Diet Soda On Keto: Are There Consequences?

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Reviewed by Dr. Maggie Herrmann, PT, DPT

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diet soda on keto
Diet sodas are keto-friendly but may negatively impact your health. Photo: Shutterstock

The keto diet is well known as a fat-loss diet with multiple health benefits. This carb-restricted diet leaves little room for sweets, thus some people turn to diet sodas for a quick, carb-free solution. However, the ingredients used to make these sodas sweet without using sugar can be detrimental to your health. 

Unlike coffee which can help you lose weight, diet soda can impede weight loss. In this article, we will discuss the risks of drinking diet soda and provide healthy alternatives to use while on the keto diet.  

Diet Soda On Keto

Soda products marketed as “diet” or “zero” have been formulated to remove sugars such as high fructose corn syrup and eliminate calories and carbs. However, to maintain the sweet taste, they must add artificial sweeteners.[1] These can have health consequences and should be avoided if possible.

The common additives to avoid include:

  • Aspartame.
  • Potassium benzoate. 
  • Phosphoric acid.
  • Acesulfame potassium.
  • Artificial flavors.

Can You Actually Drink Diet Soda On Keto?

diet soda on keto
Diet soda may be refreshing but have some negative effects. Photo: Shutterstock

Diet soda is technically allowed on the keto diet however it should be limited. The potential weight gain associated with diet soda impedes the weight loss benefit of the keto diet. Artificial sweeteners are associated with increased levels of insulin which can reduce the levels of ketones in the body, thus overdoing diet soda can impact the ketogenic diet.

The artificial sweeteners used in diet sodas can have a significant impact on the human body. Aspartame and sucralose, the artificial sweeteners in Diet Coke and Diet Pepsi, can alter the normal flora of the GI tract and allow harmful bacteria to populate the gut. Altered bacteria profiles can increase inflammation, triggering fat storage and weight gain.

Basics Of The Keto Diet You Should Know

The keto diet is designed to place the body into a state of ketosis leading to weight loss and many other health benefits. It is a high-fat diet in which 70% of the daily calories should come from healthy fat sources. It reduces carb intake to approximately 20-50 grams per day. For comparison, a medium sized banana contains 27 grams of carbs.

A ketogenic diet[2] has been associated with improved blood glucose control, weight loss, and improvements in cardiovascular health. The keto diet can reduce blood pressure, lower total cholesterol, lower LDL cholesterol, and lower triglycerides. 

These benefits are extremely beneficial in obese and type 2 diabetic individuals but can be very difficult to maintain for long periods. The extreme restriction on carbs is challenging and can result in carb cravings. Drinking diet soda is one way some people on the keto diet try to satisfy their sugar cravings.

Diet sodas often have zero calories with a net of zero carbs. Therefore, many people lean on Diet Coke, Diet Pepsi, and other diet drinks to fill the sugar gap of the keto diet. However, diet sodas often use artificial sweeteners which can have negative effects on your health.    

Carbs In Diet Soda

In regular sodas, high fructose corn syrup makes up the majority of sugars that provide the sweet taste. To reduce sugar, diet sodas use artificial sweeteners which do not count as sugar or carbs. These artificial sweeteners do have harmful properties that can be detrimental to your health. 

These artificial sweeteners include aspartame, potassium benzoate, phosphoric acid, acesulfame potassium, and artificial flavors. 

Although they do not alter blood sugar levels, they can increase insulin[3] levels by causing insulin resistance. Artificial sweeteners do not affect ketosis but can cause weight gain and stimulate inflammation which can have negative effects on heart health and increase cancer risks.  

Factors To Consider When Purchasing Diet Soda

Artificial Sweeteners

Companies use artificial sweeteners to mimic sugar without carbs. Given the keto diet is a strict low-carb diet, diet sodas appear to be a good choice. However, artificial sweeteners can be damaging to the body through the promotion of insulin resistance and inflammation. 

A healthy keto diet should avoid diet sodas like Diet Coke, Coke Zero, and other diet drinks using artificial sweeteners.  

Strange Colorings

Ever wonder what gives Diet Coke its caramel color or Diet Mountain Dew its yellow color? Well, it is the color additives used during the making of these products. Diet Coke uses a caramel coloring that is made by reacting corn sugars with ammonium and sulfite compounds, which also produces 4-MEI, a known carcinogen.[4] Diet Mountain Dew uses yellow number 5 dye, which has been linked to hyperactivity and migraines.

Diet sodas use coloring additives to increase their appeal, but these can have a big impact on your health and should be avoided.

Natural Sweeteners

By adding the word “natural” to the sweetener in the drink, many believe it is a healthier option. However, the natural sweetener, Stevia,[5] is also linked to insulin resistance and alterations in the GI tract’s normal flora. The use of natural or artificial sweeteners should not be considered a part of a healthy diet and should be avoided if possible. 

How Frequently Can I Have Diet Soda While On Keto?

It is recommended to drink diet soda as infrequently as possible, but a weekly Diet Coke will not significantly impact the keto diet. Early into the keto diet, diet soda can help one transition off regular sodas which can then be decreased over time. It is best to avoid diet soda while on a ketogenic diet, and probably all together as part of a healthy lifestyle.

Potential Side Effects Of Diet Soda

The negative effects of diet soda can negate the positive benefits of the keto diet. Diet sodas can also promote unhealthy eating habits and should be avoided when on ketogenic diets. There are more keto-friendly drinks that you can substitute for diet sodas to help prevent the following side effects.

Weight Gain

Does diet soda make you fat? Many people drink diet sodas due to the zero calories thinking it is healthier than regular soda, however researchers have shown this may not be the case.

People switching to diet soda were no more likely to lose weight than those who did not switch. The insulin resistance and subsequent increased insulin levels reduce the body’s use of fat stores and thus impair weight loss. 

A Negative Impact On The Gut Microbiome

Numerous studies have linked artificial and natural sweeteners with alterations in the bacteria populations in the gut. The increase in harmful bacteria can lead to increased inflammation which can lead to fat storage and weight gain. However, many of these studies[6] were conducted in animals and the long-term effect on gut flora in humans has yet to be fully explored.  

Increased Cravings

Acesulfame potassium is 200 times sweeter than sugar! Drinking beverages with sweeteners can alter the brain’s processing of sweet tastes and lead to cravings for sweet, carbohydrate-rich foods. This makes sticking to a keto diet much more difficult. 

Healthy Drinks That Can Replace Diet Soda On Keto  

To replace diet sodas, try some of these keto-friendly drinks. Not only are they compatible with the keto lifestyle, but some can also provide health benefits of their own. 

Coffee

A freshly brewed cup of black coffee has minimal calories and is carbohydrate-free. If needed, you can add some unsweetened milk as a creamer substitute or a limited amount of an artificial sweetener, but be sure to use these in moderation to keep the health benefits of coffee. 

The caffeine present in coffee can promote weight loss, reduce your body mass index, and promote fat loss.[7] Therefore, it can provide a boost to your diet.

Green Tea

Does green tea have caffeine? Yes, it is a carb-free alternative with a caffeine boost that can be used while on the keto diet. Additionally, it also is thought to have other health benefits.[8] Although the health benefits of green tea are still controversial, it is generally considered a healthy option. 

Water

Water is a natural, refreshing beverage alternative to diet soda. It can be spruced up using lemon juice or a slice of lemon, lime, cucumber, or strawberry for an even more refreshing drink. 

Carbonated Water

Sparkling water or carbonated water provides the fizz without the sweeteners for a low-carb drink. It can even be used to make your soda by adding natural flavors such as lemon juice or lime juice. Additionally, healthy sparkling water drinks can be purchased at stores that are also low carb and can satisfy the carbonation feeling of soda. An example of a brand of sparkling water is Lacroix.

Conclusion

Diet sodas should be avoided whether or not you are on a keto diet due to its negative effects on your health. Although they can be used on a keto diet, there are negative consequences associated with their use and should be limited as much as possible. Try to substitute a healthy keto-friendly alternative to maximize the diet’s potential and provide a refreshing beverage.

Frequently Asked Questions

Does diet soda affect ketosis?

Diet soda will not stop ketosis, but it can impact it. The ingredients in diet soda can cause an insulin-resistant state which results in higher insulin levels which can lower levels of ketones. Therefore, an occasional diet soda will not hurt you but consistent intake may impair ketosis.

What do artificial sweeteners do to the body?

Artificial sweeteners damage the body by promoting insulin resistance and inflammation.

Can I have diet soda on a keto diet?

It is recommended to limit your intake of diet soda while on a keto diet. Though it can be beneficial if weaning off regular soda, diet soda can still negatively impact your health.

What alternative drinks can I have instead of diet soda?

Water, carbonated water, green tea and coffee are all great options!

+ 8 sources

MIDSS adheres to strict procurement guidelines and relies on peer-reviewed studies, academic research institutes, and medical associations. We work mainly with peer-reviewed studies to ensure the accuracy of the information. We avoid the use of tertiary references. You can read about how we ensure the accuracy and timeliness of our content in our editorial process.

  1. Green, E. and Murphy, C. (2012). Altered processing of sweet taste in the brain of diet soda drinkers. Physiology & Behavior, [online] 107(4), pp.560–567. doi:https://doi.org/10.1016/j.physbeh.2012.05.006.
  2. McGaugh, E. and Barthel, B. (2022). A Review of Ketogenic Diet and Lifestyle. Missouri Medicine, [online] 119(1), p.84. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9312449/.
  3. Siew Ling Tey, Salleh, N.B., Christiani Jeyakumar Henry and Forde, C.G. (2016). Effects of aspartame-, monk fruit-, stevia- and sucrose-sweetened beverages on postprandial glucose, insulin and energy intake. International Journal of Obesity, [online] 41(3), pp.450–457. doi:https://doi.org/10.1038/ijo.2016.225.
  4. Tyler Jo Smith, Wolfson, J.A., Ding, J., Crupain, M.J., U. Srinivasa Rangan, Amir Sapkota, Bleich, S.N. and Nachman, K.E. (2015). Caramel Color in Soft Drinks and Exposure to 4-Methylimidazole: A Quantitative Risk Assessment. PLOS ONE, [online] 10(2), pp.e0118138–e0118138. doi:https://doi.org/10.1371/journal.pone.0118138.
  5. Ajami (2020). Effects of stevia on glycemic and lipid profile of type 2 diabetic patients: A randomized controlled trial. Avicenna journal of phytomedicine, [online] 10(2). Available at: https://pubmed.ncbi.nlm.nih.gov/32257884/.
  6. Francisco Javier Ruiz-Ojeda, Plaza-Diaz, J., María José Sáez-Lara and Gil, A. (2019). Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials. Advances in Nutrition, [online] 10, pp.S31–S48. doi:https://doi.org/10.1093/advances/nmy037.
  7. Tabrizi, R., Parvane Saneei, Lankarani, K.B. and Zatollah Asemi (2018). The effects of caffeine intake on weight loss: a systematic review and dos-response meta-analysis of… [online] ResearchGate. Available at: https://www.researchgate.net/publication/328378300_The_effects_of_caffeine_intake_on_weight_loss_a_systematic_review_and_dos-response_meta-analysis_of_randomized_controlled_trials.
  8. NCCIH. (2020). Green Tea. [online] Available at: https://www.nccih.nih.gov/health/green-tea.

ABOUT THE AUTHOR

Dr. Shaun Kink is a orthopedic surgeon and pharmacist by training with extensive experience in medical writing and research. He enjoys writing about all topics in healthcare, especially orthopedic and pharmaceutical topics.

ABOUT MEDICAL REVIEWER

Maggie is a Doctor of Physical Therapy with a passion for improving society's health and wellness. As a PT, she treats anything from pelvic floor and TMJ to shoulder, knee and hip conditions in the out-patient setting. She enjoys writing and reviewing healthcare content to provide information in an engaging and informative format.
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