> So while you may feel that coffee is giving you more energy, it’s simply telling your body that your energy reserves are good to go even after they’re long gone.

I'm not an expert by any means, but this isn't quite what I learned in my undergraduate course on metabolic biochemistry. Caffeine simply encourages you to burn more energy by the mechanisms outlined by the author. However, you cannot burn energy reserves after they are gone. Where would the energy come from? You have carbohydrate reserves and you have fat reserves. Carbohydrates will go first, and once depleted caffeine will cause you to burn more fat than you normally would. The effect is somewhere around 10% for average consumption levels. When you have burned all of the usable carbohydrates and fat in your body, you start burning protein. That is called ketogenesis. It results in muscle breakdown, and the ketones produced are one of the reasons crack addicts smell kind of funny. Caffeine will not induce ketogenesis unless you are drinking way too much and not eating nearly enough. Note that there aren't super sharp transitions from carbs to fat and from fat to protein.