Do No-Calorie Sweeteners Make Us Fat?

Do No-Calorie Sweeteners Make Us Fat?

The Bitter Truth about Observational Studies
Are artificial sweeteners making us chubby? That’s what you might think if you skim the headlines or glance at study titles. Here’s the truth.

If you glance at the research on artificial sweeteners, or rather, the headlines about the research, you’ll think they’re best avoided.

“Just have regular sugar,” the normies will say. Too bad they don’t question what journalists tell them. Because, in truth, most regular journalists don’t know how to interpret scientific studies either.

When research shows that artificial sweeteners cause XYZ problems, you must ask. “How was the research done?” Is there an actual causation, or is it merely correlation?

So to cut to the chase, no, artificial sweeteners 12 and the soft drinks 6 they’re in do NOT cause weight gain. But read on to understand science a little better so you’re not duped in the future.

A Scary Study
Researchers recently found an association between several sweeteners and fat mass (1). Case closed, right? Not quite.

The weakness of observational studies is that they’re not able to show causation and are prone to many confounders. In this case, it’s quite clear that the associations found are due to a phenomenon known as “reverse causation.” In this case, those who are overweight or obese are more likely to consume non-nutritive sweeteners than sweeteners causing weight gain.

What did the researchers actually find?

They followed a group of adults over 25 years and gave them food questionnaires to gauge their intake of non-nutritive (artificial) sweeteners while also assessing their body weight and composition. Throughout the study period, total consumption of artificial sweeteners as well as consumption of aspartame, saccharin, and diet beverages, were positively associated with fat mass volumes, body mass index, body weight, and waist circumference.

However, interestingly, sucralose (Splenda 15) intake had no association with any of these variables.

How Do We Explain These Results?
If we take these results as the authors insist, total artificial sweetener intake can cause fat gain while sucralose does not.

That sounds great if you’re a big consumer of sucralose. Just keep in mind that when the media reports these findings, they’ll lump all sweeteners together and just tell you to consume the “real deal,” which is sugar-laden junk food and soft drinks.

Going back to the study, though, the most likely explanation for their findings is the association they neglected to consider between exercise habits, diet, and consumption of sweeteners. Granted, the researchers relied on self-reported food and physical activity questionnaires, which are notoriously unreliable. People forget, exaggerate, and often paint a very different picture of their own habits.

Nonetheless, when we evaluate the baseline characteristics of the study participants, we see that those consuming the highest amount of sweeteners were also the heaviest and had the greatest waist circumference. These were also the individuals who – if we believe the questionnaire’s accuracy – had the highest level of activity while also consuming the greatest amount of calories.

In the real world, these are likely the people who struggle with their weight. They try to out-exercise a bad diet and justify over-consuming calories – like eating brownies every night but justifying it because it was made with a sugar-free sweetener. Or the person who eats McDonald’s five times per day but has a Diet Coke each time to “balance it out.”

This is consistent with data from other studies where the majority (around 55%) of individuals regularly consuming diet soda were classified as obese (2).

Randomized Controlled Trials (RCTs)
How can we be so sure that this association is due to reverse causation rather than the sweeteners causing fat or weight gain?

In the hierarchy of scientific evidence, interventional studies consisting of randomized, placebo-controlled trials are the strongest. And unlike observational studies, these randomized controlled trials (RCTs) allow us to make conclusions about cause and effect.

When we look at what the RCTs find, it’s consistent that these sweeteners (including the “natural” sweetener stevia) either have no effect on variables such as fat mass or they actually decrease these variables (sucralose), especially when compared to those ingesting table sugar or sucrose (3-5).

This is also the case with meta-analyses of these RCTs, further strengthening the conclusions.

Take Home Points
Don’t give much credence to observational studies that find an association between artificial sweeteners and body fat.
The results from these observational studies are likely confounded by reverse causation.
Randomized, controlled trials consistently show either no effect on body weight and fat mass or, in some cases, a decrease, especially when substituted for sugar.