There are a number of ways of tackling excess weight, one of which is to eat less. What is important here is that food intake is cut without inducing much in the way of hunger. Why? Because for most of us, hunger is not something we will wilfully 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 more hungry does not make sense. But it does when one considers the fact that different foods satisfy the appetite to different extents. One factor which appears to play a part here is the speed and extent to which a food releases sugar into the bloodstream (the food’s ‘glycaemic index’). There is plenty of evidence which shows that lower GI foods are, calorie for calorie, more satisfying than higher GI ones [1]. I wrote about this only last month here.
This blog was about a study which found that a diet lower in carbohydrate and higher in fat was found to be more satisfying than a higher carb, lower-fat one. In this blog it was mentioned that lower GI foods have a more blood sugar stabilising effect than higher ones. This is good because they will help to prevent episodes of lower blood sugar (hypoglycaemia) 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 study published this month in the European Journal of Clinical Nutrition which tested the biochemical impact of high and low GI diets [2]. Biochemical parameters checked were levels of glucose, insulin, cholecystokinin and ghrelin (ghrelin is a hormone that stimulates appetite).
The lower GI diet led to a lower levels of sugar and insulin, perhaps not surprisingly. What would have been more useful, here, is for sugar levels to be checked for any episodes of subnormal sugar levels. A study which 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 7-hour period after eating, cholecystokinin levels were higher after the lower GI food. This hormone, remember, help 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, it seems, we have a new mechanism which 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. Briffa,
the amount of fat being in equal in the two diets means maybe it is the ratio carbs/fats rather than fat as such that causes cck secretion. Pardon my english, i am Dutch.
Thanks for your very interesting posts.I follow them closely.
Antje
Yes, that’s right. Or it might be down to something to do with the extent of sugar release (GI) of the carbs. Or both. Or perhaps some other factor(s).
The most important thing, though, is that lower GI foods are generally more sating than higher GI ones. Protein is generally sating too, by the way.
Fascinating! Give it another decade or two and we might have a better idea of how all this works. At the moment we seem to be discovering new factors (leptin, ghrelin, incretins, anandamide etc) faster than we’re working out what they do