The myriad of reasons why artificial sweetners may not deliver on their weight loss promise

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Artificial sweeteners enhance the palatability of foods but, unlike sugar, are virtually devoid of calories. The implicit promise here is consuming them, rather than sugar, is a better option for those seeking to control their weight. Now while the idea that artificial sweeteners offer advantages in weight control makes sense, you might be surprised to find that there is really no good evidence to support this notion. Not one single properly conducted study exists in the scientific literature that proves this supposed benefit. There are only two explanations for this: either the studies haven’t been done, or they have been done but haven’t been published.

I don’t know the truth here, but I suspect the latter. After all, you might imagine that the artificial sweetener industry would, among the voluminous research it has undertaken, at least have a bash at proving the effectiveness of its products. And we know that there is evidence which suggests the industry likes to publish research it likes, but perhaps be more reticent about having less favourable research see the light of day. For example, an on-line review of studies on the safety of the artificial sweetener aspartame [1] shows that while every single industry-funded study conclude aspartame is safe, 92 per cent of independently funded research identifies potential for this substance to have harmful effects.

Also, it’s worth bearing in mind that there is evidence that artificial sweeteners have effects that would not promote weight loss. They seem, for example, to have the capacity to mess-up the mechanisms we use to regulate food intake. One study, for instance, assessed the effect that artificial sweeteners have on the brain [2]. In this study, women were given a drink a solution containing either the artificial sweetener sucralose (brand name Splenda) or sucrose (table sugar). Brain monitoring showed that sugar activated the regions of the brain involved in registering pleasure more extensively than drinking sucralose.

This difference was found despite the fact that individuals were unable to distinguish between sucrose and sucralose on the basis of taste. In other words, while individuals are unable to consciously distinguish between sugar and sucralose, the brain appeared to know the difference. And it appears that an artificial sweetener may simply not give the level of pleasure and satisfaction that may be derived from sugar. This, in turn, could lead individuals to seek satisfaction from other foodstuffs.

In another study, just putting an artificial sweetener (saccharin) on the tongues of subjects caused insulin levels to rise [3]. This may induce low blood sugar and a form as false hunger that can lead to overeating as well as craving for carbohydrate-rich foods.

Other evidence shows that artificial sweeteners do indeed have the capacity to stimulate the appetite. For example, one study found that women given saccharin-sweetened lemonade were found to consume considerably more calories overall compared to those drinking regular (sugary) lemonade [4]. In another study, experimenters found that subjects who had eaten yoghurt sweetened with saccharin were inclined to eat more than those who had eaten yoghurt sweetened with sugar [5]. There is other evidence which suggests that aspartame too has the capacity to stimulate the appetite [6].

Then, on top of all this, I yesterday came across reports of another mechanism which may render artificial sweeteners quite useless as aids to weight loss. You can read the report here. The details are sketchy, but the claim here is that artificial sweeteners have the capacity to enhance the absorption of sugar from the gut ” something that is not good for a variety of reasons. The principle problem here is that it will, in theory, bump up insulin levels, and as all good students of biochemistry know, this hormone plays a pivotal role in the manufacture and accumulation of fat in the body. Also, it increases the risk of an episode of low blood sugar that can stimulate the appetite, including for sweet foods such as biscuits, cakes and soft drinks.

So, you see, there are lots of reasons why artificial sweeteners may not deliver on their weight loss promise. Come to think of it, there’s a few reasons why they may actually promote weight gain. Could this be why no properly conducted studies on the impact of these compounds on weight in human subjects have seen the light of day?

Again, I don’t know, but what I do know is that if no human research is available, then we have no option but to look to animal studies. In one study, rats were fed with either saccharin or sugar-sweetened yoghurt in conjunction with their normal diet [7]. The rats consuming saccharin ate more calories than their sugar-eating counterparts. Not only this, but they gained more weight, and more fat, too. The authors of this study concluded that ‘using artificial sweeteners in rats resulted in increased caloric intake, increased body weight, and increased adiposity’ and that, These results suggest that consumption of products containing artificial sweeteners may lead to increased body weight and obesity by interfering with fundamental homeostatic, physiological processes.

Now, the absence of human studies in the scientific literature means that we just can’t say for sure what effect artificial sweeteners have on our weight. But there is a growing body of evidence which suggests that the chances of weight loss through the use of these chemicals is very slim indeed.



2. Frank GK, et al. Sucrose activates human taste pathways differently from artificial sweetener. Neuroimage. 2008;39(4):1559-69

3. Just T, et al. Cephalic phase insulin release in healthy humans after taste stimulation? Appetite. 2008 Nov;51(3):622-7

4. Rogers PJ, et al. Separating the actions of sweetness and calories: effects of saccharin and carbohydrates on hunger and food intake in human subjects. Physiol Behav 1989;45:1093″1099

5. Lavin JH, et al. The Effect of Sucrose- and Aspartame-Sweetened Drinks on Energy Intake, Hunger and Food Choice of Female, Moderately Restrained Eaters International Journal of Obesity. 1997;21:37-42

6. Tordoff MG, et al. Oral stimulation with aspartame increases hunger. Physiol Behav 1990;47:555″559

7. Swithers, SE, et al. A role for sweet taste: Calorie predictive relations in energy regulation by rats. Behavioral Neuroscience. Vol 122(1), Feb 2008, 161-173

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