Artificial sweeteners found to boost weight gain in animals

Artificial sweeteners such as saccharin and aspartame have the ‘promise’ of being better than sugar for weight control because, although sweet, they contain virtually no calories. It’s a nice theory, though the reality is I cannot find one single properly conducted (randomised, controlled) study in humans exists in the scientific literature to support this. Now, there’s only two potential explanations for this. Either such studies have not been done, or one or more studies have been done but have not been published.

I actually don’t know which of these is the truth, but I am aware of previous research in animals which suggests that artificial sweeteners are not all they’re cracked up to be. In one study, rats were fed with either saccharin or sugar-sweetened yoghurt in conjunction with their normal diet [1]. Compared to those eating sugar-sweetened yoghurt, the rats eating saccharin-laced yoghurt consumed more calories and got fatter too. The authors of this study concluded that “…using artificial sweeteners in rats resulted in increased caloric intake, increased body weight, and increased adiposity [fatness]”, adding 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”.

Recently, I came across another animal study which gives me cause for concern. Here, rats were split into three groups, each of which was given unlimited amounts of standard rat food (chow) and water [2]. The groups were also given access to yoghurt sweetened with either saccharin, aspartame or sugar (sucrose).

In short, here’s what the results showed:

Rats eating the artificially sweetened yoghurt ate more chow than those eating the sugar-sweetened yoghurt. In the end, overall calorie intakes were the same. This suggests that when reduced-calorie foodstuffs are consumed, there can be a natural drive to seek those ‘missing’ calories elsewhere.

What was really interesting about this study, though, was that the rats consuming artificial sweetener gained weight at a rate faster than those eating the sugar. But the calorie intakes were essentially the same, meaning that change in weight could not be explained by differences in food intake. The authors cite another study from 2010 which essentially found the same thing [3].

It’s not clear what mechanisms are at work here. However, it was noted in a previous study [1] that rats experienced a boost in their temperature after eating sugar-sweetened food which was not present after eating saccharin-sweetened food. This suggests that consuming calories from sugar boosts the metabolism in a way that artificial sweeteners may not.

We do not know if these results apply to humans. However, one good thing about animals is that do give researchers the ability to strictly control and measure what they eat and the impact on weight. Here again we have evidence which shows that artificial sweeteners can stimulate weight gain. In the absence of good human evidence to the contrary, I’d say the evidence suggests that artificial sweeteners are unlikely to deliver on their weight loss promise.


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

2. De Mats Feijo F, et al. Saccharin and aspartame, compared with sucrose, induce greater weight gain in adult Wistar rats, at similar total caloric intake levels. Appetite 2013;60(1): 203–207

3. Polyák E, et al. Effects of artificial sweeteners on body weight, food and drink intake. Acta Physiologica Hungarica 2010;97(4):401–407

15 Responses to Artificial sweeteners found to boost weight gain in animals

  1. Dr. Bill Wilson 21 December 2012 at 8:00 pm #

    When dealing with the issue of “sweetness”, I think we have to ask ourselves why people prefer sweet foods. Most likely it’s because sweet foods like fruit are virtually never poisonous and throughout our evolutionary history fruit and berries were a good source of nutrition.

    In modern times this preference for sweetness has been elevated to a strong craving in individuals who tend to have some degree of insulin resistance and obesity. Although I like sweet food, I don’t crave sweets. Why is this so? I think it’s because I know how to maintain healthy brain function.

    Once sugar, HFCS and high glycemic carbohydrates entered the picture, this preference for sweets somehow got hijacked into strong cravings for sweet and starchy foods. We now think it’s because over time, these dietary elements can trigger a form of food-induced brain dysfunction called Carbohydrate Associated Reversible brain syndrome or CARB syndrome. People with CARB syndrome can develop up to 22 brain dysfunction symptoms and the first symptom is always craving sweet and starchy foods. Thus people end up eating more of the food that is frying their brain.

    If you are able to pull yourself away from sweet and starchy food, these strong cravings go away and brain function returns to normal. I agree with Dr. Briffa that taking the amino acid L-glutamine can be an effective way to suppress these pesky cravings, making it easier to follow a healthy diet.

    It seems that artificial sweeteners somehow magnify these cravings, increasing food intake, especially the wrong type of food.

  2. Robert van der Drift 21 December 2012 at 9:06 pm #

    2. De Mats Feijo F, et al. Saccharin and aspartame, compared with sucrose, induce greater weight gain in adult Wistar rats, at similar total caloric intake levels. Appetite 2013;60(1): 203–207

    2013 ??? We survived the end of the world and it’s still 2012…. 😉

  3. Michelle 21 December 2012 at 10:58 pm #

    Hi! I didn’t see sucralose mentioned here (Splenda). Would the results be the same or is sucralose a different animal all together? Season’s Greetings, btw.

  4. Nadia 22 December 2012 at 12:54 am #

    What about Stevia….?

  5. Jean 22 December 2012 at 1:07 am #

    What about Truvia? tried it on porridge for a month and have had strange pains like wind in my back and shoulders, think I’ll go back to sugar.

  6. emnesia 22 December 2012 at 2:19 pm #

    Does this apply to Stevia?

  7. mike pollard 22 December 2012 at 3:04 pm #

    I know it’s been said before, and might be a little simplistic. Sweetener hits the taste buds, brain expects sugar and pre-empts with an immediate insulin response. Blood sugar drops prompting more eating.

  8. Peggy Holloway 23 December 2012 at 2:43 am #

    I agree with Mike. I have strong symptoms when my blood sugar and insulin levels surge, and I have had those symptoms after consuming artificially sweetened food. The strangest experience was when I tried a “Zevia” soda when it was first introduced. Terrible symptoms (anxiety, shakiness, stomach growling, followed an hour or so later by “brain fog”) But, oddly, I don’t get symptoms from baked goods I make on occasion for holidays with sucralose and sometimes xylitol or Stevia in the Raw (erythritol gives me terrible digestive distress, and so does Truvia). I suspect that is because the butter, cream, and coconut or almond flour mitigates the effects of the sweetener and I use a very small amount of sweetener, so my “goodies” aren’t very sweet.

  9. John Walker 23 December 2012 at 4:41 pm #

    Hi Dr. Wilson,

    What might be a ‘healthy diet’ in your estimation? Just curious as to what you think.

  10. Chris 23 December 2012 at 10:09 pm #

    [.. ..] and throughout our evolutionary history fruit and berries were a good source of nutrition.

    Bill, I think you are right. I think aspects of distant of distant evolution could encourage a ‘sweet tooth’ as part of adaptive development, but the selection pressures that bear most upon behaviours exhibited today owe more to influences residing in the present day. I don’t so much disagree with you as I favour an alternate balance in emphasis.

    The articulation evident on the upper body of many a primate is said by some to be an adaptive response to spending time in trees and ‘reaching up’ to those branches above the boughs you’re resting on to get to choice fruits above. The emergence of bipedalism and bipedal locomotion requires something different that permits alterations to skeletal form of the hips and musculature that would otherwise be impeded by the prohibitively large gut of a frugivore.
    Those proto-humans as existed around 6mya lived in a largely arboreal habitat of tropical or sub-tropical diversity.
    The source(s) that has (ve) done most to colour my opinions suggests the early divergent proto-humans existed largely as folivores, pithivores, and frugivores. So it is conceived they ate a diverse diet largely comprised of plant matter garnished with grub or two. Mind you, they could not elect to eat to eat only plants in season, so although circumspect, the direction is they ripe and unripe fruits.
    It is hard to conceptually reconstruct the habitat they lived in and populate the model with likely edible plant species so we may never know precisely what they ate. Something we can be sure of, though, is that our modern perception of in season fruits would serve to misinform rather than inform upon the detail nature of the ‘ape-diet’ that prevailed in that phase of human evolutionary development.
    My sentiments owe a lot to conjecture, but the ‘ape- diet’ phase, coupled with what I believe to be the transitional phase that permitted the bipedal trajectory on route to becoming bipedal hunters suggest to me important signals controlling appetite are likely to be largely ‘fat-centric. And I agree wholeheartedly that introducing low calorie sweeteners could only result in ‘physiological confusion’, since adaptation is not at all pre-emptive.

  11. Chris 23 December 2012 at 10:34 pm #

    (doh!) .. the direction is they ate ripe and unripe fruits.

    .. And I meant to say I have a lot of respect for aspects of your CARB theory -which strikes me as mal-adaptive response to a circumstance adaptation didn’t anticipate.
    Eating carbohydrates, especially simple or refined ones, in the absence of the co-factors of either adequate fibre or suitable fat, would seem to be the departure from otherwise adaptive circumstance. I see no reason not to classify animal fats as suitable fats and every reason to imagine that solvent extracted ‘white oils’ commuted to shortenings and margarines are a development that the time-served process of adaptation could not pre-empt. 🙂

  12. Chloe 30 December 2012 at 9:26 pm #

    Surely they just make a sweet tooth worse?

    I remember at university studying nutrition my professor saying that thin people do not drink diet coke….

  13. Kelly Fitzsimmons 3 January 2013 at 8:12 pm #

    I don’t think there was any real doubt, atleast, not in my mind, that sodas, sweeteners, all the other fake sugars, are bad for us. It reminds me of the 80’s when smoking was still ‘unproven’ to cause lung cancers.
    If it isn’t natural, don’t eat it.

  14. Nadia 7 January 2013 at 11:21 am #

    The thing about pure Stevia… is that it IS natural and allegedly does not produce an insulin response. When I talk about Stevia, I am not talking about the artifical supermarket click click fizz stuff by the way. I’m talking about *pure* Stevia, from plants.

  15. Anna 8 January 2013 at 11:12 pm #

    There is a government clearinghouse for medical journal articles called “PubMed.” It contains complete abstracts of articles. Aspartame and MSG are said to have similar effects in the body. If you type “MSG obesity” into the search engine, you will find hundreds of articles referring to “MSG obese rats.” This practice is so common they don’t even explain it, but if you read a few abstracts, you’ll gleen that, when researchers want to do studies with obese rats, they produce them by giving MSG to baby rats, or to pregnant females who then produce obese offspring. Sure, it takes a lot of MSG, but how common is it for someone to down a bag of Doritos and wash it down with a liter of Diet Coke–and that’s only a fraction of their daily neurotoxin intake? When I first looked this up 10 years ago, there were no studies relating MSG (or aspartame) to human obesity, but now there are a few that link these chemicals to obesity, as well as hypertension and diabetes. Check it out; it’s definitely food for thought.

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