Most of you probably already know that diet soda isn’t good for you because, collectively, artificial sweeteners are associated with leukemia, brain tumors, breast cancer, bladder cancer, uterine and ovarian cancer, skin cancer, immune dysfunction, DNA damage, preterm delivery, and neurological problems.


But, in the moment, sometimes you just want a soda without all the extra calories. I get it.

Unfortunately, diet sodas aren’t even good for your waistline. Bizarrely enough, it turns out diet soda can still make you fat.

At first, this makes no sense — glucose (sugar) can get directly converted into triglycerides which get stored as fat, but artificial sweeteners cannot. It looks like the connection between your weight and artificial sweeteners has to do with your microbiome—the good probiotics in your gut.

Your Gut Flora and Your Weight

The Personalized Nutrition Project is a study which (among other things) correlated artificial sweetener consumption with individual gut flora populations. The study found that after even a week of artificial sweetener consumption, the bacterial configurations in the participants’ guts had changed, and they started to demonstrate signs of insulin resistance.

In fact, this study from the Journal of the American Geriatrics Society found that over a period of nine years, diet soda intake corresponded to three times the abdominal fat compared to non-diet soda drinkers.

(There’s another implication here too, and that is that probiotics are a good addition to a weight loss regime.)

Artificial Sweeteners and Leptin

Another potential reason for the connection of artificial sweeteners and weight gain may be that, while sugar has calories and therefore triggers the release of the ‘satiety’ hormone leptin (which tells your body you’re full and to stop eating), artificial sweeteners will stimulate the receptors in your tongue and your brain that say you’re eating something sweet, without the caloric payload.

This does two things:

  1. It trains you to crave sweeter treats. This is because artificial sweeteners are between 300-600 times sweeter than sugar.
  2. It lowers the body’s satiety response to sweetness. When sugar-like substances don’t sustain us, our bodies adapt, lowering the release of leptin. 

Bottom Line:

You’re not doing your weight a favor with the diet sodas… plus they’re laden with phosphoric acid, which acidifies your body and strips minerals from your bones, as well as artificial colors and flavors.

If you’re looking to wean off a bad habit, you might try health food alternative sodas such as Zevia (which still has artificial colors and chemicals in it, but isn’t as bad), or better yet, switch to fruit juice (which you can dilute with carbonated water if you’re craving the fizz), diluting it more and more over time to cut the excess sugar. Or just go straight to flavored carbonated water (I love the Trader Joe’s brand) or to iced tea.