Whenever I start a new diet and fitness I first; weigh myself, check my height, calculate my bmi, check my waist arm and thigh size, and record in my fitness journal. When I first started I had a bmi of 28.6 and most of my weight was fat not muscle, when building muscle your bmi may not decrease very much because muscle weighs more than fat: you'll see a difference even if that test doesn't. My greatest tool is my diet journal and calorie count. Seeing your actions and physical results on paper is a great motivation to stay on track for the goal you set.