Aspartame: Cause of or Solution to Obesity?

Image by Jake Spurlock

Last week fellow Plogster Steve Silberman forwarded me a link to this interesting article on the health effects of aspartame (the sweetener used in Diet Coke, among other things).  It discusses the evidence, or rather the lack of evidence linking aspartame with various types of cancer.  The article was well-outside of my area of expertise (I’m hoping that my PLoGs colleagues David and Melinda may share their 2 cents on the aspartame-cancer issue), but it did remind me of an issue that’s been coming up for some time in obesity research:

Is aspartame a cause or a cure for obesity?

Aspartame itself has no calories, so it couldn’t possibly result in increased body weight, right?  This is where things get interesting.  You see, some evidence suggests that aspartame may somehow increase hunger/energy intake, resulting in greater caloric intake and increased risk of obesity.  Here is what I had to say about the topic in a post back in January of 2009:

An article published last summer by Sharon Fowler in the journal Obesity suggests that individuals who consume diet soft drinks are at dramatically increased risk of overweight and obesity than those who do not consume diet soft drinks. For example, over an 8-year period, individuals who consumed just 3 diet soft drinks a week were 40% more likely to be overweight or obese than those who consumed none. The risk of overweight and obesity continued to increase dramatically with increased diet soft drink intake, and was independent of other factors like exercise, smoking, and socioeconomic status.

The Fowler study doesn’t prove that diet soft drinks cause obesity (people who drink more diet soft drinks may also have other behaviors that put them at increased risk for weight gain), but they are still pretty surprising. While diet soft drinks may themselves be free of calories, recent evidence suggests that they may increase caloric intake at future meals. For example, when rats are given access to unlimited amounts of food, those who are used to consuming calorie-free drinks eat dramatically more than those who are used to consuming drinks flavoured with sucrose. It may be that calorie-free drinks impair the body’s ability to anticipate the caloric content of a given meal, eventually resulting in increased caloric intake and weight gain. Others have suggested that calorie-free sweeteners like aspartame may also increase appetite at future meals.

Our friend Yoni Freedhoff of Weighty Matters (who works with patients with obesity on a daily basis) is unconvinced (emphasis mine).

Researchers in New Zealand studied folks who had successfully lost weight and their dietary consumption patterns. More specifically they looked at folks who had maintained a weight loss of greater than 10% of their weight for 11.5 years and they compared these folks’ dietary strategies to folks of similar weights who had never been overweight.

What unshocking yet valuable results did they find?

They found that folks who lost the weight had to work harder at their dietary strategies to help keep that weight off than folks who never had weight to lose. Their strategies included consuming fewer calories from fat (though the importance of this one’s debatable as the 90s were the low-fat decade and more recent data from the National Weight Control Registry suggest that low-calorie is of course more important than low-fat and can be accomplished many different ways), consuming more of sugar and fat modified foods (reduced fat, reduced sugar), consuming more water, less pop and three times more daily servings of artificially sweetened soft drinks.

So what gives?  Does aspartame make you gain weight, or is it a useful weight loss tool?  And more importantly, who is right – me or Yoni?  I honestly have no idea, although I’m guessing that the answer is somewhere in the middle.  A new review in the Yale Journal of Biology and Medicine looks at the evidence linking artificial sweeteners (aspartame, sucralose, etc) and body weight, and it’s not terribly conclusive one way or the other:

…consensus from interventional studies suggests that artificial sweeteners do not help reduce weight when used alone [2,25]. BMI did not decrease after 25 weeks of substituting diet beverages for sugar-sweetened beverages in 103 adolescents in a randomized controlled trial, except among the heaviest participants [26]. Adouble blind study subjected 55 overweight youth to 13 weeks of a 1,000 Kcal diet accompanied by daily capsules of aspartame or lactose placebo. Both groups lost weight, and the difference was not significant. Weight loss was attributed to caloric restriction [27]. Similar results were reported for a 12-week, 1,500 Kcal program using either regular or diet soda [28]. Interestingly, when sugar was covertly switched to aspartame in a metabolic ward, a 25 percent immediate reduction in energy intake was achieved [29]. Conversely, knowingly ingesting aspartame was associated with increased overall energy intake, suggesting overcompensation for the expected caloric reduction [30].

What possible mechanisms are involved in whatever is going on with these non-caloric sweeteners?  They cite a number of studies which suggest that real and artificial sweeteners have different effects on the brain:

Sweetness decoupled from caloric content offers partial, but not complete, activation of the food reward pathways. Activation of the hedonic component may contribute to increased appetite. Animals seek food to satisfy the inherent craving for sweetness, even in the absence of energy need. Lack of complete satisfaction, likely because of the failure to activate the postingestive component, further fuels the food seeking behavior. Reduction in reward response may contribute to obesity. Impaired activation of the mesolimbic pathways following milkshake ingestion was observed in obese adolescent girls [45].

The full text of the paper is available in Pubmed Central, so I’d strongly urge everyone to go check it out by clicking here.  Unfortunately there have yet to be any truly systematic reviews on the topic, so it’s going to be a while before we have a clear answer as to the role of artificial sweeteners in obesity and weight management (the above review doesn’t cite the paper that Yoni discussed – probably because it came out just before the review was written, but it makes me wonder what else a systematic review might find).

Others have also  discussed the issue of aspartame and obesity of late.  Stephen Novella of Science-Based Medicine covered the topic briefly in his recent post on all things aspartame, and is taking a cautiously optimistic approach to aspartame and body weight:

The question of aspartame and weight control is a complex one, and can be approached from many research angles. Here is a recent review of research [Travis’ Note: this is the Yale review I mentioned above]. At present the question is very much unsettled. It seems that there is no significant metabolic and no demonstrated neuronal effect from artificial sweeteners. However, people who knowingly consume diet drinks do tend to overcompensate by consuming greater calories overall. While studies of substituting aspartame for sugar in a blinded fashion show that calories are reduced, contributing to weight loss.

By my reading, the current summary of available research is that consuming calories in drinks contributes to weight gain and obesity, substituting calorie-free drinks (whether water or diet drinks containing artificial sweeteners) does help reduce caloric intake and aid in weight control, but there is a tendency to overcompensate by increasing other caloric intake. Therefore it seems reasonable to use artificial sweeteners to reduce caloric intake from drinks, but to be careful to control overall caloric intake (so no, putting aspartame in your coffee does not mean you can eat the cheesecake).

While I have not seen any papers demonstrating a neuronal effect of artificial sweeteners, some studies do seem to suggest that artificial sweeteners result in different patterns of brain activation than their full-calorie counterparts (examples here and here).  But whether those differences are meaningful in terms of weight maintenance, and in what direction, is up for debate (for example, this study suggests that aspartame results in beneficial changes in brain peptides related to satiety in rats), and I think that the approach Stephen is advocating is a pretty reasonable one given the current state of the evidence.

One thing that I haven’t seen any study address is how diet soft-drinks with and without caffeine differ in their physiological effects – caffeine inhibits the appetite and increases energy expenditure, so it’s possible that diet drinks with caffeine aren’t as obesogenic as diet sodas without caffeine.  In other words, this situation could get even more confusing than it already is…

So, what’s the take-home message?  I really don’t know, although people may find it interesting to note that we obesity researchers tend to consume an enormous quantity of diet soft drinks (I’d estimate that I personally I drink 2-3 diet cola’s a week, but I know many researchers who have at least one a day, often before noon).  Until the dust settles and the evidence is a bit more clear, I’ll stick with a slightly updated version of my conclusion from back in 2009:

So, while it is not yet completely clear what role diet soft drinks play in weight management, there are some good reasons to limit their intake to a moderate level, and to be careful that you don’t compensate for diet drinks by increasing your consumption of other high-calorie foods. Plain water is always a great choice, and if you find that too boring, consider adding a few slices of lemon or cucumber to add some fresh flavour. And as always, a little physical activity is always a good decision :)

I’m looking forward to some good discussion in the comments section!


ResearchBlogging.orgYang Q (2010). Gain weight by “going diet?” Artificial sweeteners and the neurobiology of sugar cravings: Neuroscience 2010. The Yale journal of biology and medicine, 83 (2), 101-8 PMID: 20589192

Related Posts Plugin for WordPress, Blogger...
This entry was posted in nutrition, Obesity Research and tagged , , , . Bookmark the permalink.

17 Responses to Aspartame: Cause of or Solution to Obesity?

  1. Cass says:

    Diet pop (and splenda) is part of my lifestyle weight maintenance program along with portion control and exercise. I’ve now kept 7 kg off for 10 years and after xmas usually knock off another 2 until summer. Really the only way I can see that artificial sweeteners would “make you fatter” unless you are overcompensating for the calories not consumed – just like you’ve said. Perhaps the trick is to not let people know they are eating calorie reduced food and gradually make smaller serving sizes the norm.

  2. Greg says:

    I’m a little surprised the Fowler article is mentioned, given the subsequent response published in Nature by Bursey. The controversy that the flawed Fowler paper originally stirred up ended soon after publication. Why resurrect it here?

  3. Donna Meness says:

    Keep in mind that a strong craving for sweets is a classic symptom of protein deficiency at the cellular level. A well-nourished system does not keep the “appestat button” (hypothalamus and pituitary) pushed, calling for more nutrients. Blood sugar becomes stable, and stamina and steadfast energy become new characteristics. Stabilization of the blood sugar takes effect usually within three weeks to three months after beginning a proper eating regimen.

    Aspartame is especially deadly for diabetics. All physicians know what wood alcohol will do to a diabetic. Physicians believe that they have patients with retinopathy, when in fact it is caused by Aspartame. Aspartame keeps the blood sugar level out of control, causing many patients to go into a coma. Unfortunately, many have died. Many people who switched from Saccharine to an Aspartame product have eventually gone into a coma. Their physicians could not get the blood sugar levels under control. Thus the patients suffered acute memory loss and eventually coma and death.

    There are 92 documented symptoms of Aspartame, from coma to death. The majority of them are all neurological, because Aspartame destroys the nervous system. There is absolutely no reason to take this product. The Congressional Record said, “It makes you crave carbohydrates and will make you FAT.” The formaldehyde stores in the fat cells, particularly in the hips and thighs.

    Aspartame poisoning is commonly misdiagnosed because aspartame symptoms mock textbook ‘disease’ symptoms, such as Grave’s Disease. According to the Conference of the American College of Physicians, “We are talking about a plague of neurological diseases caused by this deadly poison.” Aspartame changes the brain’s chemistry. It is the reason for severe seizures.

    This drug changes the dopamine level in the brain. The phenylalanine in Aspartame breaks down the seizure threshold and depletes serotonin, which causes manic depression, panic attacks, rage and violence. Whenever you get a seizuring person off Aspartame, the seizures stop.

    Aspartame changes the ratio of amino acids in the blood, blocking or lowering the levels of serotonin, tyrosine, dopamine, norepinephrine, and adrenaline.

    The Food and Sciences Department at Arizona State University has questioned the safety of aspartame after finding that ASPARTAME BREAKS DOWN INTO METHANOL (wood alcohol-CH3OH) at 86° F and it would react the same, chemically, at a temperature 12 points higher (body temperature). Dr. Richard Wurtman of Massachusetts Institute of Technology, in a letter to Lancet 846;1060, November 9, 1985, provides subjective reports on the correlation between high aspartame ingestion and altered neurological behavior, including headaches, hallucinations and, ultimately, grand mal seizures. In three instances, the symptoms disappeared upon the elimination of aspartame from the diet.

    One of the amusing but sad findings on aspartame is that it makes you fat. Millions of people take NutaSweet or Equal to avoid sugar and thus avoid gaining weight. Animal experiments revealed years ago that aspartame increases the appetite of the animals for sugar and carbohydrates.

    Dr Richard Wurtman, a neuroscientist at the Massachusetts Institute of Technology, confirmed this in humans. In fact, the National Institutes of Health published a report listing 16 reasons why you should not take aspartame.

    This drug was once listed by the Pentagon as a possible biochemical warfare weapon. But they must have decided it would be more profitable to poison our citizens with it than to wait for a war.

    Dr. Roberts concludes: “More than half the population now consumes enormous amounts of a chemical that I regard as an imminent public health hazard.” Twelve hundred food products now contain aspartame. It’s difficult to avoid it unless you stick to fresh food.

    Monsanto, the creator of Aspartame, knows how deadly it is. They fund the American Diabetes Association, American Dietetic Association, Congress, and the Conference of the American College of Physicians. The New York Times, on November 15, 1996, ran an article on how the American Dietetic Association takes money from the food industry to endorse their products. Therefore, they can not criticize any additives or tell about their link to Monsanto.

  4. Pingback: #NYCscitweetup and Quick Links | A Blog Around The Clock

  5. Donna Meness says:

    Their own FDA toxicologist, the late Dr. Adrian Gross told Congress that aspartame violated the Delaney Amendment because beyond a shadow of a doubt it triggers brain tumors. Dr. Gross concluded and “if the FDA violates its own law who is left to protect the public.” In time political influence got the Delaney Amendment which forbid putting something known to cause cancer in food, repealed but that’s the corrupt Congress for you again. Aspartame in original studies triggered brain, mammary, uterine, ovarian, thyroid, pancreatic and testicular tumors.

    The damage doesn’t stop there as aspartame breaks down into a witches brew of toxins including diketopiperazine, a brain tumor agent. In secret trade information volunteered in congressional hearings it was admitted in the last paragraph that they (Searle) had to consider almost complete conversion to DKP and if they told the FDA they wouldn’t get approved. Searle and their CEO at the time, Donald Rumsfeld, currently Secretary of Defennce for the US, was intent on getting aspartame approved knowing full well that consumers in the population would get brain tumors just like the rats did in original studies and they didn’t care. Money was their only interest.

    Searle did studies in South America sacrificing people in poor villages who developed brain tumors and seizures. These studies showed that aspartame hardens the synovial fluids and destroys the central nervous system and brain. They did not publish them – another crime. People died in the studies.

    Web site:



  6. Greg says:

    Comments such as the one above continue to perpetuate old Internet-based hoaxes that today are often compulsory study for those enroled in sociology programs.

    For readers interested in more factual information, Virani, Mendoza, Ferreira, and Marchena offered in part the following response to Dr. Roberts’ infamous letter to them:

    “As Dr. Roberts noted, aspartame is metabolized into phenylalanine, aspartic acid, and methanol. The above-mentioned metabolites from aspartame are found in much higher quantities in foods and beverages of daily use. For example, a glass of non-fat milk provides about 6 times more phenylalanine and 13 times more aspartic acid, and a glass of tomato juice provides about 6 times more methanol than does an equivalent volume of beverage sweetened 100% with aspartame.”

    The information provided in the quote above can be independently confirmed from a number of sources, such as that published by Butchko et al. for example. I would also add that over the last 30 years, no other food additive has been subjected to such intense continuous scientific scrutiny, with literally 100s of independent clinical trials and studies undertaken in dozens of countries.

    If aspartame were truely a deadly poison that caused a plague of neurological diseases, would there not be more evidence available than the two annecdotal accounts from two medical doctors written during the late 1980s?

  7. Austin says:

    About 4 years ago, I finally lost the extra 40 lbs I’d put on in a decade of stressful desk work. While I cut out all sodas for a month at the start – mostly as a jumpstart -, I later resumed but drink almost exclusively diet sodas (Pepsi Max is my current choice) with a limit of one can a day maximum; out at the bars on Saturday Night, I might have the equivalent of two or three cans, but since I don’t drink it’s a compensation. So, diet soda has been a boon to me for dieting – and I’ve kept the weight off (other than muscle I’ve put on, which doesn’t count) ever since.

    That being said – I don’t have a sweet tooth. I don’t like most candy, don’t really eat desserts, and rarely indulge in pastries. I even prefer sugar-free popcicles when I have the craving, which is rare; they also have aspartame, but I honestly don’t think they’re very sweet (but that’s good; the sugared ones are too sweet). To me, sodas *are* my “sweet habit”, so switching to a diet soda doesn’t mean I consume more sugars in compensation.

  8. Carol says:

    I’m another one maintaining a 50 lb loss. (one year this month).

    I have a caffeine-free diet rootbeer (sweetened with splenda) with my lunch almost daily. Some days (mostly in the summer), I’ll have a 2nd diet rootbeer around 3pm. I write them down in my daily food journal along with all the other food / beverages consumed.

    Yes, I could give them up. I don’t want to however. They taste like a treat to me. And they fill me up. All anecdotal, I know, but it sure works for me.

  9. Kim Jensen says:

    Very well put Donna; As a distributor of natural supplements I have been schooled many times over on this Fraze. A well-nourished system does not keep the appestat button pushed, calling for more nutrients. Last year, at least 400,000 Americans managed to kill themselves based almost solely on what they ate. I would like to add or drank!. Aspartame no matter how it is ingested in time will kill you. So for the sugar junkies looking for the most effective,
    probably most enjoyable way to do yourself in.
    Have a diet cola as well as a doughnut. And make it cream-filled!

  10. I’ve downloaded the paper you refer to and am hoping it may contain part of the answer to a question that’s been puzzling me. I have an interesting family history that might be apropos here.

    Many years ago (decades, really) my Grandmother was hospitalized after consuming now-banned cyclamates. She had a serious reaction and passed out.

    My Mom was taken emergency rooms twice, unconscious and once close to shock, after consuming saccharine. She also experienced double vision both times. (The second was a bit funny–she thought nothing of seeing two doctors bending over her when she regained consciousness in the hospital, but realized there was a problem when she saw two husbands!)

    Naturally Mom kept me away from artificial sweeteners when I was young; but I was away for a weekend with a group of teens and women who’d only ordered diet sodas delivered to our cabin. Oh, how bad could it be, wondered my 17-year-old self? Half a can of diet root beer later, I knew–three days of unremitting nausea. Even a photograph of food made my stomach turn over. I avoided a hospital because I never passed out. I did lose eight pounds in three days, but I wouldn’t recommend it.

    A later accidental dose of aspartame (chewable allergy medication) made me less ill, but two little tablets left me with some tummy trouble–not serious, but too unpleasant to describe in detail here.

    What’s odd, you’ll notice, is that we all got ill on different things. Several doctors have told us that such a reaction cannot be hereditary. But there it is…

    Alas for me, there’s type 2 diabetes in my Dad’s family. (He has no trouble with diet soft drinks or artificial sweeteners.) So I’m in a double bind. In my late 40s, overweight and contemplating my gene pool, I realized I needed to lose weight–about 40 pounds, it turned out, to get my BMI down to 25-ish. Somehow I did it without a single diet soda! (People asked about that, as though it’s impossible. I’ve noticed that some folks seem to think diet sodas have “negative” calories that counteract the others they consume.) Actually, once I made the decision the weight came off pretty easily, one or two pounds a week except for a frustrating plateau at -29 lbs, through exercise and cutting out “junk” foods except for a once-a-week treat to keep me from going crazy. That treat sometimes included a can of sugar/corn sweetened soda–not the healthiest stuff around, certainly, but one can a week seems entirely do-able when the rest of my diet is sensible.

    So I’m left wondering: how is it that a 40-something woman can lose 20% of her body weight (in a little over a year) without a single drop of diet soda, while the “epidemic” of obesity seems to have only gotten worse since diet sodas became popular?

    • Travis Saunders, MSc, CEP says:

      I think you might be taking the title of my post a bit too literally – I don’t think there is any evidence that non-caloric sweeteners are the driving force behind the obesity epidemic, although there is evidence to suggest that they *may* be one of many risk factors for obesity (along with inactivity, short-sleep duration, and of course most importantly, high caloric intake). It doesn’t surprise me that someone could lose weight without using diet soda, just as it wouldn’t surprise me to hear that someone had lost weight without doing any exercise (e.g. through diet alone) or that someone had lost weight without any changes in diet (e.g. through exercise alone). Weight loss achieved by targeting one risk factor (or group of risk factors) does not necessarily prove that other risk factors are unimportant.

  11. Perry says:

    My own anecdotal evidence has convinced me that substituting regular sodas for diet sodas leads to weight loss. This might not apply for the general population but it seems to apply to me.

    And since they satisfy me equally (taste wise) there really isn’t any reason to consume regular sodas.

    It’s not surprising to me that someone who sells natural supplements is propagating non-scientific nonsense about the dangers of aspartame. To the people who say it is unsafe please answer this simple question…

    What evidence would you need to see that would prove to you it is safe?

  12. brtkrbzhnv says:

    I don’t see how the Fowler stuff was in any way surprising – of course the overweight are more inclined to consume weight-loss products such as diet soda. It’s like that study that showed fat kids drink less full-fat milk.

    The review mentioned by Stephen Novella mentioned this three-year intervention study, which showed a weight regain of ~100% more during maintenance and follow-up (after an identical weight loss) in the group instructed not to use aspartame than in the group instructed to use aspartame. This seems to me, as a layman, to be the kind of study most relevant to clinical practice. Another interesting study is this freely available one, where the blood-glucose response to aspartame was found to be highly variable, with increases in some individuals and declines in others, which apparently influenced subsequent food intake.

    Anecdotally, I personally have been using aspartame-sweetened beverages as a means to relieve hunger when I’ve experienced it at times I’m not supposed to eat, though I’m not entirely convinced of its efficacy (I’ve only been doing it for a couple of months, and not all that frequently, and it might be placebo or the water or the other flavors or regression to the norm), and I haven’t been able to find any studies on the short-term effects of low-energy sweeteners on people who are already experiencing hunger.

    One should also keep in mind that weight gain is not the only danger of excessive sucrose/HFCS consumption, so even if people do compensate in terms of energy consumption, they might still be better off when it comes to e.g. diabetes.

  13. Lisa says:

    Well, after a week off of diet coke and with a huge reduction in the pink packet stuff, I can say without a doubt that I no longer feel hungry all the time or have this strange gnawing in my stomach that I used to have every day that I thought was hunger… or something. I am also obese and have terrible trouble with cravings. This last week, I have easily avoided most temptation and have felt full (and lost weight).

    I have been an artificial sweetener person since the late 80s… drinking multiple diet cokes and/or other saccharin sweetened beverages every day. I have no doubt that this has messed up my system with gastric signaling (or something). I’m pretty angry that I didn’t know this and that I’ve struggled so much with cravings that I didn’t have to have.

    So, now I plan to get off of the pink stuff and the diet coke totally in the next week or so. I’m down to no diet coke and less than a pack of pink a day. I KNOW this is one of the missing links for many fat people… or at least some.

  14. Nicolas says:

    I have been drinking diet soda for the last 10 days and I have dropped 4 kilos. I don’t feel that hunger problem others seem to feel. Its all about control. Also adding to the 10 days was a diet of pure cooked potatoes and veggies. I am never in the mood for fattening foods since I am always too full because of the soda and potatoes.