Remember when you first started drinking coffee? Just one cup would leave you feeling like you had enough energy to run around the block several times without wearing you out. But now, after drinking a cup (or pot) daily over time, just the idea of physically running anywhere is likely to make you want to lie down and take a nap. This may make you wonder why your coffee is no longer effective.According to something called chronopharmacology, which is the study of drugs and how they relate to your body’s natural rhythms, your body reacts to different drugs (like caffeine) based on where you are in any given 24 hour period. For instance, your body’s cortisol levels are at their peak first thing in the morning and although cortisol is normally associated with stress and weight gain, it also impacts your level of alertness. Therefore, by drinking caffeine when you’re already as alert as you can be, your coffee is probably not as effective as it would be if you drank it at other times when you’re not as naturally alert.Another reason coffee may no longer be effective for you is that you may have developed a caffeine tolerance. Essentially, this means that, by drinking coffee regularly over time, you’re no longer as susceptible to its effects. In fact, the only time you’ll likely notice the caffeine in this case is if you exceed your normal amount or quit drinking it for an extended length of time and then start again.To get the most out of your coffee then, you may want to save it for mid-morning, when your cortisol levels are starting to lower. Plus, it might also help to start cutting back, thereby reducing your tolerance levels and making smaller doses more effective.What are your thoughts about coffee? Is it effective or not?