There is a big difference between losing weight and changing your body composition. Losing weight is purely Newtonian (do I have more or less mass on my body). However, weight does not equate to looks and performance. One of the issues with chasing a number on a scale is that it can give you a false understanding of how your body is actually changing. For example, you can really manipulate your body weight by changing salt, carb and water intake. So, by cutting out carbs and drinking less water you can trick yourself into thinking you are making the progress you want by reducing your body weight. However, cutting out carbs and water really reduces your energy levels and performance levels in the weight room. A vicious cycle can be started if this occurs, because you see weight loss, you want to keep it going, you begin to lose energy (start swapping out your resistance training for long slow cardio) and next thing you know, you are at the desired body weight but with a potentially worse body composition. The number you see on the scale is only a small part of the big picture when it comes to achieving your goal body composition.