Is Diet Soda Bad For You? The Science Isn’t Settled!

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Is diet soda bad for you? A new article says it makes you fat. But don't give up your diet drinks just yet. Image courtesy of and tiverylucky.

Is diet soda bad for you? A new article says it makes you fat. But don’t give up your diet drinks just yet. Image courtesy of and tiverylucky.

This week Time Magazine published a report on a new study that “links” diet soda to obesity.  Seniors (65 years old or older) who drank diet soda over a 9 year period “tripled” their chances of gaining weight around their belly than those who did not drink diet soda.

Of course the study’s writers called their findings “striking” (hmmmm….looking for more research dollars!).

No-calorie and low-calorie sweeteners continue to puzzle scientist about how they could cause weight gain. However Time points out that the answer may lie in the fact that these sugar substitutes actually sweeten diet soft drinks 200-500 times the sweetness of sugar. Yikes!

Allow Me To Get On My High-Horse For A Moment
I never liked diet soda. It tasted awful to me. Nope, my poison was regular soda. Specifically Coca-Cola. When I started this weight loss journey I completely gave up sodas and never thought to turn to the diet alternatives. Instead, I only drank water (tap or in carbonated form) or unsweetened ice tea. I’ve expanded my drinking list to include coffee (with 1.5 tsp of heavy cream).

The smartest thing I did was give up sodas. I think the stuff – diet or regular – is a slow death by weight gain. If you want to lose weight, water (and plenty of it) is your best beverage.

Dismounting from high-horse now.

But Is Diet Soda Really Bad For You? 
I do have a big issue with Time Magazine’s reporting. The study, published in The Journal of the American Geriatrics Society, is observational not a clinical trial. The reporter doesn’t question whether the results were correct? Doesn’t ask basic questions about the diet of the respondents in the survey. Or question if people should stop drinking diet sodas. Nope, the reporter treats what the writers of the study say as gospel. It ain’t.

According to Time, over a 9 year period, seniors were asked (every couple of years) how many sodas they drank everyday and to breakdown how many were regular or diet sodas.

Really? Heck I drank coffee today and I can’t tell you how many cups I had today, yesterday or on average since I started drinking the stuff in December…and I’m in my mid-40s.

There was no controlled experiment of diet soda drinkers vs. non-diet soda drinkers. What about these people’s diet? What were they eating? Could that cause the weight gain and not the diet drinks?

Oh, and Time left this kicker for the end of the piece:

“Researchers in the new study found that belly-fat gain was most pronounced in people who were already overweight…”

Hello Captain Obvious!

Because of this article people will cut or give up diet soda. While I think people shouldn’t drink the stuff, I don’t want that to happen because of bad science or bad reporting. And this thing smells bad all around.

I’ve learned a lot about bad nutrition science (and reporting of that science) during the last 3 years of my journey. The mother of all bad science was the low-fat craze promoted by the US government. Many nutritionists, researchers, shrinks, government officials and doctors stand by this crap even as a barrage of new studies, blogs and books shine the light on how flawed that original data was.

To be fair, I haven’t read the study. My guess is the PR person tasked with promoting the study over-stated the study’s data. And the researchers interviewed, also overstated its importance. Maybe they told Time that more research is needed to prove drinking diet sodas causes weight gain, but Time ignored it for the clickbate headline. Maybe, but I’m not holding my breath.


A quote from Dr. Helen Hazuda, the study’s senior author.

“…People who are already at cardiometabolic risk because they have higher BMIs are really in double or triple jeopardy,” Hazuda says. “When they think they’re doing something good by drinking artificially sweetened beverages, it’s actually totally counterproductive.”

Correlation doesn’t equal causation. This is an observational study and Dr. Hazuda forgot that observational studies only point to “links” or “associations.”  Her study cannot show that drinking diet soda’s causes weight gain. She has a hypothesis, that’s all.

But just because I think diet soda is unhealthy (and support Dr. Hazuda’s hypothesis) I can’t support studies and reporting that I agree with without stronger evidence. To do so makes me no better than those that support the bad data propping up the low-fat diet fad.

Until they take diet soda to a clinical trial (the gold standard of scientific research) I call BS on this study and Time Magazine.


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