Jan 29, 20203 min read

Does Diet Soda Break a Fast? [Simple Explanation]

Updated: Feb 3, 2021

Diet soda typically contains zero calories, so does that mean you can have it during your fast and still achieve your weight loss and wellness goals? Not necessarily. Today I'm breaking down the deets of diet soda and Intermittent Fasting!

But First... What IS Diet Soda?

Diet soda is the soda industry's answer to sugar. Instead of using the typical sweeteners such as sucrose (table sugar) or high fructose corn syrup - both of which contain calories - they opt for the no-calorie options. These sweeteners include acesulfame potassium and aspartame. You may even see more natural ingredients to this zero calorie approach with options like stevia and monk fruit.

But how can these diet or zero calorie soda's TASTE sweet if it doesn't contain sugar? It all comes down to the difference between taste and energy. Calorie is just a measurement of energy (more specifically kcal). Your body can derive energy from protein, carbohydrates or fat. These sweetener alternatives are not broken down in a similar fashion as the macronutrients protein, carbs and fat. Because of this, our body can't get energy from it. But what these sweeteners CAN do is provide a stimulus on your tongue that initiates the taste of sweetness. It's this bait-and-switch on your body concept that diet or zero calorie sodas are capitalizing on. Sweetness without the energy.

Can You Drink Diet Soda When Intermittent Fasting?

Technically speaking because most diet/zero calorie sodas do not contain protein or carbs that can cause an insulin response, it won't break your fast.

But here's the thing: although diet soda technically doesn't contain any calories and therefore should in theory not break your fast, it actually still could be working against your weight loss goals.

It all comes down to the fact that scientists are finding some people may secrete insulin (our fat storing hormone) to the sweet flavor even if it doesn't have any calories at all. Scientists have also found a concerning link between artificial sweeteners and issues with glucose intolerance and insulin resistance.(1) Considering one of the main objectives with Intermittent Fasting is to not spike your insulin so that you can help your body keep fat burning mechanisms up, this would totally work against your goals.

Not to mention scientists have also found that these artificial sweeteners may actually increase hunger (particularly sugar cravings) later in the day. (2)

This effect can include nearly all zero calorie sweeteners, including stevia. If you're curious on the science behind how zero calorie sweeteners may actually work against your weight loss goals, you can check out my complete breakdown with the video below.

However, it's important to note that scientists are finding that not everyone secretes insulin in response to non-nutritive (aka calorie-free) sweeteners. But if you're not losing weight with Intermittent Fasting and you've already fine tuned your meals to optimize fat burning, then you might want to take a look at your calorie-free sweetener intake. You might be surprised how much of an impact a "calorie-free" drink has on halting your weight loss progress.