How Much Water Weight Will I Lose on Keto?

Meet Gregory, a writer and the brains behind Face Dragons. He's the go-to guy for getting things done. Gregory's been living the digital nomad life in Asia for as long as anyone can remember, helping clients smash their goals. He writes on topics like software, personal knowledge management (PKM), and personal development. When he's not writing, you'll catch him at the local MMA gym, nose buried in a book, or just chilling with the family.

After a long break from keto, I’ve jumped back on the ketogenic diet, and while things are going much better than I had hoped, there have been some surprises. For example, I had forgotten just how much water weight you lose in the first week of keto. Today marks my 9th day back on keto, and after some research, I want to discuss how much water you will lose on a keto diet.

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Before getting into the averages and giving you an amount you may lose, let me share how much I’ve lost since I started the ketogenic diet nine days ago.

I started the diet at 74.5kg (164lbs), and today after nine days, I’m 71.5 kgs.

That’s 3kg (6.6 lbs) lost in 9 days! But, of course, that doesn’t mean I’ve lost 3kg of fat; no, almost all of that was water weight.

Why do you lose water when you start a keto diet?

To understand why you lose so much water weight when you start the ketogenic diet requires a little bit of biology.

When you eat a standard American diet or any diet where you regularly consume carbs, the carbohydrates get turned into glucose in the stomach. Then, they are absorbed into the bloodstream via the intestines. The body uses this blood glucose as energy, and any excess glucose gets stored as glycogen in the muscles and liver.

When you need energy for a strenuous task later and are low on blood glucose, the body will use the glycogen stores.

So when you’re eating a regular diet that incorporates carbohydrates, you have lots of glycogen stored in your muscles and liver. What’s this got to do with losing water?

The glycogen binds to water and not just a little water; every gram of glycogen can bind to 3-4g of water.

So all that glycogen in your muscles is holding on to extra water.

When you stop eating carbs, your body uses all of its stored glycogen to fuel the body, and as it uses the excess glycogen, the water is released and flushed out. Once glycogen stores are depleted, the body starts to go into ketosis.

Many people recommend doing light exercise in the first few days of starting a keto diet to help deplete your glycogen stores.

How much water is it normal to lose on a keto diet?

Healthline reports it as anywhere between 1 pound to 10 pounds. And other sources online seem to line up with this.

“Anecdotally, people report losses within the first week of anywhere from 1 pound (0.5 kg) to 10 or more pounds (5 kg). The larger you are, the more water weight you’re likely to lose after starting keto.”


Eileen M. Gormley, Former mod of (Cyclical Keto Diet), says,

“Depends on your muscle mass. The more muscle, the more glycogen you can hold. Bodybuilders who do CKD (cyclical ketogenic diets, usually six days of keto and one of carb-up) will typically lose between 5 – 10lb after each carb-up for men and 4–6lb for women.”

Eileen M. Gormley

If you want to know how much water you will lose on the keto diet, try it! Most weight you lose in the first five days will be water weight.