This TedX video by physicist Ruben Meerman asks the question "When we loose weight (moreover fat) where does it go?"
Its very interesting and gives the watcher a strong sense of how weight loss actually works.
There are several little props and chemical reaction that help illustrate the process.
"10 kg of fat becomes 8.4 kg of invisible gas (C02) that you breath out. That's amazing. Every time you are doing some exercise and your breathing rate goes up you're losing more weight than when you're sitting down and not breathing as rapidly."
It turns out accelerated breathing has much to do with weight loss.
I do love the simplicity of how he states the formula for losing weight: "Eat less and move more".