I think conventional nutritional advice (as dispensed by our Governments and health professionals) puts generally too much emphasis on carbohydrate, including forms of this that tend to cause considerable disruption in blood sugar and insulin levels. The consumption of so-called ‘high glycaemic index’ (high GI) carbohydrates have been linked with an increase in risk of all manner of ills including weight gain, type 2 diabetes, cardiovascular disease and gallbladder disease. So, as a general rule I advise individuals consuming carbohydrate to stick as much as possible to low GI ones, such as green vegetables, tomatoes and pulses.
Another advantage of lower GI foods relates to satiety. Quite a few studies have found that calorie-for-calorie, lower GI foods sate the appetite more effectively than higher GI ones. Obviously, this has important implications for those seeking to moderate the amount that they eat without going hungry. I was interested to read of a recent study which assessed the impact of glycaemic index on satiety in a group of 8 sedentary women . On separate days the women were fed a high- or low-GI breakfast. Some hours later they were given a set lunch to eat. After this, the women were asked to rate how satisfied they were.
Overall, women found they felt fuller after lunch on the day that they had eaten the lower GI breakfast.
This finding raised the possibility that eating a low GI meal, compared to a higher GI one, can lead to greater satisfaction from a subsequent meal, and perhaps less food intake overall too.
This is a potentially important finding, but it was not the only focus of this research. The investigators were also concerned with the impact that the GI of food may have on the metabolism of fat in the body. The investigators point out that in previous research, the ingestion of lower GI carbs led to enhanced fat burning during exercise in physically trained men and women. The investigators were keen to see if the same held true for more sedentary individuals. Metabolism of fat was assessed while women were sedentary for 3 hours after breakfast, and then during a further hour during which they walked.
Overall, fat-burning was greater during both the sedentary spell and during exercise after the low-GI compared to the higher GI breakfast.
What this study has found, therefore, is that lower GI carbs, compared to higher GI ones, can lead to improved fat burning and satiety for several hours. These seem to me to be very good reasons for choosing low GI carbs, over higher GI ones, wherever possible.
1. Fat Oxidation during Exercise and Satiety during Recovery Are Increased following a Stevenson EJ, et al. Low-Glycemic Index Breakfast in Sedentary Women. J Nutr. 2009 Mar 25 [Epub ahead of print]