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rants & raves

my thoughts on nutrition, food, research and everything in between


Diet sodas: helpful or harmful for weight management??

Alison Boden

This is a controversial topic in the nutrition research arena.

Enter diet soda. No calories, no sugar. A popular choice among those trying to quit regular soda (we all know the higher rates of obesity and diabetes with regular soda consumption). Seems harmless right? You should easily lose weight if you switch over from regular and keep drinking the low cal stuff for ever and ever and ever? The holy grail of #haveyourcake and eat it too?


Maybe not.

Let's put down (for now) the potential links we've seen between diet soda and cancer, or diet soda intake and stroke risk. Or diet soda and metabolic syndrome. Or diabetes. No let's not talk about these and just look at the weight connection.

Here's the oversimplified breakdown:

Short duration, clinical trials (like this shiny new one funded by the American Beverage Association) often show favorable results on weight management when subjects drink diet sodas. Typically they compare drinking regular soda to diet soda and measure effects on weight. A lot will lose more weight (or gain less weight) if assigned to the diet soda intervention group.

So case closed, right? Diet soda makes you lose weight?

Not so fast. So these are usually short duration studies. We have research subjects make a temporary change in their behaviors and habits, and then measure the results. We can't always trust that these short term results in a very controlled setting are applicable to "real life." So we have to look at other studies, that follow people for longer periods of time in the real world. It's with these type of studies that we see the opposite effects of the clinical trials (like this one, showing that those with 2-a-day diet coke habits over 10 years time had an average waist size increase by 5 fold compared to water drinkers. 5!).

Ok that's a lot of data. Here's my general take on things:

Artificial sweeteners (think diet cokes, or splenda in your coffee) are sweeter than sugar. Like, a lot sweeter. Sometimes 600x sweeter. While I can't really wrap my brain around that bit of data, I do know that those who eat/ drink the most artificial sweeteners tend to have more of a sweet tooth. Makes sense right? You're eating or drinking something that's SO MUCH sweeter than anything you could ever find in nature. So by drinking your coffee with 2 splenda, you're saving 30 calories by not using 2 teaspoons of regular sugar, but you're exposing your taste buds to something crazy sweet. That ups your threshold for sweetness, and you basically train your palate to expect uber sweet stuff all the time. Bitter tastes become more bitter, and although you saved those 30 calories this morning, and 150 calories this afternoon with your diet coke, you're much more likely to eat some dessert at the end of the day. I see this all the time with my patients and clients.

So best case scenario: diet sodas don't necessarily do anything bad for you, but make you more likely to eat sugar in other forms, thus contributing to weight gain.

Worse case scenario: The above, plus there's some real creepy stuff in fake sugar that independently may also cause diseases like cancer and diabetes.

Worth the risk? Get off the sauce, man.