The scale proves it because I weigh less after a hard workout. Sweat is water, and losing water without replenishing it is not healthy. If you weight less after a workout, you're dehydrated, which means your muscles and nerves won't function as well, and you'll be slugglish and thirsty. A post-exercise loss of more than 2 percent of your body weight impairs the body's ability to run smoothly. A 5-percent loss is downright dangerous.
Excess fat is metabolized by aerobic exercise and eating less.
No magic, just dedication and discipline. Doing abdominal exercises shrinks the fat in my gut, just as doing leg lifts reduces the size of my thighs. And the tooth fairy really does leave money under your pillow. Spot reducing is a tall tale that just won't die. If you have a spare tire, doing abdomninal crunches will give you a gut as hard as steel-under the spare tire.