Q I’ve been trying to lose weight by following a low glycaemic index (GI) diet. I’ve heard that foods with a low GI should keep me feeling fuller for longer but they don’t, nor am I losing weight.
A You’re not the only one to be disappointed with the weight-loss promises of low-GI diets. Now the subject of many diet books, the low-GI diet may be nutritionally balanced but it’s not necessarily a panacea for weight problems. Foods with a lower GI are generally more nutritious than those with a higher GI – whole grains, for example, provide more nutrients, fibre and phytochemicals than refined carbohydrate equivalents – but to lose weight you still need to consume fewer calories than you burn. In other words, calories still count even if you are eating a low-GI diet.
There have been no long-term studies but, of the short term research to date, only about half have found that foods with a low GI reduce hunger, increase satiety (feelings of fullness) or reduce overall food intake; whereas no difference in satiety or food intake was found in the other half. A study published in The American Journal
of Clinical Nutrition in 2004 found that weight loss on a low-GI
diet was no different to that on a high-GI diet.
In theory, a low-GI diet should be filling and satisfying
because many foods with a low GI are high in fibre and take longer to digest, helping to curb your appetite. In practice, however, it’s quite easy to unwittingly load up on calories. Muesli (GI 49), boiled (as opposed to baked) potatoes (GI 50), and spaghetti (GI 48) are foods with a low GI but are relatively high in calories. Even milk chocolate has a respectable GI (43) but provides a whopping 240kcal per 45g bar.
Clearly a low-GI rating isn’t a licence to eat freely; you still have to keep an
eye on portion sizes. The answer is to eat higher-calorie or carb-dense foods with a low GI (cereals, breads, full-fat dairy products, desserts, and confectionery) in moderation and fill up instead on fibre-rich foods with a low GI and a high water content (fresh fruits, vegetables, and salads).
— Anita Bean, Nutrition Editor