Both energy gels and energy bars are foods that contain a high calorie content and quickly replenish the body's energy and mineral needs during heavy exercise. Energy gels are gel-like liquids and energy bars are chunky solids. Many people like to take a pack or two with them on their runs. Energy gels are very high in calories, and if the usual intensity of a single training session does not reach a certain level, there is actually no need to supplement.

Energy gels don't make runners run faster and farther, its just supplementing the calories consumed. Professional marathoners rarely need energy gels during their runs, and generally just supplement with water or electrolytes.