannot have an appreciable glycemic effect. All recipes in
The Low Carb / Low GI Cookbook are suitable for low GI diets.
If you are not losing weight on your low GI plan
Keep in mind that many people have a low level of tolerance for carbohydrates, even the 'good' or Low to Medium GI ones. If your low GI plan allows a level of carbs which is too high for you as an individual, this may stop you losing weight. If this happens, try substituting the higher carb items for lower carb foods. For instance, instead of wholegrain bread, substitute bread made with flours made from healthy, low carb flax seeds, almonds, soya beans, hemp or sesame seeds instead of high carb wheat, rye or corn. Delicious and easy to make breads made with these low carb, super-healthy ingredients can be found in
The Low Carb / Low GI Cookbook. There are other mechanisms at work which can also prevent you from losing weight, no matter which diet you try. These are explained in
"Why Can't I Lose Weight - the real reasons diets fail and what to do about it".
