Monday, October 7, 2013

Diet soda causes weight gain?!

What do you think? Does drinking diet soda cause you to gain weight or not?

Too much diet soda?
This is an old story; the media has summarized some studies done several years back concluding what many of you might fear—something with no calories can make you gain weight. But a look behind the sensationalized headlines showed something else.
Yes, there was a link; more people who drank diet sodas were higher weight. But did drinking diet soda cause it? And were you able to take in this correct conclusion and hold on to it, or do you still fear diet soda?

Oh, this is dangerous. I am not advocating for diet soda consumption! There’s no nutritional merit—no calories, no vitamins or minerals—and it may even have some negative effects. Namely, it may mask your hunger, making it more difficult to trust your need to eat. And large intakes of colas—regardless of type—may pose other consequences such as impacting your bone density

But really my intent was not to discuss diet soda. Rather, I’m highlighting this example to prove a couple of points.

Causation vs. correlation

Wasting way too much time on Facebook the other day, a post by a local, experienced dietitian caught my attention: 

Very interesting research about vitamin D's potential for significantly slowing MS. Adds to the body of research linking higher vitamin D levels with reduced risk for MS.
The comment was, on the one hand, harmless enough. The dietitian was referencing a recent article—just an abstract, really— presented at a recent medical conference. The abstract summarized the study findings fairly, stating that average, baseline blood levels of vitamin D link with disease symptoms and severity. Those with a lower average level of vitamin D at the start of the study had a worse disease outcome than those that started with higher blood levels.

This may seem subtle to you, but it’s not to me. The RD’s comment about the “potential for vit D to significantly slow MS” is not, in fact, what the article stated. It merely showed a connection, a correlation. Perhaps there’s something about people with MS that utilizes more vit D when there’s more active disease. Or maybe low levels are simply a marker for more disease activity. 

Nowhere did the study state that supplementing with vit D improved the prognosis. I don’t tend to look at the half empty, but I simply didn’t see the hope for vit D’s potential, at least not in this study.

Maybe it’s splitting hairs. I mean she did, in fact, refer to this as a link. But what troubles me—along with the image on the post showing supplements, is what’s implied and therefore what we end up believing. No, vit D supplements have not been shown to reverse or improve the health of those living with MS. But wouldn’t we all like to believe that a magic pill could do that for us—for our MS, for our cancer, for our anorexia, for our weight struggles?

But besides the false hope, there’s the issue of our getting sucked into believing that correlated equals caused. No, diet soda doesn’t cause obesity. But those living with obesity may be more likely to select diet beverages than those who are average weight.

Similarly, maybe you gained a lot of weight when you moved from a gluten free to a regular diet. That doesn’t mean that non gluten free diets cause weight gain. Rather, it may be that while being mindful of your intake—like you do on any diet—you may have seen a weight shift—but not because of what the diet was. But then when you regain the weight, you cling to the belief that the gluten free (or carb free, or fat free or whatever diet) was the reason for your weight loss, and therefore subsequent regain. The regain may have been about overeating following deprivation from denying yourself foods you enjoyed—and not a result of some magic involved with the ingredients you omitted.

Unfortunately, misinformation sticks. And trying to scream and shout that information is wrong only solidifies it as fact.  Misinformation can be dangerous, keeping us stuck in our ways, and preventing us from trusting ourselves. And conflicting info in the media confuses us and leads us believing that nothing we do makes a difference.

So instead, I ask you to question what you read. And challenge educated individuals in the health field about the articles and flashy news snips.

Focus on the facts, and work with your team for concrete ways to counter your unhealthy thinking. I hope this blog helps to set you on a healthy path!


  1. As someone taking a statistics class (and hating nearly every minute) I can say that I have learned you can state the statistics for something any way you want to argue a point that usually isn't really there. Assuming one thing causes another based on the statistics isn't often very wise.

  2. This blog HAS helped set me on the right path. You've given me the courage to simply eat sensibly, keep being active and quit thinking about the number on the scale. Thank you!

  3. There is SO MUCH information out there, each bit contradicting the previous one. Sometimes it seems better not to listen to any of it. Of course, thought, one should always listen to their RD!

  4. No matter what, it is undoubtedly unhealthy.

  5. What about research that demonstrates that consuming sweet-tasting non-caloric foods can disrupt satiety hormones and lead to increased consumption?

    I must admit it's really disappointing to see diet/nutrition and behavioral advice coming from people with weak backgrounds in scientific research and with shallow knowledge of the relevant literatures. That leads to the public distrusting research (see Anonymous comment above for an example) because they get the wrong impression about what is known and how/why it is known.

    1. NPR did a well-balanced piece on this: What is clear is that the evidence is not there to say that diet soda CAUSES weight gain. Correlates, sure.