As a teen and young adult, I drank a lot of full-sugar sodas—Mountain Dew, mostly. One day I decided that I would swap them all out for their diet equivalents, and the resulting loss of calories would mean I’d drop an easy five, maybe ten pounds by the end of the year. I stuck to my promise, and you know how many pounds I lost, changing nothing else about my diet? Zero.
I still don’t drink full-sugar sodas. (I am now, like my colleague Claire Lower, a member of the Diet Coke cult.) But I understand on a gut level why the World Health Organization issued a guideline arguing against using “non-sugar sweeteners,” such as aspartame, as magic bullets for weight loss or healthy eating.
If you want to see the scientific evidence they were working from, you can read up here (their meta-analysis of the health effects of sweeteners) and here (the guideline itself, 90 pages of evidence and recommendations).
By the way, I like that the World Health Organization is using the term “non-sugar sweeteners” (NSS) instead of “artificial sweeteners.” Stevia, for example, is “natural,” but it’s still in this category because it provides the sweetness of sugar without actually being sugar.
Why sweeteners don’t seem to help with weight loss or health
What I realized after my soda-switching experiment probably should have been obvious to all of us from the start: Our bodies are pretty good at making us hungry enough to eat and drink enough calories. Take calories away in one place, and we’ll just eat more of something else.
It’s hard to prove that’s what’s going on, but studies like the ones the World Health Organization cites pretty consistently show that people who consume a lot of non-sugar sweeteners aren’t thinner or healthier than those who don’t. In fact, some studies find the opposite, for what’s likely a reverse-causative reason. If you believe you need to lose weight, you’re more likely to order a diet soda. Therefore, people who routinely consume non-sugar sweeteners tend to be the same people who are categorized as overweight, or who have health problems they are trying to control with their diet.
The WHO’s pronouncement on non-sugar sweeteners is based on “the lack of evidence to suggest that NSS use is beneficial for body weight and other measures of body fatness over the long term,” not on any certainty that the sweeteners are actually bad for us. On the subject of potential long-term health effects, the WHO writes that “the evidence is ultimately inconclusive.”
You have to actually fix your diet if you want to eat healthier
The World Health Organization’s director for nutrition and food safety put it bluntly: “People should reduce the sweetness of the diet altogether” if they are trying to cut out sugar. If your diet isn’t as healthy as you’d like, swapping sugary foods and drinks for artificially-sweetened counterparts isn’t really changing your diet much at all.
(If you have diabetes, though, they say that non-sugar sweeteners may still have a place in your diet, since in that case, the point is to help you to eat less actual sugar. For the rest of us, the point is to improve our diet more generally.)
Instead, you should be eating more fruits, veggies, nuts, beans, and whole grains, they say. We have more ideas here on how to eat healthier without counting calories or obsessing over grams of sugar.
