Nutrition Do Diet Sodas Boost or Sabotage Fat Loss?

diet sodas - do they sabotage fat loss?

So you’ve decided to lose weight? Then you’ll need to reduce your caloric intake, starting with refined sugars — a daunting prospect for those of us with a sweet tooth, but nowadays we’ve got an ally: sweeteners.

Every day, people are swapping out sugar for no- or low-calorie sweeteners. The most popular sugar-free product of them all: diet sodas. Fizzy, just as sweet, and completely guilt-free … or are they? In recent years, you’ve probably read articles warning that diet sodas, far from being on your side, conspire to sabotage your dieting efforts. Even worse: They’ve been accused of sabotaging your very health, with effects ranging from headaches to autism to cancer.

And so, you’ve probably asked yourself this question: Could sweeteners actually be worse than sugar? And first of all …

What are sweeteners?

Sweeteners is the popular name for low- or no-calorie sugar substitutes, be they natural (e.g., stevia), synthetic (e.g., aspartame, sucralose), or chemically altered (e.g., sugar alcohols).

A common misconception is that natural is always better than artificial, but natural compounds are complex and thus more likely to have “hidden effects” — some positive, some not. Stevia is more likely to cause allergic reactions or interact with some drugs than sucralose, for instance, but it might also hinder some cancers.

Synthetic sweeteners are simple. Each is a unique molecule, and though a molecule will also have effects both positive and negative, it’s easier to study than a compound. Like natural sweeteners, however, synthetic sweeteners do not constitute a uniform category; some are structurally similar to sugar, but not all. Sucralose is. Aspartame, on the other hand, is made of amino acids.

Sweeteners can be artificial without being synthetic. Sugar alcohols are chemically altered plant carbohydrates. Rather than in diet sodas, they’re usually found in sugar-free candies and other solid foods. They’re low in calories, not calorie-free, and in sufficient amounts can elevate your blood glucose (diabetics beware).

What are the downsides to drinking diet sodas?

There can be two downsides to drinking diet soda. One is chemical; the other, psychological. The psychological effect is twofold: First, drinking sweet beverages makes everything else taste less sweet, with the result that you end eating sweeter and sweeter foods. Second, people who switch to diet sodas assume they’re cutting calories from their diet, whereas in fact they often start eating more to compensate.

This second effect is partly psychological (I drink diet sodas now, so I can eat whatever I want) and partly not. Studies that gave sodas with or without sugar to different people noted that the participants who (unknowingly) drank the sugar-free sodas were liable to eat more over the rest of the day.

The culprit is probably insulin — or rather, its lack. In non-diabetics, insulin suppresses appetite (indeed, insulin inhalants have been studied for this purpose). Sweeteners cause you to release some insulin, but less than sugar does, so the latter is better at decreasing appetite.

Other chemical downsides to drinking diet sodas depend on their ingredients, and notably on the kind of sweeteners they contain. As we’ve seen, sweeteners do not constitute a uniform category, and so cannot be judged wholesale.

Saccharin (Sweet’N Low) is considered safe in small doses but potentially hazardous in high doses. This is why you can still find it small packets in diners but no longer in products sold in supermarkets. For this latter purpose, it has been replaced with other sweeteners, notably stevia and aspartame.

A common misconception, as we’ve seen, is that natural is always better than artificial. No surprise, then, if aspartame, being both widespread and synthetic, has been under fire from scientists and bloggers alike.

The science on aspartame, however, is mostly solid. Yes, this sweetener can promote cancer if given to rats in astoundingly high doses — but unless you’re going to guzzle pound after pound of pure aspartame to prove a point, you’re safe. One old study associated lifetime ingestion of aspartame with an increase in cancer in rats, but it couldn’t be replicated. Today, most rodent evidence, as well at what human evidence is available, shows no link between aspartame and cancer. The worst we can currently say about aspartame is that it might cause headaches in some people.

Why does the media keep demonizing diet sodas?

As is often the case, it’s a mix of disinformation and misinformation.

Disinformation propagates when people, well, lie. Some people will lie about one product to sell you another. Some people will lie because a shocking lie sells more papers (or generates more clicks) than a tame truth. Some people will lie because they like to trick and scare people — or to prove a point, as did John Bohannon.

Misinformation propagates when people parrot “facts” they haven’t doubled-checked. After all, reading the science is hard and takes time, which is why a 2012 survey assessing the quality of the evidence for dietary advice given in UK national newspapers found that between 69% and 72% of health claims were based on deficient or insufficient evidence.

Overworked journalists with looming deadlines frequently rely on study press releases, which often fail to accurately summarize the studies’ findings; so yes, even the traditional press can be fooled — and thus fool you — as John Bohannon proved when his chocolate diet hoax made the rounds.

And the more something is repeated, the more “true” it becomes, to the point that facts stop to matter. When companies decide to replace aspartame in their diet sodas by another sweetener, their decision isn’t based on what science says about aspartame, but on what their customers think about it.

… or what they think their customer think about it, since when Pepsi replaced aspartame by a mix of sucralose (Splenda) and acesulfame potassium, its sales suffered as people complained about the taste.

Final verdict

Sweeteners are low- or no-calorie sugar substitutes, either synthetic or derived from natural sources. There are many different kinds, which are continuously researched and compared for their safety and efficacy, and the ones in diet sodas today do not have known side effects at dosages seen in real life.

So why are diet sodas demonized? Part of it is disinformation (by companies, to sell you a competing product; by publications, to grab your attention), part of it misinformation (such as when a study feeds rats a diet of aspartame, and well-intentioned people apply the results to humans consuming one or two or even a dozen cans of sodas a day).

No, diet sodas won’t hurt you. They don’t inherently promote weight loss, either, but if they make your life easier, no need to shun them — the worst that may happen is an upset tummy and some gas from the carbonation.


What do you think?