I'm on a 4000 calorie a day diet and went from 220 of fat to 180lbs of muscle in 6 months. I went from a 40" to a 32" waist(loose). Thing is I'm 5 foot 11 male and doing 2-3 hours of cardio and lifting a day. My 110lb 5'4 girlfriend who is mostly abs and does yoga everyday only needs 1200 or so lean vegetarian calories to stay in shape. So not only are people different sexes and sizes they all have different fitness goals.