My weight has fluctuated as much as 12lbs in a day simply due to water retention. For example, I'll wake up at 205, but got to bed at 215. Make sure you are weighing yourself first thing in the morning before meal/drink. Also, an anti-estrogen like arimidex, letrozole or aromasin will help keep the water retention to a minimum (as would an androgen like tren, masteron or proviron).