I am almost exactly 1kg lighter in the morning from the night before.
If you weigh yourself at night, it isn't as accurate because of different food weights and drinking.
I am on a 7000kj intake per day at the moment, if I have healthy food I consume about 2kg of food a day, if I have really bad food but the same kilojoules, the bad food would weigh about 800g to 1kg. So eating the good food would make you weigh more for a night time weigh in, but feeling full. Your body would process it all by the morning, and your weight not fluctuate as much for a morning weigh in. Drinking 500ml of water at dinner, then weighing in, will add 0.5kg to your weight, but that water will be gone by morning.
I think we lose about 0.5kg through moisture exhaled in our breath overnight and 0.5kg in our organs keeping us alive. My last food intake is at about 7.30pm and I usually have breakfast about 7.30am.
I think the main thing is to weigh yourself at regular intervals, weekly or fortnightly.
start date 14/1/2012