Fluid retention. A few alcoholic drinks, sodium-rich fast-foods or take-out, and late-nights contribute to the bloat. The bigger you become, the greater the %age of water weight fluctuation will be noticed. Its all relative to the change of life-style we all experience on weekends and holidays. I put on around 3-4 #s a weekend, and its gone by tuesday night/wednesday morning. Its not a big deal. Unless your going to be moving alot of weight, or planning on doing alot of aerobics, dont let it spiral out of control for weeks at a time.