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Does Diet Soda Lead to Obestiy?

People are always shocked when I tell them that I am a holistic health coach who drinks diet soda. They usually believe that my preference for diet soda means I actually have no idea how to be healthy. Today, I am going to put this myth to rest and show you that diet soda is, indeed healthy. Moreover, it can even help you live healthier, more sustainable and holistic lives. To know more about holistic health in general, check out this blog post “What is Holistic Health”. As far as today’s post goes, I’m going to be responding to a study that just came out here in China.

Recently, a friend forwarded me a photo of a doctor here in China. This doctor concluded that diet soda, while healthier than regular soda, led to increases in obesity and diabetes. Immediately, I pounced on this opportunity to react to these outrageous claims because, time and time again, the data has shown that this is not the case. For full transparency, I am going to show the original message, along with the translation of that message side-by-side.

original not translated
diet soda translated

The Confusion

While I haven’t read the doctor’s findings because they are in Chinese, I am sure that what he referring to is the correlation between obese people and diet soda. Yes, it’s true. Obese people tend to drink more diet soda. However, this is observational data, and we have to remember that correlation does not equal causation. I’ll repeat that again: correlation does not equal causation. You can correlate just about anything if you search hard enough. To show you how ridiculous this can actually be, take a look at this article that shows the 10 most bizarre correlations.

Anyway, there are two problems with correlating these two entities. First, it leads to misinformation for the public, especially because it is a doctor perpetuating these claims. Second, is this idea of reverse causality and that is what might actually be going on here. In this case, is it the fact that diet soda makes people more obese? Or do obese people drink diet soda more often because they are trying to lose weight and get healthier?

Do you see how this is an issue?

Randomized Control Trial Studies

To solve this, we need to look at randomized control trials. These are the gold-standard when it comes to research data. It just so happens that there was an awesome study done in 2016 by Peters et. all where they took over 300 participants and split them into two groups. Researchers asked one group to refrain from all artificially sweetened beverages. Moreover, they needed to consume 24 ounces of water every day. Researchers had the other group to consume the same amount of diet soda every single day. 

What’s really nice is that this study was really well controlled. Each participant was scheduled to go to monthly meetings. They were given the same kind of nutritional information there and were weighed. And they received the EXACT SAME instruction. That’s important to note. To control for calories as best as they could, they took each individual’s BMR and multiplied it by 1.6 putting them into an equally proportional calorie deficit. Also, researchers made sure participants did the same amount of exercise and activity. There were two phases to this study. One phase was a weight-loss phase consisting of twelve weeks. The other phase was a 40-week maintenance period to see how well they kept off any weight that they might have lost. The only difference is that one group drank ONLY diet soda and the other group drank ONLY water.

If Doctor Chen Wei’s hypothesis about diet soda creating a sweet craving and making you want more food was actually accurate; or that it’s somehow increasing your insulin so you’re going to store fat regardless of caloric consumption; or if it somehow disrupted the gut microbiome which messed up your blood glucose and insulin sensitivity and all that stuff. If any of those things were true, then we would expect to see that in this study after a year. But that never happened.

The Results?

The researchers thought that there wasn’t going to be a difference between the two groups, but there was. A big difference.

The diet soda group lost 3 more kg in bodyweight than the total participants. What’s more, they kept off more weight (2.5 kilos) during the maintenance period. So this is out of all 300 participants who started the study. That is the data for that. However, 223 of those individuals actually completed the study. This means they went to all the meetings and adhered to everything perfectly. Out of those people, there was actually a 5 kg difference in weight loss and better weight maintenance as well.

In fact, it was so amazing that the researchers had no idea what to make of this data. They were kind of dumbfounded. And, to be honest, I don’t really know either.

There is no data to support that diet sodas have magical fat burning properties. However, I have an idea of what might have happened. It correlates with what the researchers postulated. Because the diet soda group had some sort of sweet flavor in their drink, they didn’t desire further sweetness. Meaning, they didn’t seek out sweets in desserts or other foods. This most likely resulted in a lower caloric consumption despite the efforts in the researchers to control for this.

And, actually, during the course of the study, the only-water group reported being hungrier than the group who had diet soda, so it helps further along that hypothesis as well. You’ll see in the image below three columns and their hunger levels at the beginning, after 52 weeks, and their change. You’ll see the NNS group (the artificial sweetener group) reported feeling less hungry after the study and the water group had a significant rise in hunger.

diet soda and hunger

As far as blood markers go, there wasn’t any difference in those factors. Actually, the group that had the diet soda, the diet soda group had significantly lower blood pressure than the group that didn’t have diet soda. Again, this isn’t due to diet soda probably, this is due to the fact that they lost more weight. They lost 5 more kg than the other group.

Now if this was only one study, then I’d say that maybe this is just a fluke. However, this actually supports two more studies done that show diet soda leading to a reduction in weight. Blackburn Et All conducted a two-year study that showed, “the aspartame group lost significantly more weight overall and regained significantly less weight during maintenance and follow-up than did the no-aspartame group.”

Another six-month study done by Tate Et all showed “replacement of caloric beverages with noncaloric beverages as a weight-loss strategy resulted in average weight losses of 2% to 2.5%.”

tate et all study

Of course, feel free to check out these studies more for yourself; I have linked them down below at the end of this article. Before you go running for the hills, though, and grabbing your diet sodas, there are also studies that show diet soda had no significant reduction on weight loss, which is what is to be expected if calories are equated.

What I really think is going on, though, is that diet soda creates a kind of appetite suppressant effect. Sort of like coffee. We don’t feel as hungry when we drink diet soda, and thus we consume less calories. From my own personal, anecdotal experience, I know that diet sodas do tend to fill me up and I believe it is that carbonation in diet sodas that does this. Understanding this, if you are trying to lose weight, then diet sodas may be a very helpful tool in doing so.

In terms of being bad for blood markers and gut microbiome, this study would have shown something, but it didn’t. There isn’t one study done on humans under normal conditions that shows any elevated risk of cancer or diabetes or disrupting the gut microbiome. The studies that have done that have been conducted on rats in a lab where they give them a superfluous amount of aspartame that would be impossible to replicate in normal human conditions. And another study put a hefty load in a petri dish with ecoli to show that it disrupted gut microbiome, but again, too much of anything is a bad thing. Too much water is even bad for you. It’s called drowning.

I am not saying that you should drink diet soda. I am saying that if you choose to drink diet soda, then you cannot make the argument like this Dr. Wei made where it causes you to become obese or become diabetic. If anything, you can make the argument that it aids in weight loss because of the three studies that again I will link at the end of this article.

Again, this is probably just due to the fact that diet soda creates an appetite suppressant effect and so we consume fewer calories when drinking it. When we consume fewer calories, we eat less and thus lose more weight. That is as simple as weight loss gets folks.


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