Eating well under your recommended levels can also be a reason for not losing weight.
The body needs a certain amount of calories to simply carry out its daily activities such as breathing, digesting, and keeping up with your physical activities. Every person has an amount of calories required each day to maintain their current weight. People who gain weight are usually eating more than they need to and people who lose weight usually eat less than they need. Let us assume that your recommended daily intake for maintenance is 2000 calories. If you would eat only 1000 calories a day you would essentially be slowing your metabolism down as opposed to the intended goal of speeding it up. The reason is because the body is not getting enough fuel to survive and as a result cant afford to expend energy by burning fat, so instead it saves up as much as it can which leads to stagnant weight loss. In extreme cases the body even begins to feed on muscle tissue to survive, so people may even see the numbers on the scale drop but it is obviously not the number they are looking for.
The correct thing to do in order to lose weight in a safe and effective way is to eat only about 500 calories less than the RDI (recommended Daily Intake). I should also mention that the RDI takes in to account your activity level, so if you do exercise then depending on how often and how rigorous you work the more calories you must consume to maintain your weight. There are calculators that you can find online that can tell you how many calories you should consume on a daily basis.
This particular one will ask you for your age, gender, and activity level. Once you have that info put in it will tell you how many calories you should eat to maintain your current weight and also how many calories you should eat to lose weight. I dont know how accurate it is, but it is certainly a good place to start. Once you know basically how many calories you need, you can then pay attention to your results and then tweak the amounts accordingly. If you are not losing then you know you should be eating a little less. If you are losing then you know you got it right and so on.
Another thing worth mentioning, and with this I will conclude, you should pay closer attention to your waist line rather than paying attention to the scale. The scale tells you how much you weigh, but it does not single out your fat. It includes bone density, muscle mass, water, and finally fat, so when you see the number dropping you cant be certain what it is.