We all know our metabolism slows as we age. But did you know that a lot of the decisions you make throughout the day may actually be helping to slow it down? In fact, you are likely messing with your metabolism and not even know it. These mistakes will slow down your metabolism when you need to be revving it up. But we are here to help. Below are a list of common mistakes many of us make as we age and look to lose weight. If you can avoid these, chances are you can keep your fat-burning engine in tact.