Is Pepsi Max Bad For Your Weight?

The Pepsi Max Test

Can artificial sweeteners from diet sodas affect your weight? My six hour experiment the other day implies that the answer might be yes.

The results can be seen above. I drank the Pepsi Max (17 oz.) after about an hour. The black line is the blood sugar and the purple line is the ketones.


Earlier: Planning / Report 1

When the experiment started I was in pronounced ketosis since several weeks (due to a strict LCHF diet). I was fasting six hours before the experiment started.

The first four blood samples were taken before I started drinking Pepsi Max. Blood sugar and ketones were both a bit above 4 mmol/L (which equals a blood sugar of 72 mg/dl). The small variation in the first tests is probably due to the meter not being more exact (normal for home meters).

During the dark mark I drank the Pepsi (50 cl / 17 oz.), it took 10-15 minutes.

Blood glucose results

As you can see nothing special happened to my blood sugar during the experiment. It stayed at around 4,5 mmol/L (80 mg/dl) and the tiny variation is probably within the margin of error of the meter.

Ketone results

If nothing happened to my blood sugar the effect on my ketone levels were more dramatic. As I noted when planning the experiment one of my suspicions were that the artificial sweeteners might trigger a release of insulin. That would lower ketone levels, as ketones are very sensitive to insulin.

Fifteen minutes after drinking the Pepsi my ketone level appeared to drop, from around 4 to 3,4 mmol/L. Then it continued down during two and a half hours until it had dropped by almost 50 percent.

After that the ketone level started rising again. But when I stopped the experiment, almost five hours after drinking the soda, it was still not back where it had started.

What does this mean?

Pepsi Max and other products with artificial sweeteners are thought not to affect peoples weight, as they contain no calories. That’s an oversimplification that ignores any hormonal effects and resulting hunger. If the sweeteners slow your fat burning and increase your hunger they will of course affect your weight – calories or not.

What is clear from the experiment is that something happened. The ketone level dropped precipitously. My interpretation is that this potentially could result in a decreased fat burning, making it harder to lose weight. Perhaps this is due to insulin release, perhaps not.

I wonder: What if your fat burning is impaired for more than five hours, every time you ingest artificial sweeteners?

One objection: Was the culprit the artificial sweeteners or the caffeine in the soda? This experiment can’t tell, but I would gladly bet money on the sweeteners. Perhaps I’ll do a similar experiment later, drinking black coffee instead.

What do you think about the results?

Earlier experiments

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  1. Peggy, your instincts are accurate. The jittery feeling you described is the effect upon cells that have become "insulin resistant"... these cells are finally letting you know they have "reached the END of trying to process sugar overloading, by saying "I've had enough and cannot cope!" by continued bombardment of "sugar spikes". The body works at it's best in a CONSTANT LOW SUGAR state, when it can easily and readily "switch" from one "fuel tank" to another...e.g. from burning carbs (preferably from whole foods such as vegetables) to burning stored or recently ingested good high quality fats (undamaged and unprocessed whole fats, if these are heated > this must be below their smoking point). Cells that have become damaged "insulin resistant" cells can no longer properly process nutrition INTO the cell and toxins OUT through the cell membrane. This increases your susceptibility to store fat as body fat. This decreases the ability of your ingested nutruition to actually get into the cell > where it is needed. This is how "high sugar spikes" make cells dysfunctional, cause the pancreas to eventually "give up" producing insulin, make your body store fat, give you the rollercoaster of high/low blood sugar.
  2. murray
    Blood sugar could remain stable in the presence of insulin because of glucagon, especially as Dr. Eenfeldt appears to be keto-adapted.

    I also ask why not test insulin simultaneously.

    A possibility to consider is that the taste of sweetness in the mouth activates release of insulin in anticipation of incoming sugar. It's not good to fool Mother Nature. Try swishing Pepsi Max in the mouth several times in the ten minutes without drinking it and observe the result.

    As for suggestions about multiple testings to get statistically significant data, how many ketone test strips can Dr. Eenfeldt afford? They are expensive in Canada. I assume he is looking for game-changing data to guide inquiry and not scientific proof beyond reasonable doubt.

  3. Ken
    Am I the only one wondering why Frances Wellington doesn't know how to spell her own name?
    Reply: #93
  4. wickedchicken
    Pepsi max does something to me ((that is, makes me verrrry happy from a sweet high)). I can feel a chemical surge when I drink it, no joke. So, though I love it, I avoid it.... I switched to water and plain carbonated water, and tea, decaf coffee only. Thought there would be some miracles as I was seriously drinking a lot of Pepsi max before. But nope, not a peep of a fat or weight change despite my diet and exercise attempts too. And then after 2 months of full motivation... I was breaking ketosis... Craving sweets... Avoiding Pepsi max so eating pick n mix instead! Oh my. Not good. Back to base and I'm keeping off ALL this time!

    Well that's my Pepsi max 2 cents :) interesting result and would be verrrry interesting to see the same trial in an obese man. I would also like to see how many vegetables one could eat and keep ketosis.

  5. Digby
    I understood that artificial sweeteners affected insulin and only ever consumed them with food, but now I wonder if they might still be bad regardless.
  6. I read an article that stated thinking if something sweet can lower your keytones... Maybe it is mind over matter...?

    This is a terrific idea! Track ketones over a period of a few hours to establish baseline, then at t=0 begin a focused imagined eating exercise. Imagine eating and drinking a variety of sweet foods.

    Another interesting possibility might be to conduct an experiment where the subject smells (rather than eats) sweet foods, while blood ketones and glucose are measured.

  7. laura
    Ok jsut an idea. I ahve not had the time to read all teh posts above so apologies if someone has suggested this already....but how about testing water carbonated and/or still with the same sweetener added as the soda you tested in teh same relative amount?
    or repeating the test with different sweeteners to compare effects on ketons (on different days of course)

    About the thought of food affecting ketones...I thought it was well known that anticipating food consumption stimulates insulin secretion and should affect ketons but also bllod sugar.
    Still cannot quite work our why the doc's blood sugar did not change!

  8. Justin B
    Oly, In response to #3, the 1g carb for packets of sweeteners is due to the maltodextrin that is used as filler. They actually do contain 0.9g carbs due to this. Soda products don't contain that filler, since they can just use the pure stuff.
  9. Justin B
    "Epidemiologists" and "associated" are key words that make a study near-useless. All that study can be used for is a basis to find further funding to conduct an actual study. They have formed a hypothesis, nothing more. If we're going to be critical of the bad science that mainstream nutrition purveys, we have to apply the same criticism to things that align with our own beliefs. They did not control anything. The outcome of this study can just as easily be "Diet soda drinkers think that they can make up for bad eating habits by drinking diet soda, but they can't", or "diet soda drinkers follow a low-fat regimen, but gain weight instead of losing".

    My parents' fridge is loaded with sugary, floury things, but the drink that lines the door is diet soda.

  10. Diane
    Even if Pepsi Max doesn't mess with your insulin or blood sugar or even your ketones, it isn't real food, so I am not going to consume it.
  11. Jay Wortman MD
    After I gave a lecture to the medical class, a student came up to tell me that he had lost 20 lbs
    and that all he had done was switch from regular Coke to diet Coke.

    My $0.02 worth, caffeine is a confounder so you should try this with caffeine-free diet cola. Also, for those who have insulin resistance, a small surge in insulin, while it may not be enough to drop blood sugar, may be enough to limit fat oxidation. For those who are strictly adhering to a low-carb diet and not losing weight, it is worth the effort to try eliminating artificial sweeteners. The importance of this likely depends on the degree of insulin resistance that has developed.

  12. Agustin
    Seriously Katie, do it, it WILL NOT happen, that's a huge exageration.
  13. Steve Bergman
    I agree. And the fact that both the experimenter & the subject are on record as being anti-artificial sweetener adds another issue. Of course, the fluctuation could also have been random, or caused by some other factor, unrelated to the soda.

    And then there is the issue of whether a minor, temporary fluctuation in ketone level will "affect your weight".

    All in all, this is worse than even the "science" presented on the nightly news on TV.

  14. Hugh
    FACT - Aspartame is a poison 1000x sweeter than sugar and manufactured from the faeces of e-coli bacteria. It also contains formaldahyde!
    FACT - It was promoted by Donald Rumsfeld
    Do your homework people
  15. Paul
    It was recently discovered that our small intestine has taste buds to sense sweetness:

    From the article:

    "Carbohydrate ingested from meals & beverages breaks down into glucose, which stimulates the sweet-sensing proteins in these gut taste cells. Activating the sweet--sensing proteins of the gut taste cells promotes secretion of glucagon-like peptide-1 (GLP-1), an intestinal hormone that plays a key role in promoting insulin secretion and regulating appetite."

    So, even with no carbs at all, the taste of an artificial sweetener may fool your body into secreting insulin because it's expecting a blood sugar spike.

    Reply: #67
  16. 1 comment removed
  17. Steve Bergman
    I should repeat my earlier note that this totally unscientific, ad hoc, one-off anecdote is meaningless for a plethora of reasons.

    However, for the sake of hypothetical argument... if insulin increased, why would blood ketones be affected but not blood glucose?

  18. Fran
    I am curious about a similar test with black coffee!
  19. murray
    I get the points about scientific rigour, but that is not how discoveries are made. There would be no LCHF movement if not for ad hoc experimenting by clinicians in practice and bio-hackers who share insights, whether in meetings or through the Internet. Weston Price did an interesting survey of nutrition and health in many cultures in the 1930s that had yet to adopt Western diet. Several of the cultures through adaptive experience implicitly discovered that vitamin K2 (which Price called Activator X, as it was as yet unknown to "science") was important to several aspects of health and that ruminants grazing on fast-growing grass were especially suitable for this. Call this knowledge acquisition primitive crowd-sourcing, perhaps.

    Of course, the methods of scientific rigour identified vitamin K2 in 2005 or so and subsequent research has confirmed the ways and means by which it affects calcium delivery and other aspects of health. But who wants to wait 75 years for iron-clad scientific proof.

  20. Steve Bergman
    Lack of scientific rigor, bad science reporting, and irresponsible blogging are also responsible for much of the rampant misinformation that so many (most?) people accept uncritically. You can't defend the above drivers simply by pointing to a rare exception.

    Reporting ad hoc results is fine. But "Is Pepsi Max Bad For Your Weight? ... My six hour experiment the other day implies that the answer might be yes." conveys a level of relative confidence that one might expect in a peer-reviewed paper reporting the results of a small study with random assignment of subjects, where the experimenter was not also the sole subject.

  21. murray
    Yes, Steve, I agree one has to be critically astute to make good use of data. As Nietzsche observed, there is text and there is interpretation. Most science reporting is interpretation and even most experimental design is interpretation-biased. But they do generate data and I would rather have access to the data points and filter through the interpretation.

    For example, I am reading Thomas Seyfried's new book, Cancer as a Metabolic Disease, and a pilot study on using ketogenic diet for terminal cancer patients. They all had a low-carb diet, but only the ones that achieved significant ketosis had their cancer stabilize or go into remission. Dr. Eenfeldt's blog now twigs me to ask, did they control for consumption of Pepsi Max?

    Replies: #72, #74
  22. Steve Bergman
    I wonder if they controlled for consumption of heavy cream. After all, heavy cream is sweet and can thus knock people right out of ketosis. (It's been observed by clinicians.) But only some people, mind you. Not everyone. So if you and all your friends use lots of heavy cream, and it doesn't affect your ketosis, that's just because you don't happen to be in that 25% of people whom are thought to be sensitive. I know a guy who was doing great on Atkins until he had some heavy cream. It took him 3 weeks to start losing weight again. YMMV.

    Once lack of scientific rigor is accepted, it's trivial to come up with all manner of claims which are resistant to refutation. The above strategy is the one most often used against aspartame by LCHF advocates who dislike it (inclusive of the 25% figure). I just substituted "heavy cream".

    I hold the tenets underpinning the power of science to be very dear, indeed. And I tend to be a stickler for observing the rules that keep scientists honest. Not just in this field. But wherever science is relevant.

  23. Murray Braithwaite
    I agree. I note that the leap from Pepsi Max caused the ketone level to drop to aspartame caused the ketone level to drop is interpretation, likely driven by confirmation bias. I can be reasonably confident (but not certain) that Dr. Eenfeldt did not do anything else relevant during the test period and the effect would be reproducible. It does not help at all to identify what aspect of the Pepsi Max consumption was relevant.

    This is how allergies and food sensitivities are identified in individuals. My allergies are not identified by running a double blind randomized intervention study on a population. I avoid the food for a few weeks and if the symptoms disappear I reintroduce the food. If the symptoms recur, I may have the culprit. After a few of these I gain confidence. My wife identified that she gets headaches and migraines from wheat this way. For years her headaches were getting worse. At least 5 headaches per week and a few migraines per month. She saw the leading headache/migraine physician in the country and got prescriptions that blunted the pain. Last winter she tried removing wheat from her diet and the headaches stopped abruptly. Within a couple of days she did not have a headache. She had not gone a week without a headache in the 18 years since I met her. No headache for weeks. Then she ate some cookies and had a migraine the next day. Headaches happened a few times when she unwittingly had flour in a sauce or dessert. So she is more careful now and never gets headaches. This may not be science, but she does not get headaches anymore.

    Reply: #79
  24. Raymund Edwards
    Murray. he does mention Caffeine and Coffee in that book (Thomas Seyfried )

    "I have recorded the blood glucose and ketone levels in several of my students who have voluntarily fasted for up to 6 days. The students were all healthy young adults (males and females) between 21 and 28 years of age. The students consumed only water or decaffeinated green tea during the fast. All students, both males and females, were able to bring their blood glucose and ketone levels into the therapeutic ranges within 3 days (Chapter 18). Most cancer patients should have a similar experience as long as they are not taking any interfering medications.

    Glucose withdrawal symptoms were experienced by most of the students over the first couple of days, but these symptoms were transient and gradually subsided after 2 days. It is interesting that glucose withdrawal symptoms (anxiety, headache, nausea, etc.) are also seen in many persons following withdrawal from other addictive substances such as alcohol, tobacco, and drugs. Some of the students felt energetic after 5 days of fasting. They all learned that fasting is therapeutic and not harmful.

    One of my graduate students, Julian Arthur, lowered his blood glucose to 39 mg/ dl by the third day of the fast. I asked Julian how he felt walking around with such low blood glucose levels. He said, “I feel fine, no problems.” Julian's blood ketones were also at 1.1 mmol, which would compensate for low glucose and prevent adverse effects of hypoglycemia. Hypoglycemia is a concern only for those individuals who lower glucose levels without also elevating their blood ketone levels. The gradual transition from glucose to ketone metabolism protects tissues from the effects of hypoglycemia. George Cahill and colleagues have documented these observations [52, 54, 55].

    Another student, Ivan Urits, was unable to lower his glucose to the metabolic range despite 6 days of fasting and elevated ketone levels (2– 3 mmol). His glucose was reduced only to 68 mg/ dl during the fast. It turned out that Ivan was drinking caffeinated black coffee, rather than drinking only water during the fast. Caffeine can prevent glucose levels from entering the therapeutic zone necessary to target the energy metabolism of tumor cells. Herbert Shelton argues against coffee consumption during fasting [51]. It would be better to consume calorie-free decaffeinated beverages than caffeinated beverages.

    I suggest that persons avoid caffeinated beverages if they plan to use the restricted ketogenic diet (KD-R) as an approach to prevent cancer. It will be up to each person to know what they can or cannot do to maintain their blood glucose within the therapeutic ranges. "

  25. "My six hour experiment the other day implies that the answer..." I don't think we get answers from one six hour experiment when they have no control. The first two comments give many explanations (assuming that a repeat of the experiment gives the same result which is unlikely; I always tell students that if you do 2 experiments you're going to have to do 3).

    First control would be to repeat the experiment with same volume of water at the same temperature.

    On the other hand, if the experiment could be interpreted in any way to indicate that saturated fat or fructose were bad, then it would be a wrap and you could submit to AJCN or directly to ABCNews.

  26. Murray Braithwaite
    Thanks, Raymond. You are further along than me. I got the book last week and have managed to get to just page 253, which, so far, is an extended review paper. A reader review I read on Amazon said the book reads like a mystery novel so I did not want to skip ahead. (The reviewer was a bit generous in this regard.) I hope you didn't have to type in that entire passage.
  27. PhilT
    "why would blood ketones be affected but not blood glucose?" - glucagon. If you eat steak there is a large insulin response, but you don't collapse in a hypoglycaemic coma because there is also a glucagon response telling the liver to push out glucose and maintain the blood sugar level.
    Reply: #78
  28. Steve Bergman
    1. The fat & protein in steak causes a large insulin response?

    2. Glucagon stimulates the release of glycogen stores. Where would the glycogen come from in a person who is already in ketosis?

    3. Where is the evidence that a transient decrease of 26.6% AUC in serum ketones over a 4.5 hour period affects weight loss? Where is the evidence that it is "bad for your weight", as the blog post topic suggests?

    And although I've already covered this, I should briefly reiterate that the design of the "experiment" does not allow us to conclude that the Pepsi Max consumption caused the changes observed. And certainly not any individual component. The blog post targets the artificial sweetener for no apparent reason other than personal bias. Others have have observed that caffeine can have this effect, which has been shown to be modestly *helpful* in weight loss for people on LCHF diets by stimulating uptake and use of ketones by cells.

    Is Pepsi Max Good For Your Weight? The results of this 6 hour experiment imply that the answer might be yes.

    Reply: #80
  29. Steve Bergman
    But your wife was changing an input, observing an output, and making an inference between the two based upon that.

    This experimenter was changing an input, observing two outputs (serum glucose & ketone levels), only 1 of which was affected (transient 26.6% decrease in ketone AUC over 4.5hrs, while glucose remained constant) and inferred that (specifically) the artificial sweetener in the input was "bad for your weight", leaping several large crevasses to reach that conclusion.

    I ask a few more questions in my response to PhilT. But this kind of "reasoning" makes Cold War Propaganda "logic" seem top drawer by comparison. It has very little in common with your wife's sensible ad hoc experiment and tentative conclusion.

  30. PhilT
    1. - yes, Table 4, beef steak creates insulin AUC response greater than some well known carbohydrates.

    2. covers the actions of glucagon on the liver, not only to release glycogen (which may not be in abundance) but also gluconeogenesis. This reference also covers the protein effect kicking up both insulin and glucagon to maintain blood sugar homeostasis

  31. Thank you, Dr. Eenfeldt, for provoking such a lively and intelligent conversation about artificial sweeteners and metabolism. Clearly there are many people here who have been inspired to think critically about all of the possibilities that this mini-experiment may imply, myself included. As so many "official" nutrition studies are critically flawed, or may not ask the questions that we the people most want and need answered, it is important for each of us to do our own individual dietary experiments to see what works best for us. Your test challenged the notion that these sweeteners are metabolically inert--is it a 100% conclusive study? Of course not. However, it has peaked my curiosity and has made me want to purchase a ketone meter of my own so that I can explore further how these and other substances affect my metabolism! Thank you~
  32. Steve Bergman
    Of course, rather than living with a "suspicion that artificial sweeteners might trigger a release of insulin" or trying to settle the matter with a poorly designed ad hoc trial with consumer grade equipment, one could just go to the literature to see if anyone has done the experiment properly. And of course, it's been done many times. With overweight people, normal weight people, diabetics, non-diabetics... you name it. Here's an example:

    Aspartame has the same effects upon serum insulin & glucagon levels as does a glass of water.

    Tempest, meet teapot.

  33. Michael
    Nice experiment by the way. There's a lot of little experiments one can make with those ketone measurements. I'll try to buy one soon
  34. Adam

    Here's the scientific effects. There is also a very interesting discussion of the surprising benefits of stevia:

  35. Jim
    As I understand it, just thinking about food & drink will release insulin. This experiment should be repeated using sparkling water as a control, maybe with some coloring in it so the brain thinks it's getting cola.
  36. Charlie
    I'd definitely like to see more tests like this one, with black coffee, flavored water, fizzy water, etc. Would be awesome if you did those tests!
    Reply: #87
  37. Steve Bergman
    Why wait and hope for a single person with very well known bias to perform the experiments, using consumer grade equipment, and acting as both sole subject and experimenter, when there is a whole body of literature out there offering information from properly designed and executed experiments?

    Sure, garage-science can be fun. But it's no substitute for the real thing.


  38. Nicola
    Interesting but not very scientific.
    You only did the test once so could be an anomaly. The LCHF diet and the fasting beforehand may have affected the results. There is also only one person doing the test so this could only be true for you.
    There might be something in your genetics or something that gives you a strange result. So I won't be basing any conclusions from this one test.
  39. Steve Bergman
    I'm not sure why some people seem to *want* to make LCHF more restrictive. One thing that has been shown over and over is that pretty much any reputable weight loss diet, even Ornish's, works *for people who follow it*. See Chistpher Gardner's ATOZ study for one example. One of the great strengths of LCHF is that it's *not* particularly restrictive. Disapproving of other people enjoying their diet sodas is *not* an excuse to try to fabricate baseless reasons they should not enjoy them. And if these results were valid (which they're not) that would be *bad* for LCHF because it would make it both less attractive and more difficult for people to follow.

    One other criticism of this anecdote ("n=1 study" gives these "experiments" far more respect than they deserve) is that it only tracks ketones and glucose. At no point does it ever measure how that may or may not translate to hunger or caloric intake. There's so much wrong with this anecdotal report that it's hard to know where to start.

  40. Jamie Hayes

    How easy is it to make a direct insulin measurement? You used the drop in ketones to suggest this. Also, it would be fascinating to see this experiment repeated with people who were not in ketosis, and especially in people who were overweight/obese. This might suggest whether the response is very different for different people.

    Plus, there may be a de-sensitising effect. As people drink artificially sweetened drinks, do they become de-sensitised plus dependent?

  41. Zepp
    Its not easy too measure insulin in blood becuse it have a halftime of some few minutes.. its only done in scientific laboratoriums what I know.

    But one measure C-peptide instead.. its a byproduct of insulin secretion and is more stable.. its then some sort of mean insulin.

    Easyest test of insulin response is to measure postprandial glucose levels.

  42. Jamie Hayes
    You mean that if blood sugar levels drop, you can assume that the Coke Zero has stimulated insulin, as what happened with the test that Andreas ran?

    It would be good to see the same test with an obese adult or teenager.

    Reply: #94
  43. Frances Lilian Wellington - Kinesiologist
    Hi Ken, the name "Frances Wellington Kinesiology" is my registered business name here in Australia, as I am a qualified Kinesiology practitioner. There are no spelling mistakes. I also use "Frances Lilian Wellington" to differentiate me from other people with the same first name and surname.
    Reply: #99
  44. Zepp
    Yes, thats what I mean.. but its more complicated then that.. becuse if glucose levels drops.. other mechanismes rises it.. like kortisol and other hormones that activates glycogenolysis!

    Soo one need to be in a real good laboratorium and measure a lot of parameters to realy know what happens!

    And then.. its gonna be different if one alredy hade high glucose levels or low.

  45. Linda
    This is not fair testing.
  46. Tara
    My two cents:

    I lost ~120 lbs on a LCHF diet, with innate insulin resistance from PCOS. The entire time I drank Pepsi Max like it was my lifeline. Now, that doesn't mean it doesn't disrupt things - heck, no N=1 can really PROVE or DISPROVE anything, but that would be my personal N=1 contribution to the discussion.

    Reply: #100
  47. MIke
    Can you run the test again, with Stevia by itself?
  48. Arthur
    Your ketones are diluted by any kind of fluid.
  49. Pete
    Presumably Ken meant that you used 3 'l's in Wellington (Welllington)...
  50. Donna
    I am new to this way of life and I am having a hard time giving up my diet pepsi. I dont think that I will be able to do so... So what all did you so to loose 120 pds, Because that is what I am trying to loose.... Please respond.... Thank you
    Reply: #101
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