What is the deal with "water weight"? (and other mysteries explained. 

Things that I learned while researching “peak week”, that everyone should know. 


 When I was at my MOST lean, ( think, 12% body fat if you include organ body fat, but closer to 4% if you only count subcutaneous fat) it wasn’t as though I had a lot of “fat” left to lose. However, I was still having major problems with my bathroom scale. People looking at my competition pictures keep asking me how much I weighed when I competed, and I have to honestly say, I don’t really know. This is because in any given week, my bathroom scale would fluctuate up to SEVEN POUNDS , depending on a number of factors. (so I would either weigh 120- 127.) which is a significant difference, anyway its looked at, and there is no way that i even had 7 lbs of fat left to lose at that point. And it would actually do so OVERNIGHT- I would go to bed weighing 129, and wake up weighing 122. (and spend all night peeing, incidentally).

  After observing this consistently for a few months leading up to competition, I started researching it. Ultimately, the results of the research let me to a very deep understanding of that annoying “its just water weight” statement. 


In order to learn about water weight, we have to first learn about carbohydrates, and how the body metabolizes them .

Fell asleep during biology 101? well, here is a (hopefully) relatively easy to follow summary for you: 

 When you eat, you ingest three things: fat, protein, and carbohydrates. (we are ignoring alcohol for the time being :)

Carbohydrates are all things that can be broken down into a sugar- regardless of whether it is a green leafy veggie, pasta, or candy. The only way a body can use them is by converting them into a sugar- namely, glucose. 1 Glucose is what the body uses for energy. It is necessary for life: Your brain ONLY uses glucose to function , whereas muscles can use glucose, fatty acids and ketone bodies. 2

 So, you eat a carb. your digestive system breaks it into a simple sugar and it is absorbed through the intestine into the blood stream. Then it is converted into glucose, and then stored in two places: 

1 in the liver, and 

2 In the muscles. 

 Unfortunately, the body can’t just store glucose molecules individually. It has to bind them together to form a multi branched polysaccharide called glycogen.(this is done by a process called glycogenesis).5

 When you place demands on your body that requires fuel for the cells to run (this includes brain activity- such as studying for a test) your body needs a ready supply of glucose. It initially uses glucose in the blood stream, then goes after the glycogen in the liver. Only once that is depleted will it then go after the glycogen stored in the muscles. 

 Estimated stores are as follows: the blood contains approximately 80 kcal of energy in the form of glucose.. the liver contains approximately 400 kcal of energy. It gets depleted after 8 hours of fasting.  Once these stores are depleted then your body will use the glycogen stored in your muscles.(which stores about 1500 kcal of energy) 3

 Once you completely empty the glycogen stores in your muscles, THEN your body has to use slower, less efficient form of energy- in the form of fat breakdown. (which is what we are all aiming for!!!! hooray!)

So, the biology 101 review is over. What was the point of it all? 

 Well, the thing about glycogen storage in muscle and the liver is that it is stored in something called a “hydrated form”.-Meaning approximately 3 molecules of water are used up every time you store one glycogen molecule. So, water is needed to for glucose storage .If you aren't consuming enough water, it will start to pull it from other systems and cause you to be chronically dehydrated. When you workout and force your body into a state of burning fat, the glycogen is taken from your muscles, liver and fat for energy. When 1 gram of glycogen is pulled out of your muscles to provide fuel for your body, 3-4 grams of water are also pulled out, and you pee it out. 


Well, this is great, but what does it mean? And what is the “takeaway”?

  So- Say you have a typical high or normal carb diet, and you are fairly sedentary. Chances are, your body barely ever touches your muscle glycogen. If your glycogen storages are full, then your body will just continue to convert the excess glycogen into fat, and you gain adipose tissue. 

 Then you start a diet, which is low enough carbs (and calories) that your body is forced to utilize your muscle glycogen storages, AND you are working out, and creating energy demands on your body. 

 For 1-2 days of this program,  your body will likely work at depleting your blood glucose, then your liver glucose, and then after day 2 or so, it will start dipping into your muscle glycogen. To fully deplete your muscle glycogen takes about another 2 days or so. Continuing to workout will keep your liver and blood sugar glucose depleted, so your body has to use your muscle glycogen to run everything else. 

 I found It was really easy to tell I had spent the last 24 hours or so using my glycogen stores, because all of a sudden, I had to pee, all the time. especially at night. And I would wake up LITERALLY 7 pounds lighter.


How can you use this knowledge to your advantage?

 Keep in mind- to use this system, implies that other water affecting homeostatic variables should be kept as constant as possible- Keep your salt intake relatively similar daily. If you do change it, dont change it for more than 2 days, or it will affect homeostatic balance . Keep water intake approximately constant, at about 3-4 litres a day. This will ensure you have adequate water for your body systems to work properly. 

I figured out that I can use this water weight mechanism to judge a few things- it lets me know how much stored energy I have and that can be a HUGE advantage in fat loss.


1 I realized that I need water for everything to run efficiently. without it, the system doesn't run smooth, and it has to work too hard.

2 Don’t be scared if you gain 5-7 lbs when you EITHER start  a fat loss program, or a day or two after you have a refeed day- Imagine that you are getting glycogen stored into your system and use it as an indicator that your muscles are probably strong and you can do a hard workout in a day or two.

3 Because I got so lean (and this is something that everyone does on peak week,) it was easy to tell when I had filled my muscle glycogen storages- my muscles looked plump and full of water. The trick with peak week was to actually overfill your muscle by causing them to starve for a few days, without “spilling over” and causing the glycogen to be stored in the adipose tissue.  BUT because we aren't dealing with peak weeks here, then if you want to stay in a fat burning state, the best thing to do is just never go over the glycogen storage level your muscles can hold, and you will always burn fat tissue.) However, if you maintain a glycogen depletion for too long, your body may freak out and decide you are starving, and try to physically slow your glycogen breakdown, so an occasional “refeed day” when you purposefully overcarb, can stop that feedback loop. 

4 It took my body about 2 days to fully fill up my muscle glycogen after a refeed day. everyone is different but it averages 1.5-2.5 days. Use that as a guideline for really intense high energy workouts. 

5 About 4-5 days after a refeed day, your body should shed water, regardless of the water you drink. THIS is when you are in pretty much total glycogen depletion, and burning fat. those are the days where it is important to eat numerous small meals and don't miss one, because your body (and especially brain) is running basic functions off of only ingested glucose. the rest of your energy is coming from adipose tissue. low level constant state exercise will be the most efficient, but these will also be the days that you will “bonk” easily, when your brain runs out of glucose. You may find you feel that you always have slightly bad breath, (that is mild ketosis). 

6. In glycogen depletion your muscles will also feel a bit stringy and empty, that is normal, but it also means with no reserves to dip into, those are good days to ingest pre workout carbs, such as protein cookies, etc, for those fast blood stream sugars. It is also why you see triathletes and long distance runners sucking back candy and glucose packages at intervals during runs. (something that also never made sense to me, from a health perspective)  

Online references:


2 http://www.ncbi.nlm.nih.gov/books/NBK22436/

3 http://www.humankinetics.com/excerpts/excerpts/the-bodyrsquos-fuel-sources

4 http://ajcn.nutrition.org/content/56/1/292S.abstract

5 http://runnersconnect.net/running-training-articles/cience-of-bonking-and-glycogen-depletion/

-Dr. Guthrie


Dr. Guthrie competed in her first ever fitness competition in 2014, six days before she turned 40. She placed 2nd in Masters and 4th in novice. She tailored her own training. 


Dr. Guthrie specializes in treating sports injuries.

She has over a decade of experience treating all calibre of athletes,  from the weekend warrior, to the ultramarathoner and professional dancer. If you are wondering if she might be able to effectively treat your injury, please do not hesitate to call or text her at (403) 244-6444.

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