Why does weight fluctuate ?

[liffy99]

Nothing to do with FitBit as such, so perhaps a little off topic (I didn't know where else to post this question) but I just don't get it.

I've had my Charge HR for 2 weeks now and on every single day I have eaten significantly less than the 3000 KCals burned in a typical day (I'm, 6'4" and 103kg ish) - about a 1000 deficit each day.

Overall I have lost just over a kilo but when I think my weight should have gone down, it goes up ! An example . .

2 days ago I weighed in at 101.9kg. Since then I've consumed over 2000 KCals less than 'maintenance' level, and been to the loo as normal. This morning I weigh 102.3kg.

Why ? I am careful to log all my food (although I think FitBit over-counts my steps by assuming I'm walking 500 or so every night !

There's no doubt my diet has altered though - fewer carbs, very minimal alcohol, less snacking.

[WendyB]

It could be what you ate the day before. Was more Sodium involved?

But your weight will fluctuate all the time.

[WendyB]

Moved to the Manage Weight Forum where you will get more answers

[Malme84]

The calories in vs calories out is a general rule of thumb, but by no means something that can be used to highly predict weight changes. There are many factors that come into play, such as retaining fluids/being dehydrated, frequency of bowel movements, minor natural fluctuations in BMR, etc. etc.

[Dominique]

It is normal for your weight to fluctuate on a day to day basis, even if/when you are eating at maintenance. And if you are eating at a deficit in order to lose (mostly) fat (hopefully), your weight loss will not necessarily be linear. Often people expect an immediate change in their weight: my eating has been spot on today, I really worked my *ss off, so I should be rewarded for this on the scale tomorrow morning. And if this does not happen, they get discouraged. One solution to this problem (daily fluctuations / non-linearity of weight loss) is to link your Fitbit account to TrendWeight (free browser-based service). Here is what it looks like:

  

As you can see, individual daily weigh-ins (black spots) seem to go randomly up and down, but the red curve drawn by TrendWeight shows where your weight is actually trending (hence the name). So instead of focusing on what your weight happened to be this morning, just look at the red curve.

TrendWeight is especially handy if you have a Fitbit Aria scale (since your weigh-ins will be automatically synced to your account), but it also works if you manually update your weight in your account. TrendWeight also supports smartscales from Withings (since the Withings mobile app can be linked to the Fitbit app).

[sttatik]

Water weight. It all boils down to how much sodium you're ingesting. 

[liffy99]

So which was is the relationship ?
More sodium, more retention ?
Cheers

Stephen