The glycaemic index (GI), represents the effect a certain food has on insulin within the body, a low score (<70) is seen as favourable in terms of health, particularly for the prevention of obesity, type 2 diabetes and CVD. The GI of a given food is affected by a number of factors.
- The type of carbohydrate, (glucose, 138: Maltose 105; Saccharose 75; Fructose, 30)
- The fat and protein content of the food, (A slower rate of gastric emptying lowers GI)
- GI is affected by acidic, by virtue of acidity slowing gastric emptying, adding citric acid or fruits will therefore lower GI
- A higher water content will lower GI
- The presence of viscous soluble fibre, the ripeness, cooking or processing that makes food more digestible
- Presence of insoluble fibre found in whole ‘intact’ grains
Within the westernised diet, most carbohydrate sources are highly refined cereal and potato products, these tend to have higher GI values, which is linked to the increase in type 2 diabetes, cardiovascular disease and metabolic risk.
Low GI diets may contribute to weight loss, i) by virtue of reducing overall calorie intake: ii) stored glycogen will release water when utilised in energy breakdown, both. Of which would reduce risk of metabolic syndrome. Food choices will need to be limited severely to reduce overall GI, highly processed foods will not be as prominent leading to this reduction in calories. Protein will become the main focus of a low GI diet as it will increase gastric emptying and situating properties, also allowing weight loss to occur. Rapid weight loss will occur, with up to 1-2kg realistically within the first week just from liver and muscle glycogen and subsequent water.
| Wholegrain Bread | Mulitgrain Bread | Rye Bread |
| Rolled Oats | All Bran | Sourdough Bread |
| Apples | Strawberries | Peaches |
| Plums | Broccoli | Cauliflower |
| Sweet Potato | Lentils | Baked Beans |
| Butter Beans | Pasta | Rice Noodles |
| Brown Rice | Quinoa | Milk |
| Cheese | Custard | Cheese |
| Nut milks | Pear | Celery |
| Chickpea | Kidney Beans | Basmati Rice |
| Buckwheat | Yoghurt | Apricots |
Heres a list of foods that are generally lower GI, you’ll notice that they are non-refined foods. Most are whole-foods commonly found in protocols used for body fat loss.
Low GI diets have also been used for, women post-menopausal age, women with PCOS and type 2 diabetics. However, this is beyond the scope of this post.
Important things to consider:
Long term compliance to a low-GI diet may induce favourable metabolic effects.
A diet high in fruits and vegetables, whole grains and low-fat dairy products are important for weight loss.
Reduced hyperinsulinemia associated with a low-GI diet may reduce CVD risk through effects on oxidative stress, blood pressure, serum lipids, coagulation factors, inflammatory mediators, endothelial function and thrombolytic function
Based on associations between these metabolic parameters and risk of disease, further controlled studies on low-GI diet and metabolic disease are needed
Data from long term clinical trials on the metabolic effects on different diets are needed in this area.