Which of the following has the lowest and the highest GI? Shown are yogurt, barley, avocado, parsnip, tomatoes, Snickers bar. See below for answer. (Louise McCoy/The Epoch Times)
Why? Because for most of us, hunger is not something we will willfully put up with in the long term. It is a major reason why individuals default from dietary change, and also a major reason why, generally speaking, diets don’t work.
At first glance, the idea of eating less without being hungrier does not make sense. But it does when one considers the fact that different foods satisfy the appetite to different extents.
One factor that appears to play a part here is the speed and extent to which a food releases sugar into the bloodstream (the food’s “glycemic index” or GI). There is plenty of evidence that shows that lower GI foods are, calorie for calorie, more satisfying than higher GI ones [1]. I wrote about this in this column last month. [theepochtimes.com/n2/content/view/18536/ ]
That column in June was about a study that found that a diet lower in carbohydrate and higher in fat was more satisfying than a higher-carb, lower-fat one. It was mentioned that lower-GI foods have a greater blood-sugar stabilizing effect than higher ones. This is good because they will help to prevent episodes of lower blood sugar (hypoglycemia) that can stimulate hunger and food cravings.
I also mentioned that the higher fat content of the more satisfying diet might have helped here too, in that it stimulates the hormone cholecystokinin, which promotes feelings of satisfaction and fullness.
I was interested to read recently about a study published this month in the European Journal of Clinical Nutrition that tested the biochemical impact of high and low GI diets [2]. The biochemical parameters checked were levels of glucose, insulin, cholecystokinin, and ghrelin (ghrelin is a hormone that stimulates appetite).
The lower-GI diet led to lower levels of sugar and insulin, perhaps not surprisingly. What would have been more useful is for sugar levels to be checked for any episodes of subnormal sugar levels. A study that took this approach found that the extent of low sugar levels tallied with hunger levels [3].
This study found no difference in ghrelin levels after the two diets. However, it did find that over a seven-hour period after eating, cholecystokinin levels were higher after the lower GI food.
To reiterate, this hormone helps promote feelings of satisfaction and fullness. Traditionally, it is thought to be secreted in response to fat. However, fat levels were the same in the two test diets. Here, we have a new mechanism that helps to explain the observation that lower-GI foods are more sating than higher ones.
References:
1. Roberts SB. High-glycemic index foods, hunger, and obesity: is there a connection? Nutrition Review 2000 58:163–169
2. Reynolds RC, et al. Effect of the glycemic index of carbohydrates on day-long (10 h) profiles of plasma glucose, insulin, cholecystokinin, and ghrelin. European Journal of Clinical Nutrition 2009;63:872–878
3. Arumugam V, et al. A high-glycemic meal pattern elicited increased subjective appetite sensations in overweight and obese women. Appetite 2008;50(2-3):215–22
Dr. John Briffa is a London-based physician and health writer with an interest in nutrition and natural medicine. His Web site is drbriffa.com
Answer: The yogurt, tomatoes, and avocado have the lowest—GI 15. Barley is 25. The parsnip is the highest at 97. The Snickers bar is 40.
