How Young Do You Want to Feel? Your calendar age is just a number. What really matters is how you look, how you feel and how much energy you bring to your day. Your biological age- your Bio-Age- is what counts. You can't make yourself younger chronologically (be honest now, do you really want to be 15 again?) but you can change your Bio-Age. We all know people who look and perform like someone 10 years older than the age on their birth certificate...