Welcome to my science based guide to drinking water for weight loss.
After reading my guide all the way through, you'll know exactly what happens if you stop drinking water altogether, if you start drinking less of it, or if you begin to drink more of it.
You'll also find out exactly how much water weight you can lose really quickly (in 2 hours) and whether or not any of this will actually help you get rid of that stubborn body fat.
Before we get started, here's a quick overview of everything you can expect to learn from this guide:
How much water weight can you lose in 2 hours?
To bring home a solid number on just how quickly it's possible to lose water weight, I did a 7.5-mile (12-kilometer) hike.
It was a hot summer day and the hike took me about 2 hours. Naturally, to see how much water weight I'm going to lose, I didn't bring any water with me.
(I don't suggest you ever try this, because the thirst and the heat can really start getting to you after an hour or so.)
Naturally, I weighed myself just before the hike and right after the hike.
And my weight loss results were pretty amazing: I lost a whopping 3.3 pounds (1.5 kilograms) in just two hours!
Did I lose any body fat with all that water weight?
Yes, I lost a lot of water weight by not drinking water and sweating a lot (because I did my hike on a hot day).
But as far as actually losing body fat goes, we have to look at how many calories I actually burned.
The hike took me about two hours and given my weight, I probably burned a little over 700 calories.
So in total, I lost less than 100 grams of body fat. Compared to how much water weight I was able to lose (15 times as much), that's a disappointingly small number.
This brings us right to the next question...
Should you stop drinking water to lose weight?
Most definitely not. If you stop drinking water to lose weight, then yes, the number on your bathroom scale will start dropping pretty quickly, but...
You'll also be putting your own health in danger. Losing too much water weight causes your body to become dehydrated, and if taken to extremes, dehydration can actually lead to heart failure[1].
Besides, no matter how much water weight you might lose if you stop drinking water, this will do absolutely nothing to help you lose any of that stubborn body fat.
Ok, so to totally stop drinking water to lose weight would be out of the question. But what about if you simply started drinking less water than usual?
Does drinking less water cause weight loss?
Yes, unless you're currently drinking way too much water, drinking less water will help you lose some weight.
But again, we're only talking about losing some water weight temporarily, without actually losing any of that ugly belly fat at all.
And as you're about to see, science says drinking less water can't really help with weight loss in the long run.
In fact, drinking less water might actually slow down your weight loss progress.
So let's take a closer look at the science that explains why drinking less water might not be a good idea if you want to lose some extra body fat.
Can you lose weight by drinking water?
In one study[2], they proved that drinking down 500 ml (or 6 fl oz) of water boosts your calorie burn rate by 30%!
Granted, this metabolism boost doesn't stick around the whole day, but it still proves drinking water can actually help you lose weight.
So, instead of dehydrating yourself to temporarily lose some water weight, drinking enough water throughout the day should help keep your metabolism revved up.
(Which in turn leads to the ultimate goal of all smart weight loss efforts, body fat loss.)
Let's take a look at how much water you actually need to drink every day, whether you're trying to speed up weight loss or not.
How much water do you need to drink for weight loss?
I've looked at a couple of different studies, and none of them told me exactly how much water you need to drink for weight loss every day.
But the general "rule of thumb" you can follow, is about 3 liters (about 13 cups) for men and 2.2 liters (about 9 cups) for women.
But bear in mind, this is a very general recommendation and that there are many other things that can increase your daily needs for water.
A hot environment, how active you are, certain health conditions...all of these things can make you have to drink a lot more water than the average person.
Also, you don't actually need to drink water to get enough water in your body.
How to replace the lost water weight without drinking water
After my 2-hour hike, I "owed" my body about 1.5 liters (about 6 cups) of water. But instead of actually drinking water, I ate a half of a watermelon.
I am a huge fan of watermelons, especially when it's hot and I'm really thirsty.
I don't even cut them into slices, I just split them in half and eat them with a spoon.
This half of watermelon weighed exactly 5.5 pounds (2.5 kilograms) without rind.
By eating the entire half (throughout the day), I also got in about 2.2 liters (about 4 cups) of water.
(I explain all about why watermelons can be so awesome for weight loss in my science based guide to losing weight with watermelons.)
In other words, I more than recovered any body water I lost during the hike, without actually drinking any water.
What kind of weight loss results can you get from drinking water?
If you're ready to commit to drinking (more) water every day, here's the kind of weight loss results you can expect:
In one study[2], smart scientists calculated that drinking 6 cups (1.5 liters) of water can help you burn off 17,400 extra calories per year.
So on top everything else you'll be doing, drinking water regularly can boost your weight loss results by 5.3 lbs (2.4 kg) per year.
That's at least 5.3 lbs (2.4 kg) of pure body fat per year you'll lose (keep off), if you simply commit to doing what you already should be doing, even if you're not trying to lose weight.
Summary (actionable takeaways)
As you saw, science agrees with me when I tell you that drinking water for weight loss is a smart idea.
If you wanted to stop drinking water altogether, or even started drinking less water to lose more weight, you now know this will actually put the brakes on your metabolism.
Staying away from water will help you temporarily lose a pound or so of water weight (at best) and will cause dehydration and some health problems connected with it (at worst).
So do yourself a favor and drink water regularly to keep your body nicely hydrated and your fat metabolism properly revved up.
References
Written by Rok Sprogar, CNC, WLS
Rok Sprogar is a NASM Certified Nutrition Coach (NASM-CNC) and a NASM Certified Weight Loss Specialist (NASM-WLS) who has been contributing highly actionable and science-based content to Leanhigh.