All of you autist oversimplify a multivaried equation. Fat is the result of multiple variables that are weighted differently depending on genetic makeup.
Food intake matters - you're right, but it isn't all about food
Exercise matters - you're right, but it is not JUST about exercise. Do you run 8 miles then eat a melted tub of butter with Aunt Jemima mixed in?
Genetics matter - we're all born with varying amounts of fat cells. We control how much these fat cells balloon up (or shrink down) but we cannot control the amount of fat cells we have.
This is a multivaried equation and the individual variables could be weighted differently depending on the individual. This is why tracking what you eat is imperative. This is usually the fist step in any diet/exercise program that is worth a shit. This is also why body scans are important to measure progress. Weight alone means little and can actually derail a person from turning his or her life around. Lean body mass is what you need to find and a scale doesn't find this. Styku scan (or other types of scans) are good - not perfect, some margin of error - and a hell of a lot better than just standing on the scale.
Quit oversimplifying a complex problem and fucking run from anyone that give you a generic, one - fits - all solution for your fitness.