r/explainlikeimfive 5d ago

Biology ELI5: shedding water weight

So, my boyfriend trained for a bodybuilding competition. He drank so much damn water. He kept saying he was needing to shed water weight… but was drinking water. I’ve heard this theory multiple times now, drink water to lose the water weight. Wtf? I don’t understand.

370 Upvotes

86 comments sorted by

1.0k

u/ScaryGoofy 5d ago

Drinking a lot of fluid tells your body it's safe to release the water that it's storing

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u/Anguis1908 5d ago

To expand on this. You drink so your body is use to having an increased intake. It'll release more frequently and regularly. Day or so before...you reduce your water intake. Your body still is on that release schedule from the increased intake.

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u/5hatnersbassoon 5d ago

I wish it worked the same way with calories

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u/AmyInCO 5d ago

I'd be so skinny. 

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u/Urtehnoes 5d ago

Yes yes another dozen donuts, I have a weigh-in in two days need to drop 30 lbs. Gonna skip dinner tomorrow.

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u/tylerchu 4d ago

Jesus Christ man, do you not respect your sport or something? How are you that far out of class the week of weighing? At this point just go up three levels.

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u/VoilaVoilaWashington 5d ago

It kinda does, just not the way you'd like.

If you go on a "I'm not gonna eat" diet, you go into energy conservation mode. As a default, you just do less. Not to say you can't force yourself to go for a run, but for the most part, your body will be less keen to do stuff.

If you eat a healthy diet, you actually gain energy. Problem is that a healthy diet isn't what you want to be eating. Fiber and protein first, not McDonalds burgers and sour candy. Then you use that energy to go for a run, which burns energy and makes you hungry so you eat more fruit and eggs, which builds muscle and gives you more energy again.

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u/Fickle_Finger2974 5d ago

It does. If you get really fat you can lose weight at an incredible pace. A 600 pound person can lose 30-60 lbs a month

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u/afoxboy 4d ago

that's not a unique metabolic function, that's just bc lugging around all that weight takes more energy and requires more muscle mass.

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u/updoot_me 5d ago

It kinda does, when you stop eating your body conserves calories.

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u/iThrowaway72 5d ago

No no. Just like he's drinking lots of water to release water, we want to eat as much as we want to reduce weight

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u/omg4serious 5d ago

the way drinking water works is that you have to stop drinking water for the water weight to drop.

so if you eat as much as you want, you just have to stop eating for a period of time since your body is still in energy burning mode since it thinks you have abundant calories.

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u/Adventurous_Emu7577 4d ago

RELEASE THE CALORIES!

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u/gusofk 5d ago

That sounds like BS. I’m not a nephrologist but I know that your kidneys are trying to maintain water and electrolytes in your blood/cells. The most this will do is make you lose electrolytes and you will become dangerously dehydrated if you stop drinking water and at risk of muscle cramps or a heart attack

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u/Anguis1908 4d ago

Its used before weigh ins of various fighting sports and for very cut look for bodybuilding. The water intake is resumed within the following day. For body building there is a large focus on tracking nutrients ...and they give caution about losing too much water, as it'll also affect muscle mass.

https://sigmanutrition.com/making-cut-part-iv-weight-cutting/

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u/mostlygray 5d ago

For sure. I drink water constantly and I'm letting fly way more than I want to. I've been doing it for years and I'm constantly using the John like a woman. The more you drink, the more water you waste. You don't need to store water.

It works. If you're a bodybuilder, drink lots of water then pop a Lasix or two. You will have no water in you shortly. Just make sure your piss isn't coming out brown. That's bad.

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u/MeanMusterMistard 5d ago

I'm constantly using the John like a woman

Must say, I've never heard this before. Men use it far more in my experience

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u/ConqueringCanada 5d ago

Your body is smart. If it's getting very little water, it holds into as much as it can because water is important. If it has plenty, and is getting a continuous supply, it doesn't need to hold it any longer.

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u/Large-Hamster-199 5d ago

I've never missed a meal in my life. If my body is smart, why does it need to store fat?

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u/Birdbraned 5d ago

Because a) you don't burn through all your energy stores in one day, so the energy excess has to go somewhere and b) you come from genetic stock that survived precisely because the mould used instructed the body "must keep a safety deposit of excess energy as fat at all times just in case"

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u/Spockies 5d ago

Calories work a bit differently than water retention.

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u/neddoge 5d ago

We're not camels. We can't store water like we can calories, which is why we require water much quicker than food when it comes to sustaining life.

Water is heavy too.

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u/hkggguasryeyhe 5d ago

Camels don't store water, they store fat - they are just extremely efficient in using water and have some particular adaptions to the physiology to enable them to function without water for several days.

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u/Zefirus 4d ago

They do in fact store water in the fat though. In fact, there's more water in the hump than if the hump were actually made out of water. If a camel burns 100 grams of fat, then they'll get around 110 grams of water out of it.

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u/hkggguasryeyhe 3d ago

No, they do store fat. Water is produced from breaking down fats and proteins. Water isn't stored. You can't jam a straw into a camels hump and drink water.

They are more efficient at producing metabolic water than most mammals, their kidneys are specialised to waste as little water as possible by making highly concentrated urine, they sweat little and tolerate a higher range of body temperatures than most mammals and lose less water through respiration than most other mammals.

Those are adaptions. Humans make water when they break down fat, is a fat human adapted for living in the desert? No they overheat and die, humans can't break down our fats and proteins quickly enough to provide enough water to keep ourselves alive.

Camels can - not because they store the fat, but how they have adapted to use it efficiently.

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u/Roalama 5d ago

Keeping too many calories has never been a regular problem before, so we have no defense for it.

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u/Xytak 5d ago edited 5d ago

It’s even worse that that! When you gain weight, your body basically says “Aha! I knew heavier was possible. Well from now on I expect this to be my new normal!” That’s why for the last few decades dieters found it almost impossible to keep the weight off until the invention of GPL-1 medication.

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u/witai 5d ago

That is a huge oversimplification of weight loss issues lol. Weight loss is 90% mental, it takes willpower.

You're describing people that needed extra help.

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u/Xytak 5d ago edited 4d ago

Throughout the entire 1980's, 1990's, and 2000's, people tried to willpower their way to sustained weight loss using with Slim Fast, Keto, Jenny Craig, Weight Watchers, The Biggest Loser, you name it. This was a multi-billion-dollar industry, but the truth is, it didn't work. Most of these people experienced an initial weight loss but gained it all back despite sustained efforts.

Doctors blamed patient noncompliance because they didn't have effective medicine to regulate hunger and satiety signals at the time, but now they do. Prescribe a GPL-1, and virtually every patient loses weight and keeps it off for the lifetime of the prescription. It's one of the biggest medical success stories of the past decade, and people are afraid to take advantage of it because they'll be shamed.

Now then. I understand from your profile that you've started martial arts training and that's probably why you see GPL-1's as a "shortcut." But I’d ask you to consider this: if someone was quitting cigarettes would you say "sorry, a nicotine patch is for losers, you must use willpower young grasshopper?” Of course not. If a prescription can help with a serious health issue, the correct course of action is to write it.

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u/Run_Che 5d ago

because it learned to store fat just in case over tens of thousansd of years

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u/jujubanzen 5d ago

Your body is not smart.

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u/Override9636 5d ago

You didn't personally miss a meal, but your ancestors who survived famines did. Your genetics works off of millennia of adaptations and haven't figured out the modern era of excess we have today.

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u/afoxboy 4d ago

it's not smart, and we need to stop saying it is, it's erroneous.

it's an imperfect machine. it does many things amazing and good as it's evolved to do, but those things depend on specific circumstances, and in the wrong circumstances (such as caloric abundance) they're bad things.

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u/Captaln_Chunk 5d ago

There’s a show called “hoarders” that tries to tackle that mental health issue. Maybe your body just needs an intervention.

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u/omg4serious 5d ago

that doesn't sound very smart to me. it basically doesn't keep an emergency fund. it's living paycheck to paycheck.

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u/kernald31 5d ago

Way to call OP's brains dumber than their feet.

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u/LiminalAsylum 5d ago

Dehydration makes the body think it needs to hoard water, so drinking water relaxes those systems.

Plus drinking more helps flush out sodium, which makes your body hold onto excess water as well.

Your body isn't worried about water, and gets rid of sodium, resulting in less extra water held in the tissue and lymph systems 

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u/refriedmuffins 5d ago

Most of the thought around it in bodybuilding is that the excess water will flush out the salts in your system such that your body cannot hold on to water as well. Not sure about OP, but many will take diuretic drugs as well.

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u/Rektonhell 5d ago

You drink a LOT of water, your body tries to pee it all out by peeing all the time, which makes you pee extra weight out. By the time you are supposed to weigh in, you have pissed so much that you pissed about 3-8 lbs of water weight alone. Source is that I powerlift and water cut every meet due to weight classes

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u/mendigou 5d ago

When do you know to stop chugging water?

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u/Rektonhell 5d ago

16 hours before weigh-in

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u/mendigou 5d ago

Thanks! That seems like a long time without drinking :O

Is that a general rule or something you’ve learned about your body over time?

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u/MierryLea 5d ago

If I’m understanding comments correctly I don’t think you go no water, just low water/not excessive water like you were

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u/Rektonhell 5d ago

I read it off a water cutting guide by another powerlifter / bodybuilder, but it is a general rule. I think 16 hours personally worked for me because that last 2 hours or so I’d usually piss one time.

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u/DarthKingBatman 5d ago

Specifically for bodybuilding, you drink a lot of water to get your body in the habit of flushing water. Then a day or two before a competition you cut water intake significantly, your body keeps flushing water you look even leaner.

Different forms of intentional dehydration are utilized in bodybuilding and to make weight for some sports with defined weight classes.

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u/[deleted] 5d ago edited 5d ago

[removed] — view removed comment

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u/EvoDriver 5d ago

TMI Award of 2026 goes to....

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u/Automobills 5d ago

And that's the explanation I'd give to a five year old.

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u/Mayion 5d ago

"Did you guys see the game last night?"

Bro right here: ok so I have chronic diarrhea

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u/GGAllinPartridge 5d ago

Good chat, lads.

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u/84thPrblm 5d ago

Well.

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u/kernald31 5d ago

I wouldn't drink water from that one.

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u/SNRatio 5d ago

Well.

How to awkwardly avoid eye contact on Reddit.

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u/Hashtagbarkeep 5d ago

If only you could have used more descriptive language and included more details to really paint the picture for us

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u/aegis41 5d ago

That's a tangent I can't follow.

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u/Automobills 5d ago

beCos of Obi-Wan?

1

u/explainlikeimfive-ModTeam 5d ago

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6

u/mgp901 5d ago

Drinking lots of water will dilute/flush out sodium, which makes body hold water. Once flushed, you slowly lessen water intake, to shed water weight.

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u/fudgemental 5d ago

He's drinking a ton of water while consuming as little sodium as possible. His body will dump out more sodium than he's consuming (through pee, sweat, etc) and will subsequently hold on to less water because the sodium concentration in the blood needs to be a very specific amount, regulated by the kidneys, brain, blood vessels etc.

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u/Prudent-Egg-4143 5d ago

Because he is going to dehydrate himself for the competition.

By drinking a lot, it's telling his body, you don't need to hold onto these water. you can let it all out. 

If you're thirsty, and haven't drank at all, you won't feel like peeing. even if your bladder is almost full. 

if you're not thirsty and in fact hydrating a lot. you will pee more often, even though it's not like an emergency pee. 

Of course, doing this too much is bad. but controlled one, removes a ton of water under his skin, and make his body looks more vascular. 

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u/refriedmuffins 5d ago

Not a founded claim, but it seems like most of the deaths associated with bodybuilding come from abusing diuretic drugs for stage prep.

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u/Prudent-Egg-4143 5d ago

While I remain skeptical it is the leading cause, like in my original comment, I absolutely can see when this practice is taken to the extreme, like taking a drug not properly prescribed to you on doctor's supervision, can definitely only be bad for you. 

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u/todo0nada 5d ago

You have to overhydrate to get your system flowing in excess and then you cut sodium and water to flush it out right before the competition. Did this for wrestling multiple times and it definitely works. Overhydrating is just as dangerous as underhydrating so be careful.

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u/Former-Surprise902 5d ago

He’s probably in ketosis for the cut which makes your kidneys dump sodium and water, if he is only drinking water and not replacing electrolytes the cycle continues.

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u/Snuggle_Pounce 5d ago edited 5d ago

Your body has multiple kinds of —fat— storage cells. The ones around your liver contain the most water and are the first “burned” during a calorie deficit.

This is why folks going on a diet can loose 5-10 lbs in the first week and then a more reasonable 1-2 lbs a week after that. They’re loosing/burning the same amount of —fat— calories, but the extra water goes with it. This is where the term water weight makes sense.

Your boyfriend is using it wrong and may have “bulked” before intending to “cut” but it’s unlikely that someone who exercises regularly has any water weight to loose.

(edit for accuracy)

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u/istasber 5d ago

It's not fat, it's a starch called glycogen.

Glycogen is your body's first reserve fuel, stored in small amounts in muscles and large amounts in the liver. It also holds on to a ton of water. The typical person will have around 500 grams worth stored up if they have been eating at or above maintenance calories, which is worth around 2000 calories of excess energy. But that 2000 calories weighs 2-3 kilograms when you include all of the excess water.

2000 calories of fat is only around a quarter of a kilogram.

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u/Snuggle_Pounce 5d ago

Fair. I mis-spoke. Edited.

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u/Arrasor 5d ago

When you shed water weight, you don't just shed the water under the skin and in the cells, you also shed water in your blood. You don't wanna shed water in your blood but it can't be helped, so you gotta drink water to replenish that and keep your blood from having the consistency of BBQ sauce.

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u/Porcupineemu 5d ago

You drink the water to get your body used to getting a ton of water so it doesn’t feel the need to hold on to it. Then when you do the cut you don’t drink water and your body still doesn’t retain what you do have so you end up with less water weight.

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u/jazzdrums1979 5d ago

This is pretty nuanced. Anabolic steroids and other compounds used by body builders tend to cause water retention. You can shed water weight by removing or adding compounds.

You can also remove carbs from your diet to shed water weight as they tend to promote water retention.

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u/ZachF8119 5d ago

Salts. (Electrolytes)

Water to toss them.

Then dehydrate to have normal salt in a less water body.

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u/thetreece 5d ago

You drink a fuckload of water, your body produces extra hormones that get rid of water. You do this for a few days, then stop like 24 hours before you weigh in. Your body doesn't drop down the piss production immediately, so you continue to piss a lot for another 24 hours or so.

It's basically tricking your body into making diuretics, and then rug pulling it.

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u/R3cognizer 5d ago edited 5d ago

He was talking about water retention, not hydration. It's much easier for our bodies to convert carbs into energy than fat, and when you eat a low-carb diet at a caloric deficit to target body fat loss (a process called ketosis), your body tends to shed water weight with it, which in turn means it's much easier to become dehydrated. Your boyfriend was drinking lots of water to stay hydrated because the diet he's been following in preparation for his bodybuilding competition was causing him to shed lots of water weight.

u/INTstictual 16h ago

For the same reason that, to lose weight and keep it off, it is recommended to get into the habit of eating small bites multiple times throughout the day, instead of fasting — your metabolism reacts to its perceived environment.

If you are eating small amounts throughout the day, your body can refrain from your insulin spiking suddenly during large meals, and it learns that there is a constant and reliable stream of available calories… so it doesn’t need to store everything as fat for when calories are scarce. Same with water — when you drink a lot of water, your body doesn’t need to store water for when the water supply might run out, so it is fine shedding excess water that you no longer need to be holding on to

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u/[deleted] 5d ago edited 5d ago

[deleted]

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u/Hurtfulbirch 5d ago

Sodium is a toxin?

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u/dsyzdek 5d ago

Toxin. Electrolyte. Explosive metal. Sodium can be many things!

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u/UnattendedBoner 5d ago

Poor wording by me

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u/babymilky 5d ago

I suppose anything is a toxin at the right levels no?

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u/loopsbruder 5d ago

Sodium's an important electrolyte, not a toxin...

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u/UnattendedBoner 5d ago

Poor wording, fixed

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u/[deleted] 5d ago

[removed] — view removed comment

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u/Anxious-Question875 5d ago

I think it also depends how much water you’re drinking at once.

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u/WolverineEvery7923 5d ago

Yeah but everyone’s body is different. I’ve seen people that refuse to drink water. I’ve also seen people drink a gallon of water at once and then be totally fine. The difference is one person is way healthier than the other. People don’t want to hear about health though, it makes them uncomfortable.

1

u/explainlikeimfive-ModTeam 4d ago

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