I never understood why there's even a scale at the gym. The only time you should be weighing yourself is in the morning, first thing out of bed with no clothes on. You just woke up from a 6-8 hour fasted state and that's when your body is empty of food and at its "true" weight. If you weigh yourself at any other time you are going to have a fluctuation +/- 5lbs of undigested food in your stomach. If you're an advanced lifter or competitor and weighing in day to day for comparison, you definitely can't have that fluctuation sigma. Weigh yourself naked unless you know exactly the weight of your clothes. Jeans and sweats do not weight the same.