It does work. It couldn't not work. Each day of your life, you choose to do one of three things:

1. Consume more calories than your body will need to function

2. Consume as many calories as your body will need to function

3. Consume fewer calories than your body will need to function

When you consume more energy than you require, your body stores the remainder as fat. When you consume less energy than is required, your body converts your fat into usable energy.

Now obviously, this is an over-simplified explanation of nutrition. What you eat, when you eat it, how efficiently your body converts food to energy, and other factors will determine the little details. But the explanation I've provided is not nearly as over-simplified as "it just doesn't work."

To make a comparison, it would be like suggesting that the financial advice "earn more money than you spend" just doesn't work as a method of saving money, on the grounds that some % of Americans who try to save money end up in credit card debt.