The GI Diet:

Written by: Daisy Whitbread BSc (Hons) MSc DipION MBANT ANutr

GI stands for glycaemic index. It is a system for measuring the speed at which the digestive system breaks down carbohydrate foods into glucose, the body’s source of energy. Foods are ranked from 1-100, glucose has the maximum score of 100 and all other carbohydrates are measured against this.

High GI carbohydrates, such as white bread or cornflakes, are digested rapidly by the body, causing an immediate and sharp rise in blood sugar levels. Low GI carbohydrates on the other hand, such as oats or granary bread, take longer to digest and therefore release their sugar slowly and gradually into the bloodstream.

Insulin is a hormone secreted by the pancreas, which regulates blood sugar levels, and controlling insulin levels is key to the GI diet. Insulin’s job is to regulate blood sugar levels by removing any excess glucose from the blood and storing it as fat. It also acts as a guardian of fat stores, encouraging the body to maintain its precious stores.

Eating high-GI carbohydrates and the resultant increase in blood sugar, causes large amounts of insulin to be secreted. Eating mostly low-GI foods will result in less insulin production and therefore less fat storage.

High insulin levels in the body create a biochemical environment that encourages fat storage.

Blood sugar and insulin levels also affect appetite regulation. When levels are balanced we feel full for longer and our mood and energy levels are more consistent. However, the highs and lows of blood sugar and insulin produced by eating high-GI carbohydrates lead to increased appetite, sugar cravings and fluctuations in mood and energy levels.

The GI diet therefore is based on eating mostly low-GI carbohydrates and avoiding high-GI ones.

•           Any processing of foods will raise the GI, as processing is basically carrying out some of the digestion outside of the body, before you even eat the food.

•           Although GI only applies to carbohydrates, it is also influenced by protein and fat, both of which slow down carbohydrate digestion, reducing the overall GI of a meal.

Advantages of the GI Diet

•               Creates a biochemical environment that encourages fat burning
•               Reduced food cravings
•               No need to rely on will power
•               Improved energy
•               More balanced mood
•               Don’t feel hungry
•               Can be maintained for life
•               Reduced risk of heart disease and diabetes
•               No cutting out of whole food groups
•               Can still eat out and enjoy food
•               No weighing, measuring, calorie counting
•               Scientifically proven


The Rules        

           Avoid high-GI carbohydrates

For example white bread, white rice, cornflakes, crispbreads. Replace with low-GI ones such as granary bread, brown basmati rice and oats.

           Eat protein

With every meal as protein lowers the overall GI of a meal. Lean protein sources such as fish, seafood, eggs, beans, tofu, lean meat, chicken, turkey and low fat dairy should be chosen.

             Increase fibre intake

Fibre slows digestion and therefore the GI of foods. It keeps you feeling full for longer. Research shows that doubling fibre intake can help reduce calorie intake by up to 20% without any other dietary alterations.

           Eat the right kind of fat

Plant oils such as those from nuts, seeds and olive oil plus oily fish should be chosen in favour of saturated animal fats. These fats are metabolised more quickly by the body than saturated fats, they increase the speed of carbohydrate metabolism, helping to burn-up carbohydrate calories, and they can help to balance mood.

           Eat regularly

Eat 3 meals plus 3 snacks each day to keep blood sugar balanced. Never miss a meal!

           Avoid/Limit caffeine

Avoid if possible or limit to 1 coffee or 2 teas per day. Avoid cola/energy drinks completely. Caffeine can cause insulin levels to rise.

           Stay hydrated

Thirst signals can be mistaken for hunger, drink 2 litres of water and herbal teas each day.

           Eat slowly

Take your time over meals and chew food thoroughly. This allows enough time for messages to travel from your stomach to your brain telling it when you have eaten enough.

           Sleep well

Lack of sleep causes the release of a hormone which increases appetite. It can also raise insulin levels in the morning. Aim for 7-8 hours.


Stress increases production of the hormone cortisol, which increases appetite and fat storage. Try warm baths, yoga, meditation, calming music.


Typical Menu

Breakfast: Scrambled eggs on granary toast
Snack: An apple
Lunch: Wholemeal pitta filled with salmon and watercress, natural yoghurt with a pear.
Snack: An oatcake with peanut butter
Dinner: Spaghetti bolognaise, fresh berry salad
Snack: A small bunch of grapes or a glass of warm skimmed/soya/almond milk