Total calorie intake is a key factor in weight loss, but making the right food choices makes it much easier to keep calorie intake low. Although fat is very calorie dense, processed carbohydrates can sabotage weight loss diets because they digest so quickly. Low GI foods digest more slowly and are therefore a better choice for weight control.
What GI is
GI (Glycaemic Index) is a measure of how quickly different carbohydrates convert to glucose in the body. The original purpose of GI ratings was to help diabetics control blood glucose, but they can also be helpful in weight control.
All carbs end up as glucose in our bodies. The important point for weight control is how long this takes. If they break down quickly (high GI), we get a blood glucose high. The glucose then has to be removed from the blood and stored as fat and we are soon hungry again. If carbs break down slowly (low GI), there is a slow glucose release, no need for fat storage and we stay full longer.
So, if we choose low GI foods, this helps to control weight. The glycemic index ratings tell us how quickly carbs release sugar. GI tables usually group foods into 3 sections – high, medium and low GI. Obviously, it’s best to avoid the high and medium foods as much as possible.
How to choose low GI foods.
GI is not a measurement like calories – it’s a comparison. The GI of glucose is set at 100 (very high) and everything else has a value compared to this. But basically, high GI foods are unhelpful for weight control and low GI foods are good. Examples of low GI choices are:
- Wholegrains. These contain a lot of fibre, so glucose is released slowly. Processing removes most of the fibre from white bread, pasta and rice and so they digest quickly. If you don’t like the brown versions, try mixing just a little in with white – this will help to slow down the glucose release.
- If you like to snack on fruit, you’ll find that some fruits are naturally lower GI than others – apples are a good choice, but grapes are quite high GI
- Sweets are very high and the sugar will cause a real blood glucose spike – chocolate is lower GI and has more nutritional value, so is a better choice even though it contains fat
There are lots GI tables available online and in books but unfortunately, they don’t all give the same information about the GI values of foods. Most of them give roughly the same values, but you might find small differences from one table to the next. Professor Jennie Brand-Miller at the University of Sydney developed the GI system, so this University of Sydney website is a reliable resource. For a printable PDF GI chart, also see these links:
As a basic rule of thumb: avoid white carbs, sugar and sweets and foods with a high added sugar content.
See these posts to learn more about eating a healthy diet for weight loss: