The theory goes something like this…
When you consume artificial sweeteners, they ‘trick’ your body into releasing insulin since the sweet taste initiates what’s known as the cephalic insulin response, which is just a fancy way of saying the body gets ready to regulate blood sugar levels by releasing insulin, the hormone responsible for ushering glucose out of the bloodstream and into the cells.
But there’s a problem.
Unlike sugar, artificial sweeteners don’t bring any actual calories to the party. So, the body, expecting energy-rich glucose to arrive––which it isn’t going to receive––gets confused and pumps out insulin anyway.
And, well, now you’re screwed.
Everyone knows insulin is the ‘fat-storage’ hormone, so your body will start piling on the pounds (let’s ignore the fact these products are calorie-free, and the last time I checked, the body can’t create fat out of nothing, so what exactly is it storing?).
But it gets worse.
Because you never provided your body with any calories–in an act of biological revenge—it’ll increase cravings for sugar, and, like a mindless zombie, you’ll go searching for food, negating the calorie-free benefit of the diet drink. Womp, womp.
At least that’s what numbnuts on the internet want you to believe. In reality, artificial sweeteners, including aspartame, don’t seem to impact the cephalic response to any meaningful degree.
For instance, a 2017 systematic review investigated whether non-nutritive sweeteners influence acute glucose homeostasis in humans. As the authors write: 1
To date, studies using a pre-ingestive sweet taste stimulation design suggest that oral sweet taste activation from NNS [non-nutritive sweeteners] has limited effects on human glucose homeostasis.
*Note: “Pre-ingestive sweet taste stimulation design” refers to experiments where the sweet taste is experienced in the mouth, but the substance isn’t swallowed and digested.
But, the researchers also noted that:
Evidence in this area is mixed, where randomized controlled trials have reported decreased, no difference, or improved blood glucose control [from artificial sweeteners]. However, a recent meta-analysis of mostly observational studies concluded that the risk of developing type 2 diabetes increased with increasing NNS [non-nutritive sweeteners] intake.
And this presents the second problem with the research fuelling the “artificial sweeteners are going to fuck you” narrative: Observational studies can fall prey to reverse causation.
It’s possible that individuals who are already overweight opt for diet beverages in an attempt to manage their calorie consumption in order to lose weight. But did diet drinks contribute to their weight gain, or did these individuals turn to diet drinks after already being overweight?
Or, maybe people switch to diet beverages after they’re already at higher risk of certain disease states to try to cut down on their sugar intake? Observational research can’t control for every single factor.
Just to provide a particularly salient example of this: One study found higher intakes of diet drinks were associated with increased incidence of stroke only among the obese, with no association evident among those of normal BMI or overweight.
Furthermore, the participants in this study who had higher intakes of artificially sweetened beverages were, quoting the authors, “more likely to be obese, had lower levels of exercise, higher energy intake and lower diet quality as judged by HEI-2005, were more likely to be a current smoker, less likely to be a drinker, and were more likely to have a history of diabetes, myocardial infarction or cardiovascular disease.” 2
So again, is it just the artificial sweeteners causing these issues or is it all the other factors like a poor diet and a lack of exercise?
While observational research can give us insights into associations and trends, it can’t establish a direct cause-and-effect relationship due to its inherent limitations (like reverse causation). This is where randomised controlled trials (RCT) step in.
In an RCT, researchers might give half the participants an artificially sweetened drink and the other half a placebo, like water, and then see what happens.
Even better are systematic reviews and meta-analyses, where all of the research on a particular topic is gathered together and extensively analysed to see what effect artificial sweeteners have on the outcome being tested, such as whether or not drinking artificial sweeteners affects the body’s metabolic processes.
Thankfully, we do have these studies, and they tend to paint a very different picture than the one created by fear-mongering influencers on social media.
Take, for instance, a 2020 systematic review and meta-analysis, which included 34 human trials involving 452 participants, investigating the impact of artificial sweetener intake (including aspartame) on glucose and insulin levels after consumption. 3
To quote the researchers:
Intake of LES [low-energy sweeteners] had no statistically significant effects on the mean change differences in acute postprandial glucose or insulin responses compared with a control intervention.
The results didn’t change regardless of the type of artificial sweetener provided or how much of it was provided. In some of the studies they analysed, aspartame intake was as high as 500mg, or the equivalent of 6 cans of Coke Zero.
Moreover, a 2022 systematic review and meta-analysis included 17 randomised controlled trials (lasting between 3-52 weeks), totalling ~1700 adult participants (~77% were women) with overweight or obesity, investigated the association of artificial sweeteners with body weight and cardiometabolic risk factors.
The researchers found replacing sugary drinks with artificially sweetened drinks reduced body weight by ~1kg on average while also reducing the risk of cardiometabolic risk factors; benefits that were directionally similar to water. 4
AND––yes, I know, I’m exhausted too––a 2020 meta-analysis that focused solely on individuals with type 1 or type 2 diabetes arrived at similar conclusions: There was no “clinically relevant benefit or harm” to consuming artificial sweeteners. 5
I mean, I’m pretty sure if artificial sweeteners were screwing up people’s insulin levels, giving them to diabetics is probably the worse thing you could do. But I digress.
Even if we ignored everything just discussed and assumed artificial sweeteners did actually make people gain weight (e.g., through an increase in appetite), then we’d see that reflected in the research.
Yet, we see the opposite. When people swap sugary drinks (that contain calories) with zero-calorie drinks, they tend to lose weight.
For example, a 2021 meta-analysis found every 239 kcals of sugar replaced with artificial sweeteners resulted in a loss of ~1kg (~2 lbs). People also didn’t fully compensate for the reduced calorie intake by consuming more calories from elsewhere in the diet. 6
Also, if we continue with this line of reasoning—that artificial sweeteners make people gain weight—then, when compared with water, artificial sweeteners should result in worse outcomes, such as weight gain. But instead, replacing water with artificial sweeteners leads to neutral outcomes, i.e. people don’t gain or lose weight.
In other words, artificial sweeteners seem to work as intended: When they replace calories in the diet, people tend to lose a little bit of weight, and when they don’t, people don’t gain weight.
In sum
Artificial sweeteners can be a safe and effective way to reduce your energy intake and allow you to enjoy low- or zero-cal foods and drinks without additional calories. They also won’t spike your insulin and turn you into a big ball of human Jell-O. As long as you consume them sensibly–I mean, yeah, maybe don’t make Coke Zero your only source of fluid intake–there’s no need to give them up entirely.
Finally, I really don’t care if you consume artificial sweeteners; you can do whatever the fuck you want. But if you enjoy diet drinks and were worried you were committing nutritional seppuku, I hope this post alleviates those concerns.
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