Can Diet Coke Make You Fat?

There seems to be a lot of confusion out there regarding whether diet soda drinks, e.g. Diet Coke, can cause weight gain.

Check out this email from Kathryn:

“Hey Russ! I’ve lost 25lbs so far but there’s a guy at work who says I’m “ruining my diet” by having a Diet Coke at lunchtime. Is this true? I absolutely love my can (please don’t take it away lol), but I don’t want to ruin it. What’s the truth?”

– Kathryn

I’ve got some good news and some bad news.

The good news is that Diet Coke will not ruin your diet and will not cause weight gain, so you can continue enjoying it without fear. The bad news is that this news won’t stop the know-it-all guy from your office talking shit, because people be dicks.

Why Diet Coke Doesn’t Cause Weight Gain

Something which has zero calories cannot cause weight gain.

Now, some people will claim that “the sweetener in Diet Coke (aspartame) will trick your body into thinking it’s had sugar and force it into fat storage mode!” but this is also wrong; first because there’s never been a study where the body responded to aspartame in this manner, and second because if something contains zero calories then there are zero calories to store.

So there you go, enjoy your lunchtime Diet Coke!

I personally don’t like the taste of it (I’m a Pepsi Max guy), but I know that one of the biggest dieting mistakes people make is to remove the small things which they really enjoy, like this, so pay no attention to the guy at work. (11, 12)

Are There Any Studies Which Directly Show Tat Diet Coke Causes Weight Gain?

There are none.

And I’d be pretty interested if there were, too, because this would be the first time in human history where the law of thermodynamics (calories in versus calories out) has been broken.

In fact, what we have in terms of academic research on this topic actually shows that not only will it have zero impact on weight gain, but diet soda can actually be a useful tool for helping people stick to their nutrition plans.

A 2009 study published in the Journal of Endourology confirmed that diet soda drinks are not harmful to body composition. They also won’t slow down your metabolism, as per a trial published in the American Journal of Clinical Nutrition, and a fascinating research paper from the University of Texas even showed us that diet soda drinks have zero impact on weight gain or weight loss mechanisms (the same as any other zero calorie beverage). (9, 10, 11)

The Texas study is really cool, because it answers multiple questions on this topic for us.

For example, you’ll often hear folks say, “Oh, it’s not about the calories, it’s the other stuff in there which makes you get fat!”, which is an absolute clusterfuck of a statement, but if that was really the case those markers would’ve shown up during a trial which compared diet soda drinks against other zero calorie drinks. Spoiler; there was no difference!

What About Studies Which Show “A Link” Between Diet Soda And Obesity?

This is where the water gets a little bit murkier, because people often confuse correlation with causation.

When research shows a link (e.g. this guy drinks Diet Coke and he’s also fat), this is classed as correlation.

It’s easy to see why people would make an incorrect correlation with regards to diet soda drinks and obesity because overweight people make up the lion’s share of of consumers.

Of course, that’s because a) they are the target market for these drinks, and b) many of them switched to diet soda from regular soda in a bid to reduce their calories.

I hate correlation, because it leaves the door open for research to be twisted. For example, the number of murders in New York City and ice cream sales peak at the same time of year, so does that mean people are going batshit crazy over Mr. Whippy?

Of course not!

(Okay, maybe if you stole ice cream from this kid!)

… But What About This Popular Infographic?

This picture has been floating around for years, and it makes a simple can of Diet Coke look like 330ml of death.

My regular readers know that I despise fearmongering tactics like this, so I’m going to debunk this shit-show to end the article today.

• Claim 1: “Diet Coke switches your body into fat storage mode!”

This is dead wrong.

During the 1980s people worried that sweeteners like aspartame might “trick the body into believing it has just received sugar” and that this would lead to an insulin spike, which would trigger fat storage, but science has since shown us that’s not true – the only thing which can trigger fat storage is eating too many calories! (1, 2, 3, 4, 5, 6)

• Claim 2: “The potentially deadly combination of caffeine and aspartame creates a short addictive high, similar to the way cocaine works!”

Holy mother of fuck.

They are referring to the brain’s reward centre, which obviously cocaine would stimulate. Oddly enough, there’s no evidence to suggest that caffeine stimulates this part of the brain, but it’s worth knowing that other daily activities like exercising, eating food, and watching those YouTube vids where people try to decide if it’s “real or cake” also stimulate the brain’s reward centre! (7)

Furthermore, we could use the term “potentially deadly” on anything at all. Heck, I could make my pre-workout potentially deadly if I decided to drink the entire tub, or even a bottle of water if I decided to drink until it got dark outside.

Because it’s all in the dose, right?

So it’s worth knowing that in order for caffeine and aspartame to become deadly you’d need to drink over 1200mg/day caffeine and 3880mg/day aspartame for a sustained period of time, which translates to a whopping 22 cans of Diet Coke per day! (8)

• Claim 3: “Routine consumption of diet sodas, even one per day, are connected to higher likelihood of heart disease, stroke, diabetes, metabolic syndrome, and high blood pressure.”

If your lunchtime can of Diet Coke had this much power, Thanos would have dropped a multi-pack from space and saved himself the trouble of snapping his fucking fingers.

There is no evidence to support any of the claims made here, and the reason they’ve used the term “connected to” (e.g. correlation) is because it allows them to twist things. As mentioned earlier, obese people make up the diet soda drinking demographic, so most of the studies on diet soda feature obese participants, who have higher risk factors which were not caused by diet soda.

• Claim 4: “Diet Coke will attack the enamel on your teeth!”

This one is true.

You’re an adult and you probably already know that drinking soda is bad for the enamel on your teeth, so don’t be a dick. (13)

Russ’ Take-Home Advice

I don’t want to give you the idea that Diet Coke is good for you, or healthy, because it’s not.

I mean:

• It serves no nutritional purpose other than tasting nice.
• It won’t improve your performance in the gym.
• It won’t make you perform better in a sport.

That being said, there’s no reason for you to give it up – especially if you find that it quenches your sweet tooth and helps you stay consistent with the rest of your nutrition plan.

So there you have it; your can of Diet Coke doesn’t need to be a can’t of Diet Coke!

Further Reading:

If you enjoyed this blog, then you’ll probably also like reading these.

>> The Rules To Ripped
>> Why I Ditched Clean Eating
>> The Detox Industry Is A Dumpster Fire Of Misinformation

References:

1. Smeets P. A. M., et al. Functional magnetic resonance imaging of human hypothalamic responses to sweet taste and calories. Am J Clin Nutr (2005).
2. Møller S. E., et al. Effect of aspartame and protein, administered in phenylalanine-equivalent doses, on plasma neutral amino acids, aspartate, insulin and glucose in man. Pharmacol Toxicol (1991).
3. Wolf-Novak L. C., et al. Aspartame ingestion with and without carbohydrate in phenylketonuric and normal subjects: effect on plasma concentrations of amino acids, glucose, and insulin. Metabolism (1990).
4. Horwitz D. L., et al. Response to single dose of aspartame or saccharin by NIDDM patients. Diabetes Care (1988).
5. https://academic.oup.com/ajcn/article/82/5/1011/4607445/
6. Howell S., et al. “Calories in, calories out” and macronutrient intake: the hope, hype, and science of calories. Am J Physiol Endocrinol Metab (2017).
7. Nehlig A., et al. SPECT assessment of brain activation induced by caffeine: no effect on areas involved in dependence. Dialogues Clin Neurosci (2010).
8. Andrew G., et al. Sweet-taste receptors, low-energy sweeteners, glucose absorption and insulin release. Br J Nutr (2010).
9. Passman C. M., et al. Effect of soda consumption on urinary stone risk parameters. J Endourol (2009).
10. Maersk M., et al. Sucrose-sweetened beverages increase fat storage in the liver, muscle, and visceral fat depot: a 6-mo randomized intervention study. Am J Clin Nutr (2011).
11. Nettleton J. A., et al. Diet soda intake and risk of incident metabolic syndrome and type 2 diabetes in the Multi-Ethnic Study of Atherosclerosis (MESA). Diabetes Care (2009).
12. Shenkin J. D., et al. Soft drink consumption and caries risk in children and adolescents. Gen Dent (2003).
13. Koliaki C., et al. Defining the Optimal Dietary Approach for Safe, Effective and Sustainable Weight Loss in Overweight and Obese Adults. Healthcare (Basel) (2018).