Weight control receives a lot of attention from doctors and other health professionals, scientists and the media, a reflection of the fact that there are burgeoning rates of obesity in industrialised countries around the world. While a number of dietary approaches have been advocated for weight loss, my preference is for diets that are relatively rich in protein and low in carbohydrate. And one major reason for this is the fact that, calorie for calorie, protein sates the appetite generally more effectively than fat or carbohydrate. And therefore individuals who up their protein intake often find themselves eating less overall because they’re less hungry.
However, how much satisfaction is derived from a meal from once it’s eaten and for the next few hours will not depend solely on its protein content (and how much is eaten of course). Fat and carbohydrate can also have distinct effects on feelings of fullness too. Fat, for instance, can stimulate the secretion of the hormone cholecystokinin from the small intestine that helps to keep the appetite sated for longer. Carbohydrate is important too, and what studies show is that those that release sugar relatively slowly into the bloodstream (lower glycaemic index carbs) and generally more satisfying than those that release sugar more quickly .
One reason for this is relates to the fact that faster sugar-releasing carbohydrates tend to cause the secretion of larger amounts of insulin, which can drive blood sugar levels down to lower-than-ideal levels. The end result can be a ravenous appetite, and sometimes craving for carbohydrates (often something sweet), about 2-4 hours after a meal. Now, even slower-releasing carbs can have this effect, if we eat enough of them.
I was interested to read about a study presented yesterday at the Endocrine Society’s annual meeting in Washington, DC, USA. The study assessed the relationship between two diets of different macronutrient composition on satisfaction. One diet provided 55, 27 and 18 per cent of calories from carbohydrate, fat and protein respectively. The other 43, 39 and 18. In other words, one diet offered less carb and more fat than the other. The diets were not designed to lead to weight loss, and were each tested for 1 month.
The results of this study have been reported here to show that those eating the lower-carb diet reported feeling fuller for longer after a meal.
One of the authors of this study, Dr Paula Chandler-Laney, is reported to have commented that this effect might have to do with blood sugar control. It’s possible, I suppose, that it might have something to do with the higher fat in the lower carb diet too. Dr Chandler-Laney also commented that a moderate reduction in carbohydrate intake may make individuals less susceptible to weight gain, because the effect such a diet may have on feelings of fullness and therefore, presumably, overall food intake. And she’s right.
But the other thing here is that less carb and less insulin in the body will likely mean less fat accumulation in the body, for biochemical reasons that were explored recently here.
1. Roberts SB. High-glycemic index foods, hunger, and obesity: is there a connection? Nutrition Review 2000 58:163-169