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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.

Preparation

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

Low Carb Made Easy How to Lose Weight Low-Carb Recipes Low-Carb Success Stories

117 Comments

Top Comments

  1. 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?
    Read more →
  2. 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
    Read more →
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All Comments

  1. Donna,

    Remember that you don't have to give up everything at once. Why not keep drinking the diet pepsi for a little while longer and see you you feel a few weeks from now?

    In my opinion, "giving up" foods/drinks isn't what you do on low-carb. On low-carb you build strong, healthy eating habits, and sometimes you make exception to these habits :) Personally, I have 2-3 beers around two times a month. I know that isn't perfectly healthy, but as long as I do it rarely it's no big deal, for me at least.

  2. 1 comment removed
  3. Kanphong
    If I don't drink it after 5 hours, Will the ketone level rise back to the started number again? and how long time to rise back? I have drunk it 3 times in 6 hours, 10 ounces each.
    Reply: #104
  4. Personally I would not worry to much about that drinking Pepsi Max affects your ketone levels. But I have hard times believing that drinking Pepsi Max several times a day will add anything positive to your health.

    If I don't drink it after 5 hours, Will the ketone level rise back to the started number again? and how long time to rise back? I have drunk it 3 times in 6 hours, 10 ounces each.

  5. John Bedson
    As the blood sugar did not move, you can be certain that there was no insulin reaction provoked by the drink. Therefore no weight gain. The ketones probably reduced because the water in the (very large) drink diluted the blood enough to move the ketone concentration down. Ketones are only a tiny trace element in the blood, so a large drink will have a disproportionately large effect in diluting them.
  6. David
    Diet soda's..ugghhh. Why would anyone bother drinking something like this that tastes like crap and is full of man-made chemicals? I did try diet coke some years ago and put on 5kg in no time. Absolute rubbish.
  7. Mathieu
    I did the test with Coke Zero (more than 1L/33Oz). Measured with my Ketonix, it had no impact.
    Maybe all Diet beverages are not the same.
    Also I did it at lunch where I ate more than usual (LCHF soups), so I was bloated with soups and Coke Zero.
  8. Marcos
    I have a question. Ok, your sugar levels didn't change and your ketones decreased, so I'm not having Pepsi Max on a daily basis.
    But what about having a Pepsi Max instead of a glass of red wine during the weekends? Which one would impact more my weight loss?
    Thanks!
    Reply: #109
  9. Hi Marcos!

    Hi Marcos!
    I don't believe anyone have tested this scientifically. But my best guess is that an occasional glass of wine or Pepsi will not significantly impact your weight. :)

    I have a question. Ok, your sugar levels didn't change and your ketones decreased, so I'm not having Pepsi Max on a daily basis.
    But what about having a Pepsi Max instead of a glass of red wine during the weekends? Which one would impact more my weight loss?
    Thanks!

    Reply: #110
  10. Marcos
    Thanks for your reply!
  11. Frank
    My god this as bad as the food babe you know the one who said they put nitrogen in the air on airplanes very poor and non scientific.
  12. Helena
    What a pity you can't actually measure insulin at home. I wonder if your insulin level did go up as other studies seem to suggest might happen. Maybe because you are so keto adapted it wasn't enough to affect your blood glucose level but a less keto adapted person might have an insulin response and then a lowering of their glucose as a result of that? Just a thought.
  13. Scott H.
    I lost 15 pounds in 2 months drinking Pepsi Max.
  14. Gracie McGeorge
    Well I'm no scientist but I do know that when I chug a bottle of Pepsi Max or Coke Zero or other diet sodas my tummy is full (even uncomfortable) and thus I am not hungry. Helps cut down on total eating for the day as I do not feel like eating until dinnertime.
  15. Alfonso
    This is very interesting. I wonder though, did you drink the Pepsi without any food all day? If you ingested a LCHF meal and used one bottle of Pepsi to go along with it... would results be the same or would the fat slow the digestion or impact of the Pepsi?
  16. 1 comment removed
  17. Julia
    My thinking is that since ketones are produced when the body requires energy and burns fat to get it that perhaps the amount of caffeine in the sugar-free pop provided enough 'energy' during that short time frame that the body didn't need to find it from its own fat stores. I would recommend that test with a sugar-free / caffeine-free drink... And remember that Pepsi Max has twice the caffeine of other diet pops
  18. nancy
    so could you not just ingest an equal dose of sucralose dissolved in the same quantity of water as a test? this would control for the other chemicals, the carbonation etc and give some clearer results? that would be interesting to do. at any rate, I am convinced that artificial sweeteners cant be good for you period and am phasing them out of my diet.
  19. 1 comment removed
  20. Cathy
    What about Zevia, made from the Stevie plant, all natural, no coloring or anything?
  21. Linda
    I believe your Pepsi Max experiment may have some flaws because it's clear you state the artificial sweeteners did not cause weight gain, but the individual's desire to consume more food in excess of his/her regular meal. There is your weight gain,

    You also stated that if the artificial sweeteners weren't the cause of insulin production, then you surmise it must be the caffeine in the soda, but your next experiment will be coffee. According to Dr. Robert Atkins' Diet Revolution, circa 1972, he clearly states that caffeine consumption should be limited to two cups a day due to its ability to stimulate insulin.

    I don't believe artificial sweeteners cause weight gain, I believe people cause their own weight gain as it is iIlogical to consume a zero calorie additive that results in a caloric result.

    I am not in the medical field. The only proof I have is my own use. I have used artificial sweeteners for over 30 years live a low carb lifestyle. I have not experienced any I'll affects from Splenda (I use Splenda sparingly due to its fillers and that does slow weight loss), sucralose (EZ Sweetz) and Erythirol and neither cause me to overeat.

    Good luck with your caffeine experiment.

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