Where does "first week water weight" come from/what is it?

Evelyn_Gorfram

I lost 7 pounds this week. However, this is neither a miracle nor a cause for alarm, because I am extremely obese (7 lbs = 2.2% of my starting weight), and this is my first week.

It's first week water weight. This is accepted dieting wisdom, and has been empirically demonstrated by countless new dieters.

But what is it, physiologically? I'm drinking much more than enough water to stave off dehydration, so that can't be it. And I don't think I've changed my sodium intake much, and certainly haven't done so on purpose (FWIW, I'm averaging 2384 mg sodium/day, slightly above my 2300 mg daily goal).

What is it about a sudden reduction in calorie intake that inspires water to leave the body?

mkculs

First, sodium isn't a goal--it's a max. Were you tracking it before you started here? Usually that water weight is due in part to a decrease in the amount of sodium/processed foods you eat. For people who routinely ate out, ate a lot of processed foods, etc, to change to more eating at home, eating fewer processed foods, etc., it means a lot less sodium (among other things, like a lot less fat, too). I don't tend to eat much sodium -- never add salt to anything and don't eat out much--so I never saw that big first week or two change.

JeromeBarry1

Generally, as in the case of me, the first week of logging in a deficit is a week of lesser carbs and fewer salty foods than they had customarily been consuming, as well as some excessive cardio work. The mass of food waste from the prior week, along with the freely discharged water from the lower salt intake, and the freed water from the cardio expenditure of glycogen adds up to an astounding first week loss which is not likely to be repeated because the subsequent weeks have less food waste to process, a lower salt baseline consumption, and some muscle soreness as they overdo or wrongly do some of their exercises. And for women, you might catch your first week being the days right after your Aunt Flow visits.

earlnabby

Many people who start a weight loss program go through something like this: Your body sees what you are doing and drops excess fluid, frequently more than it should. It goes "Oopsie, I dropped too much, now I need to retain some more to get back to an optimal level. Finally "OK, I'm good".

For most who experience this, it takes about 3-6 weeks to cycle through. You drop a lot of weight, then you suddenly stop losing, then you start up again losing at a reasonable rate. All this time, you are losing fat.

I am in the "Oopsie" stage so I expect a week or two with minimal loss, then get back to normal. I am in week 3 of starting to lose.

lynn_glenmont

In part it is caused by a drop in average glycogen storage, and your body stores water with the glycogen. Because you're in a deficit, you are, on average, unable to top off your glycogen reserves, which normally go up and down as you eat and then do things during the periods between eating.

Evelyn_Gorfram

mkculs wrote: »

First, sodium isn't a goal--it's a max. Were you tracking it before you started here?

Yeah. I think of it as a goal as in "It is my goal not to exceed this amount."

And, unfortunately for the sake of this discussion, no, I was not tracking before I started tracking.

mkculs wrote: »

Usually that water weight is due in part to a decrease in the amount of sodium/processed foods you eat. For people who routinely ate out, ate a lot of processed foods, etc, to change to more eating at home, eating fewer processed foods, etc., it means a lot less sodium (among other things, like a lot less fat, too). I don't tend to eat much sodium -- never add salt to anything and don't eat out much--so I never saw that big first week or two change.

I eat out once in blue moon, and I generally try to keep processed foods to a minimum.

I love salt, and when the doc does blood tests my sodium levels always come back at the low end of the normal range, so I feel free to go hog wild with it. I salt almost everything (ever tried just a few salt crystals in your lemonade? - Mmm...), and pretzels are my favorite low-fat snack food, so it's hard to believe that there could be that big a change.

But, having thought back on it and checked it out, I was on a 1500 mg sodium/day boxed Mac-&-Cheese kick just before I started tracking, so that could be my seven pounds right there(!).

Orphia

It's not just the less water in your muscles and liver bound to the glycogen.

You also lose more weight in the first week because of less food and waste in your system.

lynn_glenmont

Orphia wrote: »

It's not just the less water in your muscles and liver bound to the glycogen.

You also lose more weight in the first week because of less food and waste in your system.

Well, some people actually consume greater mass of food by cutting back on energy-dense foods and filling up their plates with veggies that get their mass from water and fiber.

ETA: But definitely what you said is probably true in a lot of cases. I think the point I made accounts somewhat for something that puzzled me for a long time, which is the meme on MFP that some people have to wait for weeks after they start counting calories for "their bodies to adjust" (what??) and start seeing a change in their weight, whereas my instinct, based on my own experience, was that if you're not losing weight in the first week, you clearly are not in a deficit. I've always eaten a lot of whole, plant-based foods, so when I cut calories, I cut intake mass, and I've always seen a drop in the firs week. I think for some people, cutting calories is accompanied by a major shift in the kinds of foods they eat, and an actual increase in intake mass.

Orphia

lynn_glenmont wrote: »

Orphia wrote: »

It's not just the less water in your muscles and liver bound to the glycogen.

You also lose more weight in the first week because of less food and waste in your system.

Well, some people actually consume greater mass of food by cutting back on energy-dense foods and filling up their plates with veggies that get their mass from water and fiber.

ETA: But definitely what you said is probably true in a lot of cases. I think the point I made accounts somewhat for something that puzzled me for a long time, which is the meme on MFP that some people have to wait for weeks after they start counting calories for "their bodies to adjust" (what??) and start seeing a change in their weight, whereas my instinct, based on my own experience, was that if you're not losing weight in the first week, you clearly are not in a deficit. I've always eaten a lot of whole, plant-based foods, so when I cut calories, I cut intake mass, and I've always seen a drop in the firs week. I think for some people, cutting calories is accompanied by a major shift in the kinds of foods they eat, and an actual increase in intake mass.

I'm thinking of all the people on smoothie diets and LCHF.

And those doing moderation - just less volume of everything.

VUA21

Things that affect water retention:

Change in diet
Change in exercise
TOM
Stress
Salt
Sleep
Alcohol
Illness
Injury

Give yourself a month after incorporating a diet and/or exercise changes to get a better picture of your overall progress. So long as you're eating at a deficit, without going too severe (<1200 for women on average), just keep doing what you are doing.