Weight difference during the same day
 

This morning when I woke up and weighed myself, I was at 148. After a couple of meals (oatmeal.. tuna... milk... and water..) and a light workout, my scale says 161. How on earth can there be such a big difference in one day! And I know that tomorrow when I wake up, I'll be right back at 148.

I've noticed before that I weigh like 5-6 pounds more in the afternoon than when I first get up and never thought anything of it, but 13 pounds????? Where does this all come from and where does it go at night while I sleep??

You weren't hung over/massively dehydrated in the morning?
Wearing different clothes?
Using different scales?
Errm... different gravity in the area?

Nope, I don't drink for one thing..
Same clothes - just boxers.
Same scale.
Gravity? Maybe that's it - lol

Actually your body weight can vary incredibly during the day.

Water, food ... adds up quickly :)

The best way to go is simply weigh yourself at the exact same time every morning.

I would just add:
The best way to go is simply weigh yourself at the exact same time first thing every morning.

You lose a lot of mass overnight just burning energy to maintain your body temperature (lost via heat) and through sweat. And of course during that 3 am run to the bathroom b/c of that night cap.

You do lose a few pounds overnight and gain some during the day. I personally never fluctuate more than like 5 pounds during a day, unless my true weight is making a shift.

I don't know my wieght in lbs ..
But i'm about 66.5kg in the morning when i get up ..
After the morning breakfast im about 67 .. and in the afternoon after the run and ALOT of food during the day .. im back at about 69 :)

1kg = 2.2lbs, so Subform you're going 146lb to 152 (ie 6lb change). I think that's fairly typical, but a1t3r3g0 and his 13lbs does seem like quite a lot. Has it happened again since?

You must have been very dehydrated when you first weighed yourself.

Most of your body weight is in water... that's how boxers/wrestlers are able to drop huge amounts of weight quickly to "make weight" in their class, then put it back on within 24 hours.

Even then, a 13 pound difference is huge... did you do tons of exercise the day before? Maybe you were still dehydrated from it.

If you're Lance Armstrong, yeah-in one stage he lost exactly that-13 pounds. Extreme situation though.

Probably caused by a problem with the scale. I have a decent scale ($60 or so) and every once in awhile it throws out some number thats like 10 lbs off. I step off and immediately back on and then it gives me an accurate measurement. I'd be surprised if you had that much of a true weight swing in 1 day