Last Updated on November 9, 2023 by Fasting Planet
You started your latest fast a couple of hours ago, and you sure are thirsty. It’s very important to stay hydrated on a fast, so you should definitely have something to drink. What if your beverage of choice is diet soda? Is that appropriate to drink on a fast?
No, you should not drink diet soda when fasting. It may not contain many calories, but diet soda is loaded with ingredients like sucralose and aspartame that may cause you to gain weight rather than lose it.
In this article, we will explore diet soda in much more detail, including what’s in it and why you want to avoid the fizzy beverage on your fasts. We’ll even provide some better alternatives to sip when your thirst strikes.
Let’s begin.
What Is Diet Soda?
This may seem like an obvious question, but stop and think for a moment. Each time you open that can or bottle of diet soda, do you know what you’re consuming? Allow us to tell you.
Diet soda goes by several names, such as light drinks, zero-calorie drinks, and sugar-free sodas.
The main selling point of diet soda is that it contains few if any calories. Just look at the nutrition facts for a 12-ounce can of Diet Coke. It’s completely calorie-free. It’s also missing carbohydrates, total sugars, total fat, and cholesterol.
What else is this soda lacking? Potassium, iron, calcium, vitamin D, and protein. The drink also has 40 milligrams of sodium, or two percent of your recommended allowance for the day.
The diet soda formula is exceedingly simple, as it includes these ingredients.
Caffeine
Don’t be fooled. Diet soda is still soda, so it does contain caffeine. How much caffeine you ingest varies depending on the brand of diet soda you like, but it’s between 34 and 46 milligrams per can. An average serving of cola contains about 39 milligrams of caffeine, so you’re not necessarily getting less caffeine by going the diet route.
Minerals and Vitamins
Yes, you read that right. Despite that it’s soda, diet drinks may have some minerals and vitamins packed into those bottles and cans. The goal of this is to make diet soda seem healthier, even though it isn’t.
This 2016 article in ScienceDirect mentions herbal extracts may get added to your drink, as may the antioxidant ascorbic acid, also known as vitamin C. This isn’t so much for health reasons as to enhance the flavor and color stability of the diet soda.
Preservatives
Potassium benzoate and other preservatives get loaded into diet and non-diet sodas alike so they don’t expire the moment they reach the grocery store shelves.
Artificial Flavors
The same ScienceDirect article notes that some flavors used in diet soda are cola, herbs, berries, fruits, and natural juices. Other, more artificial flavors are included in the beverage during manufacturing as well.
Colors
You want your diet soda to look like…well, soda. With caramels, anthocyanins, and carotenoids, your diet drink will take on that distinct dark brown hue.
Acids
Phosphoric, malic, and citric acids are a mainstay in sodas, as without them, your drink wouldn’t be so tart. It’s a shame that sipping these acids often can begin to wear away at the enamel that covers your teeth. Once it’s gone, tooth enamel doesn’t come back.
Sweeteners
Diet soda tastes different compared to its regular soda counterparts, and that’s due to the sweeteners within. These include sucralose, acesulfame-K, saccharin, cyclamate, and/or aspartame.
These are all artificial sweeteners that make the diet soda sugary enough to be appealing, but not enough that it has as much sugar as a regular soda.
Carbonated Water
Water combined with carbon dioxide produces that bubbliness that makes soda so appealing.
Why Can’t You Drink Diet Soda While Fasting?
Okay, so you now understand what’s in your diet soda. Given that most diet drinks have no calories, why shouldn’t you consume them to get through your fast?
There are two primary reasons, so let’s discuss these both more now.
Calories
Wait, didn’t we just establish that diet soda has no calories? Not exactly. As we’ve said, not all diet sodas have calories, but some do. This may amount to something like five calories a can, which is low.
However, as we’ve written about on this blog before, for some types of fasts, if you consume any calories, you’ve effectively broken the fast. A beverage you drink outside of water has to have zero calories. That is possible, by the way, and we’ll recommend some options later in this article.
There’s also the matter that even though your diet soda may say it has zero calories, that doesn’t necessarily mean it does.
What do we mean by that? This snarky article from the American Council on Science and Health or ACSH from 2018 explains it. One primary artificial sweetener in diet drinks, aspartame, is to blame for the extra caloric load.
The aspartame molecule comprises aspartic acid. This attaches to a phenylalanine molecule through amide bonding. That phenylalanine molecule is connected to a methanol molecule, this time by ester bonding.
Phenylalanine and aspartic acid are considered amino acids that make protein. For example, if you have eight amino acids connected by seven amide bonds and the bonds get digested, you’re left with more amino acids. Peptidase, a type of enzyme, will digest the proteins as well as aspartame.
If aspartame is technically a protein, then it carries the same caloric load as a protein, the ACSH article states. That means that for each gram of aspartame in your diet soda, you’re consuming four calories.
Granted, this isn’t much. If you drink a single can of Diet Coke that’s 12 ounces, it contains 125 milligrams of aspartame. ASCH mentions that not all that aspartame has aspartylphenylalanine proteins, only 113 milligrams. This leaves you with 0.028 calories per can.
So yes, you’d still break the fast by drinking “zero-calorie” diet soda.
Artificial Sweeteners
Besides deceptively adding calories to a soda that’s supposed to have none, artificial sweeteners do a far more devious job.
If you’re fasting, there’s surely a reason behind it. Perhaps you want to reset your system or boost your immunity. You may have to fast for a medical test or religious observance. Many people fast for weight loss.
Whether you fast for a prolonged period or intermittently, you achieve weight loss the same way. It’s a two-pronged approach, really. For one, by consuming fewer calories than you burn, the pounds come off.
You also burn fat if your fast is long enough. First, you have to get through your body’s supply of glucose, which comes from the foods we eat. When time does away with all that leftover glucose, your body uses fat as the main energy source. This also helps you look better and lighter.
Diet soda, with its few calories, seems like it wouldn’t interrupt your weight loss goal, or at least, it did before you read this article. Now you’re not so sure.
You’d be right to have your doubts. Mounting evidence points towards a link between drinking diet soda and gaining weight, not losing it.
One of these, a 2010 study from the British Journal of Nutrition, found that drinking “calorie-free” beverages like diet sodas can cause you to become hungrier for more calories, not to mention more sugar. Further research will be needed to solidify this link, but it is something to think about.
Also, this 2017 ScienceDirect report and a slew of other studies have reached a similar conclusion. The data says that your hunger hormones are activated when you drink diet soda. This makes you hungry, so you seek out more foods to fill your stomach.
In an International Journal of Clinical Practice study, also from 2017, the researchers found that when you drink diet soda to excess, you may be more likely to develop metabolic syndrome and obesity. This again comes back to the artificial sweeteners.
This Inc. article also highlights a few reasons the sweeteners in diet soda can be so dangerous for our waistline. For one, the article mentions how if we make a smart choice like choosing diet soda over regular soda, some people might think that entitles them to eat more. This either balances out your caloric load or even increases it more than if you had just drunk the regular soda.
Inc. also says that artificial sweeteners tend to taste more saccharine compared to normal ol’ sugar. You might think that regular soda has a sweeter taste than the diet variety, but it’s actually the other way around. The paltry few calories but lots of sweetness affects metabolic processes, which enhances sugar cravings. This again has you spending more time in the fridge or pantry seeking out sugar.
Another big reason diet soda may cause weight gain that Inc. mentions is the boost in insulin production. The sugary flavor in the artificial sweeteners tells your pancreas to make insulin. However, the artificial sweetener is sugar in taste alone, not composition. This too can affect our metabolic processes, as the pancreas gets confused when we taste something sweet but no sugar enters our system.
That could tie into the increased rate of metabolic syndrome in diet soda drinkers that we mentioned above. This syndrome can increase your blood sugar, blood pressure, and make you overweight, Inc. mentions.
There are arguments against diet soda being a culprit in weight gain as well. In 2008, the journal Obesity (Silver Spring) suggested that most diet soda drinkers already have poor eating habits. Thus, it’d be these dietary habits that would cause their weight gain, not the soda itself.
Some studies even indicate that diet soda could help you meet weight loss goals, such as this 2016 report in Obesity (Silver Spring) (different link than above). It involved a group of participants who drank diet soda.
Each of the participants was overweight. Every day over the course of a year, they consumed either 24 ounces of water or diet soda. The group drinking water lost 5.5 pounds. Those who consumed diet soda dropped 13.7 pounds.
That doesn’t make much sense considering that water has no calories, guaranteed, and diet soda can be caloric. In some instances, artificial sweetener companies may have a pull over studies and their results, which can skew their accuracy and muddy up the waters of whether diet soda is a smart drink choice.
Can You Drink Diet Soda to Prepare for a Fast? What about Post-Fast?
As you gear up for a fast, what you consume matters. This is something we’ve talked about extensively on this blog, as your food and beverage choices can be the difference between a successful or a disastrous fasting experience.
If you’re planning to do a liquid-based fast such as a water fast, it’s better to wind down and drink mostly liquids in the day or two before the fast begins. In the past, we’ve recommended smoothies as well as natural fruit and vegetable juices.
Does diet soda have any place in your pre-fasting diet regimen? We’d say no. It’s not so much about the calories here, as you’re still allowed to consume calories since your fast hasn’t started yet.
Instead, it’s more about aspartame and the other artificial sweeteners in diet soda and how they mess with your body. Remember, these sweeteners can disrupt metabolic processes and confuse your brain and pancreas. Your body doesn’t understand why, when it tastes sugar, there is no sugar present.
Besides all the unwanted changes that artificial sweeteners can induce, such as increased insulin, you also have to worry about sugar cravings. If you drink a diet soda before your fast and it leaves you eager for sugar, the fasting period ahead is going to be a very difficult one. You won’t necessarily be hungry for food, but sugar.
If those cravings persist for the duration of your fast, then the first thing you’ll consume when you can eat again is sugar. Depending on the quantities and how long your cravings last, you could derail any weight loss progress you may have made on the fast.
Okay, so diet soda is a no-no ahead of your fast. What about when you’re finished? Can you pop open a crisp, cold can of diet soda to reward yourself for a job well done?
Well, you could, but again, we’d seriously caution you against it. You’re at risk of once again triggering those sugar cravings. Combining your cravings with your hunger from not eating for a day or several and you can make really poor dietary decisions as soon as you can eat.
Besides the risk of gaining back all your weight, you also could develop refeeding syndrome. This is something that’s come up on this blog before, but we’ll recap it here.
Refeeding syndrome is a metabolic condition that most frequently affects those who fast or are malnourished. By consuming calories in large quantities in either liquid or solid form, your phosphorus, magnesium, and potassium blood concentrations decrease while glycogen production increases.
This is just as dangerous as it sounds. The most serious symptoms of refeeding syndrome are heart failure and seizures. It can be deadly, so skip the diet soda immediately post-fast too.
What Can You Drink on a Fast?
Diet soda had at one time been promoted as a smart choice for athletes and diabetics to drink. That’s despite the evidence that your blood sugar can spike if you’re a regular diet soda drinker. Even still, we still wouldn’t advise you to drink diet soda on a fast for the reasons we’ve described.
That brings us to another question. If you have to pass on the diet soda while fasting, what other beverage options do you have?
Here are some zero-calorie and low-calorie drinks that won’t break your fast or put you at risk of weight gain while fasting.
Water
It’s impossible to go wrong with water. We ourselves are made of water, at least 60 percent of our bodies. We also need the beverage to survive. You’ll only last about three days without water, where with food, it can be upwards of 21 days.
Water has zero calories, and yes, that truly means zero calories. You don’t have to worry about any hidden calories like diet soda. Also, water has a blank nutritional profile: you’re not ingesting artificial sweeteners, sodium, carbs, or fats.
Drink it often to induce a feeling of fullness on your fast. Even if you’re not water fasting, water is a great beverage to keep you hydrated any day, anytime.
Bone Broth
We just wrote a great article about bone broth and how you can consume it on a fast. As a reminder, bone broth or stock can come from animal bones, meat, seafood, vegetables, water, and wine. The healthiest bone broths for fasting are those you make at home so you can control ingredients and limit preservatives.
If you do that, then you can sip on bone broth often throughout your fast without adding many calories to your diet.
Apple Cider Vinegar
If you remember our post on beverages that break a fast, we talked about a curious but safe beverage choice for fasters: apple cider vinegar. We said then that it’s an acquired taste, and that’s still very much the case.
Each time you gulp down apple cider vinegar though, you may experience such benefits as an increase in insulin sensitivity, decreased blood sugar, and improved heart health. There’s even evidence that apple cider vinegar can help you lose weight.
Conclusion
Diet soda may seem relatively harmless because it’s a zero-calorie drink. As it turns out, even the no-calorie sodas contain trace amounts of calories. More damning are all the artificial sweeteners. Many studies have concluded that aspartame and other faux sugars can contribute to weight gain.
The next time you feel thirsty on a fast, stick with apple cider vinegar, water, or homemade bone broth.