Training for a marathon goes far beyond running. Building up your ability to run long distances — pushing your body to its limit — doesn't only consist of training runs, tracking your pace and finding the perfect running shoe. Our bodies need more. More fuel, to be exact. Let's start with the basics: What is fueling? It's exactly as the word 'fuel' would imply. We're essentially powering our bodies and supplying them with what they need to train for a marathon. Marathon fuel can range from a bagel for carbohydrates to an electrolyte drink for hydration, and much, much more in between. It looks a little different for everyone, but Meghann Featherstun, sports dietitian and seasoned marathon runner, has a few golden rules for fueling that all runners can keep in their back pocket (or running belt).