Diet Sodas and Weight Loss. Whoops!

Ah the plot thickens.

We’ve been hearing buzz for years at nutritional conferences about diet soda. Not just the fact that it’s loaded with aspartame which no smart nutritionist I know of thinks is a good thing. No, it’s even worse. We don’t think the darn things help anyone lose weight. In fact, they may even have the opposite effect.

As one of my very politically incorrect clients once blurted out back in the 90’s, “Go to Disneyland and look what all the fat people are drinking: Diet soda!!!”

OK certainly unscientific, but new research is emerging that tends to back up that crass observation. Sharon Fowler, an epidemiologist from the Unversity of Texas Health Sciene Center at San Antonio, recently presented research about soda consumption to the American Diabetes Assocation. Here’s what she said: “What we saw was that the more diet sodas a person drinks, the more weight they were likely to gain”.

So why does that happen?

Three possible explanations. The first- what a friend of mine calls “the grab the low hanging fruit” explanation- is the easiest, simplest and most obvious. People who drink diet soda fool themselves into thinking they’re taking in less calories so they can eat more food to make up for it. The diet soda is their penance for OD-ing on supersize foods. People who overeat in general, the reasoning goes, assuage their conscience by washing down their 4000 calorie meals with a Slurpee-sized Diet Coke.

OK, maybe. But there are two other explanations which are even more interesting- both of which, by the way, can co-exist quite nicely with the first.

The first explanation is one that Mike Eades and I discussed a while back at a conference and it goes like this: Remember Pavlov’s dogs? If you happened to miss high school biology, the deal was that Ivan Pavlov, a Russian researcher, would ring a bell whenever he fed his dogs a steak. After a while, the mere ringing of the bell would cause physiological reactions in the dog like salivating, even when there was no meat to be found. I’ve long believed- and I think Mike agrees- that the same thing may happen with sweet tastes. Our bodies normally secrete insulin when we eat high carb foods, especially high sugar foods. Theoretically shouldn’t produce insulin in response to a zero calorie food like diet soda,but who knows? Maybe we're just like Pavolv's dogs in this regard and similarly conditioned: sweet taste comes in, pancreas says, "whoa, dude ate a ding dong, let’s get busy!", and releases a nice shot of fat storing hormone insulin, particularly in susceptible people?

That’s one theory.

To understand the second- even more fascinating theory, ask yourself this: why don't animals don’t get fat in the wild? Hint: it’s not just because there’s not enough food around. Even when there’s plenty, they don’t overeat. Why? Because their brains are well conditioned to associate food with calories (energy). It’s not like their little brain does a calculation and they say to themselves, “Hmm, this caribou is pretty high calorie, better cut back on the fatty part or I'm gonna have to do extra time running on the Savannah tomorrow”. Rather, the finely tuned and highly complex mechanisms of appetite and satiety are self-regulating, and ,one of those regulatory forces depends on food and calories being found together, as they always have been in nature. (Case you hadn’t noticed, there are no ‘low-cal” versions of zebra meat on the lioness’s menu plan).

So-- the thinking goes-- if our appetite and satiety mechanisms depend on an association between food and calories- if that’s one way we know we’ve had enough- what might happen when that association is artificially interfered with? As in when humans make diet soda? According to people who are doing research in this field, the mechanism may in fact break down. Accustomed to “thinking” (on a primal level, of course) that when we eat something sweet we’re taking in calories, our brains are befuddled. "What’s this stuff? I’m supposed to be getting energy from it, but there’s none there. Better keep eating!!"

Do we know for sure that this is what happens? No. We’re still guessing here. All the theories make sense, and all three may be operating at the same time.

What we do know is this: Diet sodas don’t do a darn good thing for you. And the irony is that they may be having the exact opposite effect of the one that you hope to get by drinking them in the first place.