Will Diet Coke make me gain or lose weight in the short term?

August 8, 2006 12:39 AM

Any jockeys or prizefighters in the house? I've read repeatedly that Diet Coke and other diet soft drinks have both sodium - which makes the body retain water - as well as caffeine - which acts as a mild diuretic. Which effect is greater? Will drinking a diet soda cause a net gain or loss in your weight a few hours later?

First off, I'll admit that this is totally prompted by an upcoming Weight Watchers weigh-in. I'm not trying to game the system, but I would like to be sure I'm not going in there carrying any extra weight. It sure seems like when I have a Diet Coke (after drinking normal water), I end up going to the bathroom a lot more often. So in a hypothetical situation where you wanted to weigh-in as light as possible, would it be better to A) just drink water, B) drink water and a bit of caffeine, or C) drink nothing at all? I've done some Googling and while I can find references to both the "water retention" and "makes you pee more" effects, I can't find anything that suggests whether they cancel each other out.

I'd just like to stress that I know Diet Coke isn't healthy and if I were a truly good person (that was sarcasm), I wouldn't drink it at all. But dammit, I've lost nearly fifty pounds in the past year and I need to feel like I have one tiny vice left. I've just always wondered whether I should cut it out on Weight-In day or not. (I know that the net effect is likely to be miniscule, and I'm truly not the type to obsess about 100g... but I just wondered.)

posted by web-goddess to health & fitness (13 answers total)

Diet coke makes you pee more, but I suspect you won't actually dehydrate yourself on it - you'll only pee out more of the coke you'd drank than the amount of water you'd pee out if you drank the same quantity of water. It'll be, I think, a net gain to drink diet coke, but less than if you'd drunk something with no caffeine in.

The thing I've known people who have to weigh in below a certain weight is drink nothing and do sweat runs or some similar exercise. This is generally not a good idea though, and you don't want to overdo it. This is only a Weight Watchers weigh-in after all.

If I were in your position I'd minimise the amount I drank. If you find yourself particularly thirsty then do drink some water, just maybe consume it in smaller amounts so you don't rollercoaster to being very hydrated.
posted by edd at 12:59 AM on August 8, 2006

Seriously....if you want weigh-in less, just go for a run and take a ephedrine-caffiene stack or something.

If you want to be healthy, drink diet pepsi if you like it and don't drink sugar soda. And don't worry so much about individual weigh in's if the overall trend is going down.
posted by rsanheim at 1:07 AM on August 8, 2006

You're not trying to game the system... but you are trying to game the system.

I am not a doctor, and this is not medical advice. It is not good for you.

Drink only water for one day leading up to the "weigh in"... have a bowel movement... then, 8 hours before, no fluids, no nothing.

Buy yourself a Sauna Suit from any sporting goods store... during your 8 hour water fast... run, spit, suffer... for the 8 hours leading up to it.

Weigh in and look at the faces of the dejected (but rule-abiding) fatties around you.

This regimen would routinely cut 5-7 lbs off of me as a 140#, 6% body fat high school 'rassler... Losses of up to twice that could be achieved by larger folks carrying more water.
posted by cadastral at 3:19 AM on August 8, 2006

Whoa! I'm not trying to knock off 7 pounds... I just want to know if my Diet Coke is helping or hurting the bottom line. I'm not really looking to *add* anything to my routine, especially when it sounds as miserable as running around trying to sweat every drop from my body. Especially since I'd have to keep it up every week (or else register a gain)!

I just got home from the weigh-in and had an 800g loss this week - which since I skipped last week's meeting, is actually over two weeks. So that's about a pound per week and that's great. This question was more to satisfy my intellectual curiosity than to solicit ways to cheat the scales. :)
posted by web-goddess at 3:30 AM on August 8, 2006

Well... the regimen I just suggested might sound a bit extreme...

By way of directly answering your question... vis a vis your "A, B, C" breakdown...

The answer is "C" (duh). How could following "A" or "B" possibly make you weigh less than following "C"?
posted by cadastral at 3:43 AM on August 8, 2006

Well, obviously if the diuretic effect of a Coke makes you lose *more* liquid than just the Coke itself. I have no idea how it works. That's why I'm asking.
posted by web-goddess at 4:22 AM on August 8, 2006

I drink >100oz of diet Mountain Dew per day and have lost more than 100lbs. I also pee it out through about 20-30 trips to the bathroom per day.
posted by drkrdglo at 5:12 AM on August 8, 2006

As a side caveat, a trainer I know told me of a customer who was just starting to work out. The trainer gave him a light workout and told him to drink plenty of water. The customer translated 'water' to 'fluid' to 'diet coke', which was his normal drink. Despite the light workout (about 20 minutes on a stationary bike), he went into renal failure.
I know this is an extreme, anecdotal case, but the results are worth noting.
posted by dragonsi55 at 5:27 AM on August 8, 2006

go to any serious gym and score some diuretics from the weight lifters, they pop them like candy
posted by matteo at 6:25 AM on August 8, 2006

I don't have references, but (I swear) there was a study within the past few years which sought to answer just this question (although it was from the standpoint of hydration). The determination was that there was a net gain of fluid, but that the diuretic affects of caffiene made it only half as much as drinking water. In other words, 16 oz of diet coke=8 oz of H2O.
posted by OmieWise at 7:08 AM on August 8, 2006

Well, here's a review of one of the studies I'm talking about, which claims that the diuretic affects are negligible.
posted by OmieWise at 7:11 AM on August 8, 2006

IANAD, but it seems to vary from one person to the next. Some diets say to avoid caffeinated beverages. They don't seem to bother me. I've found that alternating drinking actual water with diet beverages (my beverage of choice being caffeine-free Diet Coke) *does* help me post good numbers on the scale. Your mileage may vary, of course.

Congrats on your weight loss. And don't worry about the diet drinks.
posted by wheat at 8:32 AM on August 8, 2006

Thanks, OmieWise. I guess that study is about as close to an answer as I'm going to get, and it seems pretty straightforward: "When caffeine or a caffeinated beverage is consumed, the body retains some of the fluid." Also says that regular drinkers have a higher tolerance, so I might not even be getting the full diuretic effect. So obviously having a Diet Coke on weigh-in day is going to result in some gain, though less than drinking just plain water.

(Incidentally, what's up with all the "answers" that are just anecdotes that didn't even try to answer the question? Bad form!)
posted by web-goddess at 2:42 PM on August 8, 2006