What happens if you drink Pepsi Max?

Pepsi Max test

What happens if you drink Pepsi Max? Nothing if you believe the soda industry. Diet soda contain no calories, only artficial sweeteners (Aspartame and Acesulfam K in this case).

But when my friend Ronnie Mathiesen tested his blood sugar after drinking Pepsi Max it had a weird effect on his blood sugar (pictured above).

I’ve been planning to redo that test to see if I get a weird result too. Now is the time. And I will not only measure my blood sugar. As I’m in ketosis now I’ll also track my ketone levels closely. If artificial sweeteners result in release of insulin (studies show divergent results) the ketone levels should drop. Ketone production is very sensitive to insulin.

Ultimately this is not just about diet soda. It’s about whether common sweeteners (regardless of use) can somehow disrupt the regulation of blood sugar, insulin and thus mess with satiety, cravings and weight.

What do you think will happen to my blood sugar and ketone levels when I drink 500 ml (17 oz.) of Pepsi Max while fasting?

Update: The results


  1. Sue
    Brilliant experiment! Thank you for being the guineapig - looking forward to seeing the results :)
  2. I swallowed two tiny Aspartame tablets, after 30 minutes my blood sugar went up from 4.4 to 4.8 before falling back to 4.4 after 60 minutes. I stopped using any artificial sweeteners.
  3. Bob Johnston
    I've read studies showing Aspartame has no effect on blood sugar and insulin levels but there must be some effect on a body's metabolism because even though I was already low carb I dropped 14 lbs of fat and gained 6 lbs of lean muscle in 6 weeks after dropping diet sodas from my diet. I was a very heavy user of the stuff though, upwards of 200 ounces a day.
  4. Daniel FE
    what about Truvia?
  5. I was going to do this test myself as I was very curious...and Pepsi Max is really good!
  6. Stacy in USA
    I'll be very interested in your results. I occasional drink diet soda but haven't measured any effects.
  7. Peggy Holloway
    If you are insulin resistant, you will definitely see blood sugar and/or insulin spikes.
    The first time I tried a Zevia soda, I had all of the symptoms I get when I accidentally ingest hidden carbs. (I never consume carbs intentionally, with the exception of non-starchy veggies). I don't test insulin or blood sugar because my symptoms are so severe that I don't feel I need to. I experience a shakiness with an elevated heart rate, stomach gnawing, and a feeling like my skin is crawling within a few minutes of eating something that causes what I interpret as an insulin spike. Within an hour or two, I have a major "comatose" energy clash. The stevia- sweetened soda had that effect on me, so I assume that just the taste of something sweet produces an insulin release for me. Is there an easy, inexpensive way to test insulin levels at home? I am more interested in that than in BG levels. At my age, however, and with my family history, I am concerned that despite my current ketogenic lifestyle and 13 years VLC, my pancreas may still be suffering from the earlier havoc my high-carb diet wreaked upon it so I'm thinking about getting a meter. I don't have health insurance, so I'm not sure I can afford it.
  8. Fabian
    The changing of bloodsugar from the pepsi max seems negligible (it only looks impressive because the y-axes was changed). it would be great if you could illustrate if the rise really does matter. i drink a lot of pepsi light/max (~1.5l a day) and have no problem to maintain a BMI of 20. But of course i haven't tested my bloodsugar after drinking it...
  9. HighlySkeptical
    I think if you're the slightest bit metabolically deranged, your blood sugar will be weird. Because the body processes the fake sweeteners just like it does fructose. Lustig said this on 60 Minutes, didn't he? Normal people might not notice much; but almost no one has a normal metabolism any more, as Dr. Rosedale says.
  10. Oly
    It didn't happen in the beginning but eventually I got to the point where I realized diet sodas were unappetizing and would make my wedding band tight. Two sodas was about enough to make my bp go up 10 points and make my wedding band uncomfortable. Water retention just like eating carbs -- caffeine has bs effects too. One time of "settling" for it and I got a migraine-grade headache when I had some sinus stuff going on. My husband used to pound them like water for quite some time and eventually he said "I'm not going to drink that anymore" -- he felt jittery, anxious and bad. Now we humorously call those sodas neurotoxins .

    Body chemistry is so complicated -- seems like a bad idea to load up on an isolated compound. Best to get one's aspartate and phenylaline where God put it originally....where the cure is wrapped with the poison.

    I may not be able to explain the reason why it's bad -- but it doesn't mean that reason is nonexistent.

  11. Demosthenes
    You should use a caffeine free beverage.
  12. How is your fasting? Like how are you fasting? Well that cause ketosis?
  13. I'm still baffled as to how any kind of soda can be calorie-free, but there are many things aside from sugar that affect insulin and blood sugar balance. I'm anxious to hear about the results of this. In reality, anything that is not made by nature is a toxin in some way and will cause the body to adapt. Adaptation causes disease. This will be interesting.
  14. Can you do this with Stevia sweetened tea as well??Brilliant Experiment.
  15. Jane2
    I think that if you are fasting and drink it, the sugar level in your blood will rise. But if you are not fasting and you stay on 90% fat, your sugar level will not rise.
  16. Eleanor
    An engineer would call this a "damped oscillating response."

    It would result in more insulin production overall than the classic curve because of the re-spiking in the levels.

    Curious to see if yours will show the same tendency....

  17. Jillian
    I appreciate Dr. Richard K. Bernstein's suggestion if anyone is concerned about insulin levels--test, test, test your blood glucose levels to see how you respond to various foods (or sweeteners, or additives, etc.) because everyone is so very different. What will increase one person's insulin levels will not necessarily increase the next person's. They only way to really know is to test yourself...
  18. Diane
    I don't think you ever answered your last "what do you think happened" question. What actually happened when you went into ketosis? Can you write a post about the transition and how you felt once you achieved it?
  19. Eleanor
    Interesting ... if we assume the insulin is produced in proportion to the decrease in blood sugar levels, even though the blood sugar level was not that high to begin with (starting at 6.3 and tailing down to a mid-range 5.2) there's a cumulative decrease of about 3.3...

    Which would mean the overall insulin response/production would be similar to something which had raised the overall blood sugar to around 8.5, i.e. a little bit lower, but pretty close to the response to the bread & jam.

  20. Ken
    THANK YOU for doing this experiment.

    I have a hunch that diet soda is a player (maybe an important one) in the obesity epidemic.

  21. John Myers
    I'm shuddering with antici...
  22. Brad
    Try Splenda as well since it is quickly becoming the sweetener of choice...
  23. Nadine
    Cn you also test after something like greek yoghurt and berries? Something that doesn't taste sweet to sugar addicts but tastes like dessert to us.
    Reply: #26
  24. Wolfstriked
    Doc,could be adrenaline or some hormone being released that forces the liver to release a lot of glucose.I drink lots of diet sodas and can tell you that Pepsi Max is very high in caffeine and I feel a difference comparable to a large coffee.The up and down could be the insulin and resulting dropping of glucose effect.Then when the still high blood caffeine levels cause more glucose dumping from liver it spikes up and down.Might be worse to consume diet caffeinated sodas then since you get this up and down effect?

    Funny that my super ripped partner I work with tells me every time he sees me drinking a diet soda that he thinks they cause weight gain.Who knows??

  25. Wolfstriked
    One other thing Doc,any chance to guinea pig yourself for more than Pepsi max?I think testing regular coffee or even caffeine pills will rule out some artificial substance as the culprit.
  26. Great suggestion, Nadine! I am in nutritional ketosis and berries taste like Samrties to me now.
    Reply: #31
  27. Bill
    You lack a "control" in this experiment. The fluctuations in the readings from the Pepsi Max may have happened even if you drank distilled water; after all, the instrument probably has some level of normal reading variation. Test that by taking 10 or 20 readings within a few minutes and getting a range. For a control, drink an equal amount of water (as the Pepsi) at the same time the next day, after the same fasting conditions, etc.

    Fun and interesting experiment!

  28. Bret
    Drs. Mike and Mary Dan Eades said that insulin levels start increasing as soon as something sweet is tasted in the mouth. This mechanism sort of primes the bloodstream for the impending influx of glucose, rather than waiting to react until after blood sugar has risen above ideal levels.

    They discussed diet soda specifically to that effect, in that when you drink diet soda, you are indeed increasing your blood insulin levels simply from the sweet taste. I imagine 500 mL will do the trick. Looking forward to seeing the results.

    This was in a Jimmy Moore podcast a few years back, but I don't remember the episode number or exact date.

  29. Cat
    I am also curious about the effects of coconut palm sugar/gula java which is supposed to be "not so bad" for sensitive blood sugar types, I have some, it's expensive (aman prana brand with green tea and 1 with cocoa), it tastes a bit like rapadura to me which isn't so much sweet as it is molasses'y and mineral rich, but the only testing strips for diabetes I have are to be used on empty stomach first thing in the morning. If anyone happens to do a test using the coconut palm sugar I would be interested to know results.
  30. Sue
    Great comments - this has certainly got everyone's attention!

    I think the caffeine point is very valid as caffeine does cause an insulin response. I wonder what impact sugar free lemonade would have, for example??

    Also, the issue of sweetness is an interesting one as what tastes sweet to one person doesn't to another - I find diet Pepsi far too sweet to taste and can only drink it with a massive wedge of lemon. So there may not be a 'one size fits all' answer.

  31. Great suggestion, Nadine! I am in nutritional ketosis and berries taste like Smarties to me now.

    Agreed. Ironically, abstinence from sweeteners is the best sweetener of all - it sweetens everything!

  32. Jessica
    It would be great if those who are coming up with alternate things to test Would get a BG meter and test them themselves. The meters are not all that expensive, and I think a ton of interesting data could be gathered in no time.
  33. JAUS
    Watch this excellent Youtube video about artificial sweeteners: http://youtu.be/VUo2XW0z218
  34. SL
    So many variables

    Caffeine ? and/or artificial sweeteners? and / other ingredients ? ?

  35. Jessica
    I have a feeling the Pepsi Max will make you hypertensive as well (especially since you don't normally drink the stuff.)

    I'd be curious to see what happened if you drank it for several days instead of water. (Gross, yes, but there are hundreds of thousands of people who do exactly that, every day.)

    I think if you got your blood tested before the test, then did a week or two drinking soda in place of water, then got your blood tested again, you'd discover some pretty startling effects. (I'm betting you'd gain fat, see higher triglycerides, and your blood pressure would skyrocket.)

    I also think that, if you did such a test, your blog would get more traffic and links than you ever thought possible.

  36. Nadine
    You could make it a double blind experiment if you had artificial sweetener tablets or identical looking and tasting "nothing" tablets, if that was possible. And a larger group of people would help. Versus sugar would also be interesting!
    Reply: #37
  37. Tia
    How can you make it double-blind, if it does not taste sweet? ;-)
  38. Nads
    To Tia. Well that way you wouldn't be able to tell if it was the sweetened product or the non sweetened. But then again, if you are proposing it's the sweet taste that is causing a response it would be useless to have there being no taste. Good point in that case.
  39. I did a lot of research myself on this very issue because, like my father before me, I have a ravenous sweet tooth. He would hold the teaspoon under the sugar pourer, begin to pour, and count 1 - 2 - 3, dumping each full teaspoon into his coffee but allowing the sugar to continue to pour out. Would you like some coffee with that sugar?

    Anyway, I have lost 50+ lbs using low carb eating and some portion control. My sweet problem was and is solved by using Splenda. Every reputable scientific study has said that neither Splenda nor Equal (I don't use this because it gives me headaches) causes any kind of a spike in blood sugar.

    I decided to be my own guinea pig, so on a morning when I was fasting for a full blood analysis, I sweetened water with a boatload of splenda. Almost couldn't drink it! To make it even more skewed, I took some with me and drank it 10 minutes before my blood was drawn.

    Results? Not even a hitch in the giddy-up. Nada. And I had had borderline diabetes before I started losing weight. That changed with low carb dieting.

    Anyway, that's my experience, and if nothing else, Splenda has helped me cut down my sweet tooth. I drink no soft drinks anymore, have a couple cups of coffee per day (1 decaf) with three packets of Splenda, and I eat one Gnu Bar per day, covered with cream cheese (as per the good Diet Dr.'s advice).

    I also exercise more and hardly feel it. Walk, bike, play racquetball, dragon boat race, etc. I'm female and 58 y/o.

  40. I am new in this area of weight loss but when i made the decision to do so, i moved to low carbs diet and opted for Stevia sweeteners and diet sodas. In less than 6 months my BMI moved from just above 30 to 23. i consider this shift better than the indulgence i used to do on carbs. i have lost 15kg since then and continue to lose (significant amount of fat around my waist and already in good shape). I take about 2 cups of coffee a day and usually 1 cup of green tea at night all with sweetener. i often have diet soda on Sundays and when am out with friends or really craving for a drink. This to me is way better than the every day feast on carbs i used to do. Maybe this approach should be left to those who see it as an alternative diet, unless it is sabotaging their efforts in visible ways.. It can be very challenging at times to stick to a strictly no-any-kind-of-sugar diet, especially when you are a beginner. My encouragement would be 'keep away' as often as you can from them BUT consider these as your option should a need arise. just like fruit, moderation in everything is the way to take!
  41. JEFF
    Don't bother to do the experiment if you are going to use a caffeinated drink. It will only confuse the issue. On the other hand, if you use PEPSI without caffeine, it could be helpful. I would love to see how insulin release is effectef by the popular keto-grains ie. Flax, Chia, and Psyllium husk as everyone seems to be making bread-like products from them at home.
  42. Rhiannon
    Hey! I'd just like to say that as a type 1 diabetic, I found that drinking pepsi max would cause my blood sugars to drop, therefore I would have to eat something sugary afterwards, I think this is because caffeine is a diuretic. I know before I was diagnosed with diabetes I would drink like crazy because my body was trying to flush the sugar out of my blood, but I didn't have any insulin to convert the sugar into energy, so my body began to break down fat, and then muscleto compensate. But when my body broke down muscle, it would release these toxins called "ketones" into my blood. These levels of ketones can go dangerously high resulting in "ketoacidosis" But anyway, back to the point.
    I found that especially if I drink pepsi max between meals my blood sugars will drop, I think this is because there is nothing to keep my blood sugars stable. I'll go into the topic of G.I here, (Glycaemic Index)
    Something with a high G.I, (sweets, refined carbs, sugary drinks, jam...) Are foods which contain carbohydrates that break down quickly into sugar and raise blood sugar levels quickly, but will not sustain them, you will find that with high G.I foods and drinks your blood sugar will "spike" and then quickly drop again because the sugars have already been broken down and your body has released the adequate amount of insulin to cope with the dramatic spike in your blood sugars. This is why if you eat say, two pieces of white toast for breakfast, you have an energy slump and/or are hungry not long after.
    Things with a low G.I (Beans, porridge, Basmati rice) Contain carbohydrates which break down into sugar more slowly and provides a more sustained release of energy into your body. Low G.I foods produce a gentle rise in your blood sugar levels, so your body will gradually release insulin to convert the sugar into energy. Choosing slowly absorbed carbohydrates will help to even out glucose levels. Soluble fibre is also important, as it takes longer to digest and lowers G.I . This is why if you choose to eat say, rice, vegetables and a form of protein for dinner, it will sustain you for longer.

    This is why I don't agree that Pepsi Max actually RAISES blood sugar, but LOWERS it. My body doesn't produce insulin at all. It can't. The beta cells in my pancreas have been destroyed and I rely on injections of insulin to live. So I think that as pepsi max contains a lot of caffeine, and caffeine is a diuretic, the caffeine will actually flush out the sugar in your blood, causing you to have an energy slump, and then to eat something sugary or high in energy to compensate.

    That's what I think anyway! =)

  43. james
    Thankyou. I have found that a lot of fear mongering and bs is floating around re diet drinks. As a diabetic who got the disease due to liver function error.. and not by eating crap.. drinking pepsi max didn't lead me to gain weight as i didn't have bad dietary habits which got me diabetes in the first place, like most people. Coffee has a drastic effect. Sugar is bad, too much water bloats and i don't drink fruit juice. Pepsi max is good as it also keeps me awake some times as well when needed. A lot of the anti Cola forums are filled with people who have nfi what they are talking about or are copy paste activists.
  44. stuart bedford
    I am inclined to agree with Dr Atkins when he says that in doing a Glucose Tolerance test doctors leave it too long before they take a blood test after they have administered the Glucose. I find that the rush comes within the first 15-30 mins and having the blood test after 1 hour means that the rush has gone.
    Also, I was a heavy alcohol drinker years ago and I find that most men who discover that they are Alcoholics are actually Hypoglycemic, I know that I was.
  45. 1 comment removed
  46. Børge F
    I used to drink 3 cans of Pepsi Max a day.
    Still lost 55 kg in two years on a low carb diet. Still after a year kept weight ie added a litle due to training muscle and a litle fat.
    So I dont think it lead to weight gain or liver problems as I have taken full bloodtest yearly and all is welll.
  47. Michal
    I am a diabetic for 26 years already. I'm insulin dependent for about five years. Recently I have noticed after drinking Pepsi Max that my sugar levels become more normal instead of the high levels it used to be. I also have now for a while diarrhoea, so I thought I might find some answers here.
  48. Cassidy Smith
    Where's the results?

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