Your weight (or more properly mass) is probably something that you think about a lot if you are trying to slim. It is easy to get emotionally invested in that magic number on the scales but how relevant is it really? I say not very.
"Overweight" in the conventional sense means that your proportion of body fat is too high meaning that you look visibly fat. In the scientific sense "Overweight" means that your body mass index (BMI) is above a certain number. BMI though a useful indicator when it comes to monitoring populations and for broad analysis is pretty useless when it comes to individuals as it makes no distinction between muscle (or lean mass) and body fat. I don't set any store by it, neither should you.
Conventional wisdom states that if you "eat less" you'll "lose weight" and this is largely true, however, while dieting by caloric deficit alone will most assuredly reduce your overall mass it won't necessarily reduce your percentage of body fat. You might be lighter on the scales but you won't be healthier and you won't be (much) thinner.
A close friend of mine recently lost 8kg in two weeks by going on a crash diet that she had sworn by in her college days twenty years ago. I didn't think it was a good idea but she believed it would help which is half the battle when it comes to sticking to a diet. She did well in sticking to the (rather weird) low calorie programme and lost a lot of "weight" but she didn't really look any slimmer.
The reason being, she lost lean mass and not body fat. Your lean mass or muscle is supported by protein. You need dietary protein to feed your muscle and prevent your body breaking it down for fuel. You also need to exercise to tell your body that you are still using it and that you need it.
The formula to improve body composition is simple and certainly no secret. You need to consume 1(min) to 2(max) grams of protein per day per kilo of lean body weight. Cut out simple sugars and excess carbohydrates and consume enough healthy fats.
Moderate Caloric deficit, a sensible split of macro-nutrients based on your current body composition and a mixture of types of exercise (for example PT sessions with me and low intensity exercise like walking or bike riding) will mean you'll lose body fat, protect your lean mass and feel great no matter what the number on the scales is.
Weight has nothing to do with it....