Studies have shown that a fasted morning run may increase the utilization of fat as a fuel source, improve skeletal muscle function, enhance metabolism, and reduce appetite [1
]. Exercising in the fasted state may also reduce intake of food throughout the day, which can translate to weight loss [2
]. However, running in a fasted state may impair performance if you're doing maximal or near-maximal efforts since glycogen stores decrease overnight. In this case, eating something small before a morning run can be beneficial.