23 March 2010

Diet drinks make you fat and give you diabetes?

No, not the name of the latest teen-pop sensation, but a perfectly valid hypothesis that I have been kicking around for a while. How many people try to lose weight, thinking that just having a drink of Diet Zingo might take the edge off their hunger, and help them get that satisfying sweet taste, without the risk of piling on the pounds?

Well, think again.

It could be that artificial sweeteners are actually making you hungrier, making you gain weight, and predisposing you to type 2 diabetes. Diabetic clinics are full of people who swear they don't eat much, and only drink diet drinks. Is it time to reverse cause and effect?

I stress that this is just a hypothesis at this stage, but it is way testable, and I hope to get around to exactly that at some point in the future. But here is how it goes:

1. You feel the need for a snacquette. You're hungry. You crave something tasty.
2. Aha, you say, I know - I will take a slug of Diet Zingo, which will satisfy my thirst and my sweet craving, and since it has only 1 calorie in 1500 cubic metres, I don't need to feel any of the crushing guilt that silly people complain about every time they eat one too many lentils. So, with a sense of utterly illogical and pointless moral rectitude, you knock back a few mouthfuls of the tasty aspartame-laden concoction.
3. Meanwhile, your brain (should you actually *have* one) is doing something rather interesting. Upon the sweet sensation, it engages in a very interesting phenomenon known as Cephalic Phase Insulin Release (CPIR). The sweet taste sensation actually stimulates the release of insulin into your bloodstream. The adaptive biological explanation for this is of course that it is getting ready to absorb some calories, and if you're primed with some insulin beforehand, this will prevent you getting hyperglycaemic, and will also get you metabolically ready to use or store those calories...
4. ...except the calories never come. It's *Diet* Zingo, remember? Virtually no calories. Oh dear. What is the insulin going to do now?
5. Well, it's going to act to drive your blood sugar even lower. What glucose *is* kicking around in your circulation is sequestered from the blood stream and converted into glycogen or fat.
6. In your lowered blood-sugar state, you get hungrier, so you either eat something, or you drink some more Diet Zingo, making the effect worse.
7. Your body thinks "oh crappo - I'm actually *starving* here", so reduces your metabolic rate; processes antagonistic to insulin kick in to rectify the blood glucose (still at a lower level than optimal), so you get even lazier, and burn off even less energy than before. This results eventually in insulin resistance.
8. You get *fatter* and more likely to develop type 2 diabetes.

The solution? AVOID diet drinks like the plague, unless you are eating something along with it. Nature cannot be fooled. Or, rather, if you try to buck CPIR, it will come back to bit you in your enlarging butt. There are no "good foods" or "bad foods" - just foods, and it is the pattern of consumption that is important. AVOID the lure of the sweet *taste*. CPIR is your enemy here.

And if you are an academic endocrinologist interested in carrying out a large prospective study on this, get your people to contact my people, and we'll do lunch. We'll be drinking tap water.


  1. Reading this, I remembered a presentation at ENDO in Washington last year that suggested this too. There have been other studies that back up your theory but this is the only one I could find quickly: http://www.medscape.com/viewarticle/704432

    (A budding academic endocrinologist)

  2. And here I thought diet drinks were just keeping people in the habit of eating sweets.

    A lot of people just don't count the calories in liquids like their Giant Slurpies or Coffee Concoctions.

  3. Hi Mona, yep, but the kicker here is that even if your liquids are lo-calorie, if they're sweet, they'll still alter your metabolism in a harmful way, making it harder to lose weight. The answer: H2O! :-)

  4. Hi Shane. Interesting theory, but at least one study has found that aspartame does not trigger CPIR. http://www.ajcn.org/content/82/5/1011.abstract

  5. Yes, can you please cite a report/study that links "sweet sensation" with CPIR?

    If insulin is released by the sensation of sweetness, this would be a good theory. But I think your assumption needs proving, first.

  6. Hi folks, thanks for the comment - good points. Paul - I checked that ref, and yes, it does seem to support the idea that CPIR is not triggered by aspartame. Other studies do show saccharin triggers it though. What is *really* needed here is a proper real-world study of what happens when you drink the drinks, not just getting a taste on the tongue, then spit. Modelling actual intake patterns. It's actually somewhat surprising that so few studies appear to have been done on this!

  7. Interesting post! This research team have studied diet drinks and weight for years and keep concluding that there is a link, but they don't say what. I think more should be done to tease out lifestyle factors and attitudes that might explain the findings, which are counter-intuitive. I've written a bit more about it on http://www.diabeteschoices.org.uk if anyone is interested...

  8. Thanks Christine - I think there's more to all this than meets the eye. In particular, I think we need proper studies in the NIDDM population and other groups.

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