Is Diet Coke Bad For You? What About Artificial Sweeteners?

diet coke

There’s one question we get asked probably more than any other:

“Is Diet Coke bad for you?”

I get why this has caused so much confusion and debate. We all know sugar is worse for us than Darth Vader, so Diet Coke, with NO sugar, has to be better for us.

However, we’ve also been told Diet Coke is packed full of chemicals like aspartame that do all sorts of awful stuff…which would then make Diet Coke worse than Jar Jar Binks, right?

What’s the truth? Does the lack of calories in Diet Coke help us? Do the chemicals and other additives make it a horrible beverage choice

The answer is…maybe, but it’s not that simple.

Regardless of whether or not you drink diet coke once a month or you drink a twelve pack every day, it pales in comparison to the impact your diet will have on your weight.

For a lot of rebels who come to Nerd Fitness, the question on whether or not to drink Diet Coke instead of regular sode (or even water) is part of a bigger problem they are spending time on – “What should I be eating and drinking? How much? And when?”

In other words, this is a small piece of a much larger puzzle: “I want to lose weight, I’m trying to be healthier by drinking Diet Coke, but I need the caffeine and I work in a high stress job. HELP ME, STEVE!”

I can hear you yelling at your computer or phone right now.

Today we’re gonna get into the science of Diet Coke and aspartame, but I’d be remiss if I didn’t mention a program that is helping busy people like you who struggle with sugar cravings, buckets of caffeine, and are also trying to lose weight! All of these things are connected, and it’s why we started our 1-on-1 Online Private Coaching program: no judgment, no guesswork – just guidance from a NF coach who will help you navigate a busy lifestyle with nutritional instruction and handcrafted workout routines.

Schedule a free call with our team so we can get to know you and see if we’re a good match for each other! Just click on the image below for more details:

Okay, let’s get into the science of Diet Coke!

Diet Coke doesn’t make you fat…

Coke case

Diet Coke does not make you fat…directly.

As pointed out in this exhaustively extensive article from my friends over at, Diet Coke and other zero-calorie beverages do not inherently cause weight gain:

“There are no studies that indicate any long-term health risks from drinking diet soda. Diet soda (defined as calorie-free carbonated beverages sweetened with aspartame, sucralose, acesulfame-potassium, or other non-caloric or minimally caloric sweeteners) is not harmful to health, well-being, or body composition.” 

We’ve already covered in a previous article “Is a calorie a calorie” that consuming fewer calories is the first step in a process to losing weight.

Consuming a Diet Coke compared to drinking a regular Coke means you are consuming significantly fewer calories per day. If you consume multiple Cokes per day, switching to Diet Coke could result in thousands of calories less consumed each week.

There’s been quite a big discussion out there about the effect of artificial sweeteners on how our bodies react, specifically with insulin resistance and things of that nature.

However, this study suggests that artificial sweeteners don’t play a significant role in the secretion of insulin, compared to the consumption of regular sugar.

So what gives!? What’s with all of those studies and things we’ve heard about where people who GAIN weight while consuming diet soda? Although Diet Coke isn’t directly responsible for weight gain, it’s no innocent bystander either!

…But it’s No Saint either.

coke mirror

Diet Coke and diet sodas are kind of like the getaway driver in a bank robbery. Sure, they didn’t technically rob the bank, but they are guilty by association.

The reason we’ve heard diet soda can cause weight gain can be explained with this study:

“Although overweight and obese adults who drink diet soda eat a comparable amount of total calories as heavier adults who drink sugary beverages, they consume significantly more calories from solid food at both meals and snacks,” lead study author Sara Bleich said in a press release. “Diet soda is not making people fat,” Dr. Chris Ochner, who researches obesity prevention and treatment, said to CBS News. “Eating too many calories is making too many people fat.”

Diet soda might not CAUSE weight gain, but it is correlated with being overweight and unhealthy – people who consume diet soda often assume they are making healthier choices about their beverage (which they are), but as a result are consuming MORE food calories than they expected.

This is why you often see three Big Macs and a large fry accompanied by a large diet coke. Or why people get upset when they gain weight on a gluten-free diet, even though their diet is composed of gluten-free cookies, cake, muffins, pancakes, and pasta. These folks are missing the point!

Although we know correlation does not prove causation, it appears diet soda is causing OTHER issues beyond simply increasing our waistlines. Specifically, it can cause us to underestimate how much food we are eating, or lull us into a false sense of healthy security when it comes to consumption.

And from a behavioral and habits perspective, it keeps us needing something “sweet” in our lives.

There’s other thing I’d like to mention about diet sodas, as this is something that has become SO mainstream it’s almost taken as a fact….

what about aspartame?

coke back

If I told you “aspartame causes headaches and cancer,” you’ll likely respond in one of two ways:

  • What’s aspartame?
  • Of course it does.

If you don’t know what aspartame is, it’s an ingredient in Diet Coke that replaces sugar – it’s 200 times sweeter than sucrose so only a small amount of it is used. However, it’s been widely regarded by the public that aspartame is a cancer-causing agent and should be avoided at all costs.

What’s the truth here?

It turns out, aspartame’s association with cancer is much cloudier than you’ve heard.

For starters, there may be some truth to the rumor that aspartame can cause headaches for some people, though not nearly enough studies have been completed to prove this definitively and a placebo effect might be in place due to aspartame already being seen as the villain.

As far as aspartame causing cancer, this has also never been definitively proven.

Back in 1996, a study suggested there might be a link between the increased chance of developing a brain tumor and the consumption of aspartame, but this was proven false.

Also, a study in 2005 saw an increased risk of cancer development in rats who were fed aspartame. However, the results were inconsistent, and these rats were fed an equivalent of hundreds of cans of diet soda per day.

Finally, “NCI examined human data from the NIH-AARP Diet and Health Study of over half a million retirees. Increasing consumption of aspartame-containing beverages was not associated with the development of lymphoma, leukemia, or brain cancer.”

Note: this is not an endorsement of aspartame, but simply an attempt to shed some light on a controversial subject. If you are concerned about aspartame consumption, avoid it.

We’re confident that aspartame becomes a non-issue anyway. Why?

what does Nerd fitness say?


Our advice can be simple and straightforward: Don’t drink soda! It’s terrible for you. Sugary beverages (soda, fruit juices, etc.) can lead to weight gain, diabetes, metabolic syndrome, and a host of other issues. If you drink soda now, try drinking less. A twelve pack of Mountain Dew every day is NOT a good habit for you.

But you don’t need to change overnight. Try 11 tomorrow.

However, as we know drinking a lot of alcohol isn’t good for you either, be smart about how much and what you drink to make sure you don’t derail your healthy lifestyle. If you are jonesing for a soda, choosing a diet soda over a regular soda is a good start. Life is short, and if a single Diet Coke is going to make your day a bit happier and stave off a worse decision, go for it.

However, we don’t recommend you just replace soda with diet soda, and not change anything else (and expect to see drastic changes).

I want you to think about WHY you are consuming so much soda, be it regular or diet:

If you are consuming soda for the caffeine content, switching to diet soda is a tool to get started. Read up on our thoughts on caffeine here, but you’d be much better off with black coffee and green tea.

If you are consuming soda because you’re addicted to sugar, then we have a much bigger habit problem to deal with….but it can be dealt with.

We’re interested in permanent, antifragile solutions, and Diet Coke is a temporary hack to a much deeper-rooted problem: your source code when it comes to sugar or caffeine addiction. By fixing your code at the source, you can start to wean yourself off of sugary beverages and artificial temporary solutions.

Not sure the best way to change your diet, or tired of losing weight only to gain it back? You need a better blueprint strategy to follow! In addition to our Online Coaching program where you get personalized guidance and instruction, we have a 10-Level Nerd Fitness Diet treats the process like a game, and allows you to pick the level you’re comfortable with, and only has you leveling up after you complete a 2-week challenge.

Grab our Nerd Fitness Diet strategy guide when you sign up in the box below and join the Rebellion. Get healthy the right way. Get healthy permanently.

Long story short: we want to create long-term healthy systems that have us eating healthy foods and avoiding liquid calories. This is about building good strong habits, and keeping ourselves making healthy happy eating choices.

Although swapping out soda for diet soda is a solid step in the right direction, the true solution is retraining and rewiring our body so we don’t need to chase that sugar fix; we can slay our addiction to sugar entirely.

tl;dr – Soda is legitimately terrible for you. Sugar is Darth Vader. Diet soda can be a stepping stone between sugar addiction, the need for sugary beverages, and FREEEEEDOM:

What are your experiences with diet soda? Did you use them as a tool to help you lose weight? Or did you struggle with weight loss until finally dropping diet soda out of your daily consumption as well?

Leave it in the comments!


PS – Phew, if you made it this far, I want to share two ways you can get more in-depth training, advice, and help making fitness a priority. As we mentioned, our first is our 1-on-1 Online Coaching ProgramNo more shame, no more hiding what you eat, no more guesswork – you’ll get expert guidance and accountability from a professional on Team Nerd Fitness who gets to know you better than you know yourself!

Sound good? Head over to our Coaching page and schedule a free consultation to see if it’s right for you!

PPS: 40,000+ rebels have joined us in the Nerd Fitness Academy! If you’re interested in strength training and want more specific workouts to follow, nutritional advice and meal plans to pick from, a boss battle system, character leveling system, and a supportive community, check it out.  We’d love to help you level up with us.  See you inside!


photo pin: Sarah Korf: nutritional information, Ryan Hyde: Water, Mike Mozart: Diet Coke, Laura Lewis: mirror, Mike Mozart: Diet Coke

Get The Rebel Starter Kit

Enter your email and we’ll send it right over.

  • The 15 mistakes you don’t want to make.
  • The most effective diet and why it works.
  • Complete your first workout today, no gym required.
  • These are the tools you need to start your quest.