Is Your Diet Soda Making You Gain Weight?


Artificial Sweeteners Are Linked to Weight Gain and Other Health Issues

Why Caution May Be Warranted When Consuming Artificial Sweeteners

Artificial Sweeteners Again Linked to Weight Gain, Diabetes, High Blood Pressure

If you follow the news, are active on social media, or just have a keen interest in the latest breaking nutrition research, you’ve probably seen headlines such as these trending recently. That’s because a new study on artificial sweeteners has a lot of people questioning how safe your diet soda really is.

Do Artificial Sweeteners Harm Your Health?

The study set out to assess if regular use of non-nutritive sweeteners (also known as artificial sweeteners) was associated with long-term effects on cardiometabolic health.

The researchers compiled all of the latest research studies that looked at associations between artificial sweetener intake and markers of health including weight, metabolic syndrome, type 2 diabetes, high blood pressure, and any other cardiovascular or metabolic health related markers such as stroke or coronary heart disease.

They included both randomized controlled trials (RCTs) — considered to be the gold-standard in research design, and the approach used to show cause-and-effect — and prospective cohort studies, which follow groups of people over time to assess how differing factors (in this case artificial sweetener use) affect rates of certain outcomes (e.g., markers of health and disease).

The findings weren’t that clear.

For one, the findings from the RCTs and cohort studies seemed to contradict one another.

For example, the RCTs that examined  weight change saw either weight loss or no significant effect on weight. But the cohort studies showed an association between artificial sweetener use and weight gain.

Both types of research designs have their merits and challenges so, with such conflicting outcomes, it’s hard to draw any real, significant conclusions about the impact of artificial sweeteners on weight.

Cohort studies also showed some association between artificial sweetener use and increased risk for obesity, high blood pressure, metabolic syndrome, type 2 diabetes, stroke, and cardiovascular disease. But, again, these observations have not been supported or confirmed by RCTs. That doesn’t mean they are not significant, but it does mean more information is needed before definitive conclusions can be drawn.

The real take-away is this:  Existing research is not sufficient to determine the exact relationship between artificial sweetener use, weight, and overall health. Does it lead to weight gain? Does it contribute to the development of diabetes or high blood pressure? The jury is still out and we won’t have answers to those questions until we have a lot more research on this topic.

Headlines Rarely Tell the Complete Story…and Sometimes Tell A False One

But the way this study has been covered  in the media would lead you to believe that artificial sweeteners do cause weight gain and chronic disease. In many reports, the information from this study has been sensationalized at best and is totally inaccurate at worst.

We read “artificial sweeteners are linked to weight gain and other health issues” and we assume a cause-and-effect relationship — that use of artificial sweeteners of any kind and in any amount must be bad for our bodies and that we should totally eliminate them from our diets.

But that’s not what this study is saying.

I also read a media report that said, “all of the studies selected found that artificial or nonnutritive (zero calorie) sweeteners had negative impacts on the metabolism, gut bacteria, and appetite of the subjects.” That is just plain false.

Now, that is not to say that there isn’t evidence to support the idea that these products may affect metabolism, gut bacteria, and appetite, but that was not evaluated in this current study. This example sheds light on the overall importance of always, always reading media reports of research with a critical eye.

What You Need to Know About Artificial Sweeteners and Health

Suggestions that artificial sweeteners may be harmful to our health come from cohort, or observational studies. But these studies haven’t been confirmed by more rigorous randomized control trials. That means there are a lot of additional factors that could also be responsible for, or at least contribute to, what cohort studies suggest.

For example, who might be most likely to choose an artificially sweetened food or drink product? Perhaps someone who has a desire to lose weight or is trying to “control” her weight and is intentionally trying to restrict calories. Well, we know that restrictive dieting contributes to long-term weight gain. So, when a person who uses artificial sweeteners gains weight, is the artificial sweetener the cause — or the overall act of dieting?

This is called reverse causality and in studies such as this one, controlling for this can be really difficult, if not impossible.

It’s one of those, what came first, the chicken or the egg, situations. Is it that someone prone to gaining weight is more likely to choose a diet soda or that the sweetener in the diet soda itself caused the weight gain?

That also speaks to the important fact that correlation does not equal causation. Just because when we see artificial sweetener use increase, we also see an increase in weight or disease risk, it does not mean artificial sweetener use caused this increase. There could be a whole host of other factors to help explain this relationship.

To illustrate this point using another example, we also see a correlation between increased ice cream sales and increased rates of drowning. Does that mean that ice cream causes drowning? Of course not. It probably means that on hot weather days we are more likely to eat ice cream and we are also more likely to go swimming.  

Is Sugar Better than Artificial Sweeteners?

I think it’s so important to clarify what this study really tells us because humans tend to be very black and white in our thinking about food. As soon as we see a headline that says, “artificial sweeteners are linked to weight gain and health issues,” we often automatically conclude that regular sugar must be a better choice.

And, if we’ve been consuming excessive quantities of artificial sweeteners and now we switch to excessive quantities of sugar, that’s not necessarily better for our body.

In fact, another recent study also showed a correlation between artificial sweeteners and onset of type 2 diabetes. However, the association between sugar-sweetened beverage intake and type 2 diabetes was much clearer and much stronger.

The truth is that nothing is good for our bodies in excessive quantities. Not artificial sweeteners, not sugar, not water, not kale.

All of this commotion speaks to one of the major problems in today’s diet-obsessed culture. We’ve reduced the value of foods to their calorie content. High calorie = bad. Low calorie = good. No calorie = the best. When we think of a food as the “best” choice, we might find ourselves consuming a lot of it without thinking it could be problematic. In reality, it probably is.

Should You Use Artificial Sweeteners?

To be clear:

  • I am not saying that there isn’t any connection between artificial sweeteners and disease risk.
  • I am not saying they are more or less healthy than regular sugar.
  • I am simply saying, while it does provide sufficient evidence to suggest more research is warranted, this study did not show that artificial sweeteners cause weight gain or diabetes or any other chronic disease.

For most people, it is unlikely that weight gain or the onset of a chronic disease is attributable to a single food item or ingredient. It’s what we do collectively over time that has the most impact.

In most cases, drinking a diet soda, or consuming artificial sweeteners in any other form, on occasion, is not going to significantly affect our health if we have an otherwise fairly balanced and health-supportive eating routine. The same holds true for regular, sugar-sweetened soda.

So, if you are still wondering, should I be pouring out my diet soda? The answer is, not based on the evidence presented in this study. But, that’s not to say it isn’t worth taking a look at how much artificially sweetened food and drink you are consuming.  

And, it’s also worth noting that, it seems unlikely that artificial sweeteners on their own possess any health-promoting properties.

When it comes to health-supportive eating, the key is balance, variety, and moderation. It’s not sexy. It’s not novel. It’s not exciting. But it works.


Contact us to learn more about our 45-year old philosophy for sustainable health and wellness – without counting calories, boot camp work-outs, or restrictive dieting.

We’re here to guide you and give you tools to solidify your success at home.

2 responses to “Is Your Diet Soda Making You Gain Weight?”

  1. Marie says:

    The most compelling part of the non-intuitive assertion that non-nutritive sweeteners cause weight gain is the suggested mechanism. Eating or drinking something sweet, artificial or not, sends the same signal to our brain and kick off the metabolic response: insulin is released to deal with the perceived bolus of sugars, the insulin removes the “excess” blood sugar and stores it as fat, the now-lowered blood sugar makes one tired and hungry, and more calories are consumed to restore the blood sugar. Thus even though artificial sweeteners contain no/few calories, it is entirely credible to me that they could cause weight gain by storing fat and spurring appetite. Thus I think the healthiest recommendation would be to consume diet sodas, etc only with a meal or snack, not alone, just as you would a sugary dessert or drink.

    • Dana Notte says:

      Hi Marie – thank you for your comment.

      You are right that there has been some recent research to suggest that some artificial sweeteners may affect insulin levels and thus, could contribute to weight gain. The long-term implications of these findings are still unknown since this research is still relatively new. But, it does reinforce the point that avoiding excessive intake is probably wise.

      Consuming with food might help to mitigate the effects the sweeteners have on insulin levels. This is where I would encourage people to experiment with how their body feels when they consume diet soda with food vs. without food.

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About the Author

Dana Notte, MS, RD, CD

Dana has dedicated her career to helping individuals establish a balanced and healthy relationship with food. She has extensive training and experience in coaching for behavior change, mindful eating, and motivational interviewing. Dana has spent years leading group-based behavior change classes, developing and leading interactive workshops for worksite wellness programs, and providing nutrition counseling to individuals struggling with eating, weight, and chronic health conditions. Her practice style is client-centered, compassionate and empowering, with the goal of helping individuals develop the confidence to achieve their health and wellness goals. Dana is the Nutrition Lead at Green Mountain at Fox Run.

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