Just to ad my two cents worth, I've been working to get leaner for a little over a year now. I've always had a pretty regular workout regimen, but I found it curious that by bedtime I weighed as much as 8-10 lbs more than when I got up in the morning. Odd thing was that the leaner I got the less pronounced this effect was.

It took me a while to put two & two together, but I finally began to figure out that I was drinking a minimum of a gallon and a half of water a day (I know because I kept track). Water weighs 8 lbs/gal. so I was literally adding 8-12 lbs to my body weight each day in water. Muscle only holds so much water and then it's done, where fat cells will soak it up like a sponge and, like a sponge, expand as they do so.

I'm guessing that this is why you seem to get bigger as the day goes on, but then return to "normal" during the night when your body is drying out...so to speak.

YMMV