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. Your tests are always interesting and teach us something new! I'm definitely sticking with SweetLeaf Stevia which does not contain any articial sweeteners and does not alter blood sugar levels. I've experienced problems with sucralose, maltodextrin, sugar alcohols and aspertame in times past...
  2. I think we need another test run with carbonated water.
    Maybe it's not the caffeine?
    Maybe it's not the artificial sweetener?
    but possibly the carbonation?
    Does carbonation affect ketones?
  3. Greta Kirkland
    I started using Sweetleaf Stevia in my coffee, and I had to stop because it was effecting my weight loss. As soon as I stopped the sweetleaf and went back to the "stevia in the raw" packets, all was well.

    Thanks for the experiment!

  4. NM
    Judy, by mentioning blood sugar, you show you either didn't actually read this article, or didn't understand its most basic message. His blood sugar wasn't affected, but there is a suggestion that insulin was released, which slowed ketone production.

    For all we know, stevia may do exactly the same thing. Indeed, I suspect it does: studies have shown that it "improves" blood sugar, which probably means that it silently boosts insulin production without the usual concomitant glucose

  5. Katie
    Pepsi Max?? it's not only bad for your weight, it's bad for your health in aluminum can full of chemicals!? Drop a nail in it and it will dissolve within 24-48 hrs! I do appreciate your research.
    Reply: #62
  6. Sean P.
    The results from this test only tell us either:
    a) The artificial sweetener caused the response
    b) The caffeine caused the response
    c) The ultra-palatability of the food caused the response
    d) There was a placebo response because he expected (or wanted) something to happen
    e) The anticipation (and expectation) of receiving food caused the response (so it was nothing unique to just the soda but any food source)
    f) One of the other hundred chemicals in the soda caused the response.
    g) One or more of the above interacted together to elicit a response that would not otherwise happen if each individual component was tested individually

    With the exception of d and e, you could still make the conclusion that drinking a Pepsi Max would elicit some form of response but it's impossible to pinpoint the causal factor. However, it's also impossible to know if the response wasn't caused by d and/or e so it's impossible to interpret the results and find the causal agent and you definitely can't conclusively say the response was caused by the Pepsi Max (let alone blaming some singular component of the Pepsi Max for the response).

    Nice self-experiment though, I'll probably repeat something similar on myself soon but I'll test only once but I'll repeat the test once every three days for ten total tests to see if the response is the same every time. That way i can hopefully eliminate any non-physiological responses.

    As a better future experiment, you might want to consider just mixing artificial sweetener with water, and then combining pure caffeine with water, and then have a control (pure water) and then possible even have a mildly salted water to hopefully rule out any response due to the taste.

    Reply: #63
  7. Your blood sugar stayed constant - doesn't that imply that no insulin was released? I thought high insulin would always result in lower blood sugar.
    Reply: #8
  8. Sean P.
    Perhaps his body began releasing additional glucose into his bloodstream, which increased the amount of insulin in his bloodstream as well, and that insulin then did a good job keeping his blood sugar steady. The extra insulin then could be responsible for the reduced ketone levels.

    (Edited for clarity)

  9. John M.
    Andreas, this is very interesting, but I'd love to see at least one more experiment as a control. Maybe even with just plain water. Maybe just taking in any liquid causes your ketones to drop.
  10. SCMelville
    There may be reasons to avoid drinking Pepsi Max -- its ability to dissolve a nail is not one of them. Because it can't. Snopes is your friend:
  11. Trisha
    I love all the experiments & results. I've given up all artificial sweeteners except stevia pure powder - no additives. I'd hate to think I have to give up ever having anything sweet! :(
  12. Demosthenes
    Reference points required. We have no idea how the blood ketones levels behave under any other circumstance.
  13. It is very easy to criticise, but the idea of an n=1 experiment is not to perform perfect science, but to give some information which we can then think about. I very much appreciate any information like this as I try to adjust my diet for better weight loss. Having said which, my request for the next one would be black coffee :-)
  14. Thanks for sharing, I have long suspected a tangible negative effect from pepsi max. The fact that glucose does not drop appears to confirm my alternate hypothesis which you may want to consider in future tests.

    What if Pepsi Max is not triggering an insulin response, but instead is inhibiting the creation and/or retention of ketones. ie something about the bodys process of clearing out the chemicals is the root cause of the problem.

  15. Nadine
    I agree with Sean.
    It would also be interesting to do it on someone who is metabolically impaired or at least insulin resistant.
  16. wickedchicken
    Really interesting! Definitely gives us something to think it. This would be an amazing controlled research study (the relevance of sweeteners is so widespread). However, considering that most people are not in ketosis generally, what does this mean for the obesity epidemic in general? Could sweeteners silently be encouraging the storage of fat in non ketogenic subjects ?? (( if we presume it was the sweeteners, which is indeed a speculation))
  17. greg
    Yes, do it with coffee, and do it again with "sugar" water, where (of course) the sugar is just your favorite artificial sweetener. Please!!
  18. Patrick
    This is good information. I've been low carbing for awhile, lost over 30 pounds and seem stuck. I'm certain the culprit is the diet coke which I haven't successfully been able to give up. I don't know what evil genius created that stuff, but it's quite addictive.
    Reply: #49
  19. HighlySkeptical
    Isn't this pretty much what Lustig argues should happen? We know from that study last year that diet soda drinkers also gain waist circumference despite the "no calories."
  20. Hope
    I think the caffeine issue is pretty simple to do--test with Coke Zero or some other no-caffeine artificially sweetened beverage. For that matter, perhaps try Sprite Zero because then you'd also be without the caramel colorings that are in all "dark" sodas. That's the only way to really find the culprit.
  21. I was going to ask the same question as Martinus:

    If your blood sugar did not drop, wouldn't that imply that insulin was NOT released?

    Fascinating test though. I look forward to seeing your results from black coffee.


  22. Peggy Holloway
    I go with the insulin theory. I can't prove it, but when I started having strange mood/energy swings coupled with weird symptoms of shakiness, stomach gnawing, and light-headedness way back in my late 20's, I had a glucose tolerance test because of my family history of "diabetes." My ex-husband was a young internist who firmly believed in the carbs are good, fat is bad paradigm of the late 1970s, early 80s and called hypoglycemia a "crock disease." According to him, the results showed that my symptoms were not related to my blood sugar levels. Over the years, I have come to believe that it is insulin spikes that cause my jittery/hyper symptoms. Since going low carb, I rarely have those experiences. I did have the symptoms the first time I drank a Zevia soda and I have avoided all artificially sweetened soft drinks ever since. I am now in ketosis and love my steady levels of energy and physical stamina.
    Reply: #51
  23. chris
    Yes I'd love to see how this experiment would do with coffee, or someone mentioned here the carbonated water.. That would be interesting too, because I have not been able to loose weight on the LCHF and I'm trying to find the reason WHY. I drink both coffee and carbonated water (soda-water).
  24. Jeff
    I can only tell you that I switched to Pepsi Max as part of my better eating plan back last fall. Since then my weight has gone from 172lbs to 145lbs. I'm a 50 year old male 5'7". I've been holding at between 145-148 since June. That's my test!
    Reply: #25
  25. David Hogan
    Switched from what?
  26. Brad
    I dropped a nail in a can if Coke and a can if Pepsi and not only did it NOT dissolve, it did not even come out shinny.... Crock of beans...
    I read an article that stated thinking if something sweet can lower your keytones... Maybe it is mind over matter...?
    Reply: #56
  27. Brigitta
    I agree with Ted Hutchinson on this one. More specified testing should be done.
  28. gallier2
    Andreas is not diabetic. This means he has a properly working metabolism. The effect of insulin is not binary. It has several effects which depend on the concentration of insulin in the blood. The first effect is to inhibit lipolysis, long before it does anything to blood glucose. When the concentration rises, then the effect on glucose starts. When the concentration is going higher it will intensify the effect on glucose uptake and will also start to have a higher effect on lipogenese. In between, insulin at certain concentration will even have an effect on satiaty (logical, higher insulin means you've eated).

    What we observe here (my WAG) is a slight increase in insulin, enough to inhibited lipolysis and ketogenese. The very light glucose drop can be compensated easily by the liver (blood glucose level is primarly handled by the liver+pancreas). To do that a little bit of glucagon and cortisol are necessary. This would also explain Lustig's observation HighlySkeptical brought up above. Stress hormones (cortisol) tend to do that, deposit fat around the middle.

  29. Bjarki Gudlaugsson
    Do you think that Splenda has the same effect as aspartame?

    I just made some ice cream during the weekend from 3 eggs, 4dl cream, 1tsp vanilla and 1dl splenda and my weight went up about 2 kg from Saturday to Sunday. Some of it might of course be water retention because I feel really bloated after this but my weight has been going down rather steadily up until this point.

  30. Megan
    I am no expert, but, couldn't this have more to do with the stress on the body produced by drinking chemical water? As mentioned above, your liver is needing to process high quantiles of artificial sweeteners, colours, caffeine and preservatives. Couldn't this have a long term (a few hours) effect on the way we process our next meals. Perhaps this shows up as a ketone drop.

    There must be more to it than simply an increase or decrease in blood sugars.

  31. Doc could you please do this with lightly stevia sweetened tea? would really love to see the effects.
  32. laura
    Dear Doc
    If as you suggest the artificial sweetener had triggered a spike of insulin we should see a dip in your blood sugar level as well as the ketones....Something else is at work here although the effect on ketones is indisputable.
    You have set yourself quite a task now as you need to disentangle the various things that might be causing this.
    Also assuming it is the sweetener is this effect reproducible for different types of sugar substitutes? Are some better or worse for you etc? we ponder on!!
  33. Justin B
    I'd also like to see the coffee test, the sparkling water test, and in addition, the Splenda test, and the stevia test. What if its specifically the Ace-K causing the ketone drop? Or the Aspartame?
  34. Troy Wynn
    Hey Doc.

    Don't you need to repeat the experiment several times? You know, validate the results? Of course, under the exact same conditions!

    my 2 pennies!

    Reply: #40
  35. Oly
    1. An insulin test in addition to the ketone meter would be nice. :-)
    2. There's no way to know how much of it is due to the artificial sweetener without eliminating the caffeine. Atkins 101 is to go caffeine-free --- it is related to sugar dumping, stress hormones and sleep quality. And to head off all the belly-aching I can imagine hearing; it is not the end of the world to go caffeine free...actually it's wonderful to be caffeine free...better sleep and waking up energy filled. Then when you really need the stuff it actually *works* -- like when you have the flu or an emergency or to sustain extended exercise.
    3. Atkins still made you count your artificial sweeteners as carbohydrates and rightly so. 1 carb per packet.
    Reply: #58
  36. Sherry
    Interesting. Do you thing all artificial sweeteners have an effect? I recently bought "Swerve". Do you know anything about it?
    How about stevia and xylitol? Am I sabbotaging my weight loss by using these for an occasional dessert or sweetener in tea? What sweetener would you use? Also, did you eat anything else during this test?
  37. JaceB
    Finally, a real reason not to drink diet soda! Now if you can get 50 more people to do the same experiment! Can't wait to see if you have the same response to caffeine or aspartame alone. I suspect that you'd also find a similar decrease in ketones in response to fiber. I had a heck of a time getting into ketosis just because I added konjac root to my protein shakes. I guess I'll have to test that myself, using your methodology.
    Reply: #41
  38. One of the things I like about LCHF is that the explanations fit so much better with what I experience myself, than any other nutritional theories I've seen. However, the generally negative statements about diet soda has always grated with my own experiences. To me personally, there is one thing Pepsi Max do that no other diet soda I've tried does, and for some reason no-one seems to discuss it; I feel fuller drinking this soda, that I do with any other. (These others being Diet Coke, Coke Zero and Diet Pepsi.) It therefore seems obvious to me that some substance only found in Pepsi Max is doing something unique to my metabolism.

    However, I can't square my own experience (increased satiety) with the explanations given. I find an insulin reaction difficult to fit into this context, and that's why I hope you can expand on any explanation you suggest for your measurements, to also cover this unique effect on my feelings of satiety.

  39. Research into Type 2 Diabetes and Insulin might give us some insight into this outcome also. I found that pretty much any unnatural (manufactured) food or drink wreaked havoc on insulin levels and caused the body to go into a state of adaption. High insulin causes the body to store fat. Something to consider.
  40. He's not publishing this in a medical journal, so no.
  41. If you care about the results for you, then *you* might consider experimenting on yourself. Do you really want to deny yourself a source of calories on the basis of what my body or someone else's body does?
  42. I was going to say about the caffeine, because when I drink caffeinated beverages I wind up feeling more hungry later regardless of whether that beverage is (artificially) sweetened or not. So I'd like to see those black coffee numbers. But Fresca and non-caffeinated, sweetened beverages don't do that to me that I've noticed.

    And then you can drink some artificially sweetened water or something and compare ALL the numbers.

  43. Tia
    Now we know how this part of Doc' s metabolism worked on this special day and in this moment, nothing else. We cannot even draw conclusions that it would be the same tomorrow.... this is only n=1 and not science. Only my 2 cents.... :-)
  44. Michael
    Was it statistical significant? I don't think so. I would run a statistical test over the data before I can make a statement

    Although your ketone levels dropped at about 48% it doesn't imply that you were kicked out of ketosis because your lowest level was still 2.2 mmol/L.

    More of somethink doesn't automatically mean that it is better ... As long as you are in "the zone" ( 1.5 - 3 mmol/L) I would care.

    I think the idea regarding carbonation and its effect on ketones is very interesting. But I don't have any data if oral doses of carbonic acid do effect blood ketone levels + mayby art. sweeteners work as bases ...

  45. HighlySkeptical
    There's really no need for Doc to do all this a bunch of times - the study's been done in Texas. The "SALSA" study done by Dr. Helen Hazuda ( done on European-Americans and Mexican-Americans showed a strong association between significant visceral fat gain & diet soda drinking in about 500 people. She presented this research last summer to the ADA.

    "Epidemiologists from the School of Medicine at The University of Texas Health Science Center San Antonio reported data showing that diet soft drink consumption is associated with increased waist circumference in humans, and a second study that found aspartame raised fasting glucose (blood sugar) in diabetes-prone mice.

    “Data from this and other prospective studies suggest that the promotion of diet sodas and artificial sweeteners as healthy alternatives may be ill-advised,” said Helen P. Hazuda, Ph.D., professor and chief of the Division of Clinical Epidemiology in the School of Medicine. “They may be free of calories but not of consequences.”

    Emphasis on that second study: aspartame raises blood sugar in the insulin resistant. The smart money's that other fake sweeteners will do the same, and Lustig has offer a plausible mechanism.

    Reply: #59
  46. I would like to see this re-done with water + stevia. I have a suspicion the caffeine is doing something.

    I dont think it is due to insulin because the mechanism for insulin secretion involves closure of ATP-sensitive potassium channels which itself is dependent on increased intracellular glucose concentrations so in order for artificial sweeteners to secrete insulin they need to cause increased glucose concentrations in the beta cells.

  47. Jillian
    Hello Dr. Andreas. Thanks for the thought provoking post. I'm curious to know whether or not you have done the same test with another 'healthy' food? What typically happens to ketone levels with any food intake if tested like this? (Although with a liquid food such as this to me it would be logical that the results would happen more quickly than a slower digested whole food.)
  48. LowcarbNY
    An experiment without a control is just an anecdote.

    And a sample size of 1 is as small as you can get.

    So, while I find your comments interesting they can hardly be considered as supported by any science or data.

  49. Patrick, it sounds like your "setpoint" that your brain says "is the preferred weight for you" (+/- 5 kg) is ready to be adjusted downwards. Go find a Kinesiologist who is a Weight Loss Consultant to facilitate this for you.
  50. eric
    I agree with John M above: a control is needed!
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