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

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

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

  1. Yolande 4 September 2009 at 11:00 am #

    I eat natural foods as far as possible. The main source of artificial sweeteners in my diet is in the form of diet cola drinks (Coke lite). I’ve been drinking it for so long that the “real thing” (original, non diet) just doesn’t taste well. I know that soda drinks simply isn’t healthy. But then neither are fruit juices. So what should one drink in a hot country like South Africa, where hot drinks like coffee and tea just isn’t a real option for most months of the year? (Besides plain water that is…)

  2. Chris 4 September 2009 at 11:27 am #

    These are nasty little additions to food. While I concede weakness in (my) passing generalist comments I feel the taste of these things are appalling.
    Have hypotheses been reported that certain of them interfere with registration of satiety in the brain?
    These rank as worse than sugar (sucrose) in my appreciation but I also have growing concerns over the role of sugar in 21st c. issues.
    Sucrose is digested to glucose and fructose. Fructose is distinguished by needing to be metabolised in and by the liver, is it? Though under-read, I’m increasingly concerned.

    Artificicial sweeteners proliferate in so many products. They may be marketed as being beneficial or adding value for the consumer but whose interests do they really serve?
    You can safely bet that they are economically viable for the manufacturers and that their inclusion may contribute to extended shelf life. Try selecting art. sweetener free lemonade from the shelves. They have slipped en-masse into commonplace products; baked beans, cider, fruit squashes….

    Excellent topic (as ever) John. Selectivity of published research is alarming in many ways. Most of those visiting here will be well informed. The people most at risk are busy folks without time to take an extended interest – the majority, and these are no better of that the lab-rats you mention. While unbiased state funded, commissioned, researched and published work is a comparative rarity upon what grounds should we lend our trust to regulators be that here, in Europe or over the pond?

  3. Florence 4 September 2009 at 11:42 am #

    Make your own fruit tea, keep it in the fridge and drink that. Put some real lemon in water and refrigerate. Get used to plain water.

  4. simona 4 September 2009 at 12:27 pm #

    This is a very interesting topic that deserves more attention from the public, especially those people (especially women) who try to lose weight by using low-fat or no fat dairy products sweetened with artificial sweeteners and diet drinks.
    I have read, I think, all your articles and columns, Dr. Briffa, since you first published in the Observer magazine and I think that your articles are very important; your arguments are always backed up by research and are very convincing. Your work should be able to reach a wider audience than the one given by a blog. Is there any hope of a column in a main newspaper?

  5. John Spottiswoode 4 September 2009 at 1:33 pm #

    I have thought for some time that the mechanism for artifical sweeteners leading to weight gain is likely to be around the fact that they fool the body into thinking that it has plenty of sugar in the bloodstream. Therefore the body seeks to put what it sees as excess into fat, which it does as much as it can. Then because this is not real energy/calories, the person consuming the sweetener tends to get hungry very quickly after this, leading to more consumption and more going to fat.

  6. Tar Samad 4 September 2009 at 1:56 pm #

    Good article!

    Yolande, I was in a similar position to you, drinking lots of diet drinks as my way of taking in fluid throughout the day. I can’t stand full sugar soft drinks because you can practically feel your teeth dissolving. It’s a similar issue with fruit juices. I eventually settled on carbonated water – I realised what I liked about soft drinks was the fizziness and the flavour the CO2 imparted to the water. It might take a day or two to get used to but it’s a much better thirst quencher as you’re just drinking water and CO2, not a whole load of flavourings, colourings and other miscellaneous chemicals as well. Plus, most non-brand carbonated water is a fraction of the cost of soft drinks.

    Best wishes


  7. Tim 4 September 2009 at 7:20 pm #

    Does anyone know of a safe, natural sweetner? I’ve heard of Stevia, for example, but never tried it.

  8. Skylark 4 September 2009 at 7:34 pm #

    @Yolande, Along with the suggestions above re alternatives to plain old water, I also drink unsweetened coconut water. It’s a great thirst quencher and comes in convenient tetra paks. Also makes a great base for a protein smoothie, along with the unsweetened protein powder and plain frozen berries.

  9. chris 6 September 2009 at 11:52 pm #

    In ‘The Low GL Diet Bible@, Patrick Holford advocates ‘xylotol’, a low GL sweetener that does occur naturally in varying degrees in fruit; plums are rich sources, apparently.
    As xylitol occurs naturally and by virtue of evolutionary precedent one might anticipate it to be safe. I haven’t looked for it on sale and therefore I have not specifically seen it on sale.
    Sooner than be reliant upon artificial sweeteners it makes good sense to make an effort re-educate ones palette and reduce the sweet-tooth.
    Sucrose (refined sugar) ought to be regarded with caution because of the fructose component. Does honey constitute a favourable alternative if used in moderation?
    Finally, remember a diet generally rich in soluble fibre will partly mitigate the glycaemic load (GL) of simple carbohydrates and sugars by ‘buffering’ the digestion to glucose and the passage of glucose from the gut into the blood. For eg, having included green leaves and/or, say nuts, in a meal will offset the GL impact of a sweet dessert to a degree by potentially and partially smoothing the resultant blood-sugar spike.
    Kathleen DesMaisons addresses the addictive nature of sugar (and perhaps hyperinsullinemia) in more than one title. I have scanned a couple of her offerings and I fell she has something to offer in the way of good sense though I had been sceptical over the way some of the arguments were supported.

  10. Chloe 7 September 2009 at 6:32 am #

    I am interested in anyone’s experience in becoming ‘hooked’ or addicted to artificial sweetener? i am surely not the only person… i consume ridiculous amounts of the stuff.. and go a bit demented if i try to cut back.. anyone?

  11. Dr John Briffa 8 September 2009 at 2:46 am #


    Are you (or anyone else) aware of any useful human research regarding the health effects/safety of xylitol. Part of the reason for asking is some years ago we had the promise of a low GI/GL, naturally occurring sweetener. It’s name? – fructose. And look where that got us…

  12. Chris 8 September 2009 at 6:46 pm #

    John, no, I hadn’t researched xylitol any more than having seen it advocated in the aforementioned book. I agree entirely about cause for caution. The entry in Wikipedia reads as though it could largely have been compiled by those of enthusiastic persuasion.
    The claim is that spoon for spoon there are 40% fewer calories than sugar but nothing is mentioned about relative sweetness. For all I know one might need to use 40% more of the stuff to satisfy ones palatte. There is a link in the wiki to the BMJ; it is not available to me.

    It would be interesting to understand how this sugar-alcohol is digested and metabolised. There is mention of a laxative effect – perhaps 40% passes out undigested?

    I have some additional paragraphs available in the link.

    residing in South Africa why not consider ‘rooibos’ (‘redbush tea’); a drink native to that country. Devoid of tannins it does not stew and is refreshing warm, tepid or cold. Devoid of caffeine it is a good way to reduce dependency to that, too. I prepared some yesterday and took it with me to work last night chilled and in a used squash bottle. It is fun to try adjuncts as diverse as your imagination allows. Top of my list are root ginger, mint leaves, lemon, lime etc. I confess I do sweeten but only to the degree of a pea sized blob of honey to a litre or more.
    I might try grinding dates, almonds or apricot kernels as alternative sweeteners.

  13. Lucy 9 September 2009 at 1:04 pm #

    Anyone looking for alternatives to diet pop could try home-made kombucha, water kefir, real ginger beer, or lacto-fermented sodas. A batch takes minutes to make, costs pennies, contains very little sugar, tastes great, and contains probiotic organisms, vitamins and minerals. Starter cultures and recipes can be found online, or in the case of lacto-fermented soda you can make the starter culture yourself.

    It’s also worth noting for those concerned about the effect of fizzy pop on teeth that the very high acidity of commercial fizzy drinks is even more disastrous for the teeth than their sugar content – and the acidity is just as high in the diet variety.

  14. Trinkwasser 11 September 2009 at 7:40 pm #

    I’m under no illusion that sweeteners are beneficial but I still use Splenda in my coffee, it’s about the only thing I need to be sweet and this one has less aftertaste than the alternatives *to me*, YMMV.

    Be a bit wary of sugar alcohols, responses may also vary. Some diabetics find some of them may cause a BG spike just like sugar while others are converted directly to loose bowels! It pays to test your own response to the different types.

  15. Chris 28 December 2009 at 9:04 pm #

    New Scientist in the their 19th December 2009 end of year issue give some coverage to the quest for the calorie free sweetener and the difficulties ensuing. Link here.

    It doesn’t detract me from my belief that refined sweetener, natural or otherwise, is likely to have undesirable consequence. Best to re-educate and wean oneself away from a sweet tooth.


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    […] Artificial Sweeteners – artificial hope? By getfatgetthin Dr John Briffa raised the issue of artificial sweeteners in his blog of 4th September 2009 headed: The myriad of reasons why artificial sweeteners may not deliver on their weight loss promise”… […]

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