What I would really like to emphasize right now is that people should really stay away from weight scales. NO SCALES! There are exceptions to this rule of course, but everyone should be mindful of why the scale can bring the worst out of your fitness program. Weight scales don't take into consideration what kind* of weight is being gained or lost. Often times, it gets people obsessed with losing or gaining pounds rather than losing fat and building healthy-lean muscle tissue. We want immediate results sometimes will do anything to get it. Please don't do that. The long way is the fast way.
When it is okay to use the weight scale? It's okay to use the scale to plug into a real body composition analysis methods such as hydrostatic weighing or Near-infrared reactance. Calculating body composition is very helpful because with can one see whether our program is forcing our bodies to catabolize muscle tissue which is necessary for sustaining longevity and higher metabolic rates and useful for true fat loss.
Another way to use the weight scale is to monitor weight loss in a more healthy way. Here is really comes down to having proper goals. If your goals are to lose as much weight as possible in the shortest time, than you might be setting yourself up for failure. If your goal is to find your metabolic set-point, in order to calculate how many calories should be consumed daily, than that would be helpful. To do this you'll of course need to count calories. Find the number of calories which allows you to maintain the same weight over time and you've just found for metabolic set point. As long as your macro nutrient content is healthy then you know it's safe to drop 2 or 3 hundred Calories from your daily diet without hindering your body's metabolism due to muscle loss. Of course the more overweight a person is the more fat they can lose without tapping into too much muscle tissue, but most of us the maximum fat loss per week should be between half of a pound and two pounds. If more weight is being lost in a week than that, it's very likely lean-muscle tissue is being lost which can cause long-term weight loss difficulties.
Finally we should discus DMI (Body Mass Index). BMI is calculated by a ratio of weight to height. This also does not take into consideration lean-muscle tissue or actually body fat composition. Using methods like these are like eating steak with a spoon. It kind of works, but something is just not right.
I have a friend who was a high school foot ball player. He was in excellent shape, carrying tons of muscle and was fairly tone. He saw a doctor for a routine check-up and according to his BMI he was overweight. The doctor recommended he lose 15 or 20 pounds. What an idiot! Clearly my friend was in much better shape than the majority of people with a "healthy" BMI. BMI is almost worthless. If anything, it's best to just look into a mirror and see results for what they really are. It may also help to keep a picture log in order to track results from week to week. You could create fun animations!
So is important to keep in mind that just losing lots of pounds is not the best way to go. Losing tons of weight quickly with low Calorie diets isn't always healthy nor does it tend to bring out long-lasting healthy lifestyle changes.