None of that {censored} matters.
Calories are energy. Unused energy is converted to mass. Go to a nutritionist and have them determine what your maintenance Calorie rate is. Eat less than that if you want to lose weight, eat more than that if you want to gain weight.
Activity can modify the amount of Calories you need. If you're a crazy body builder you might be eating upwards of 10,000 Cal/day., but the nutritionist will help you figure this out.
Within that limit, eat whatever you want, though I suggest staying the hell away from most anything artificial. Nutrasweet, margarine, low fat/fat free stuff, etc.