In a nutshell, fitness is defined as the state of being physically fit and healthy. ... So I equate fitness with both the mental and physical states and working towards having a body that can function well in everyday life.This article provides details on what physical fitness is, what it means to be fit, and the five main components of physical fitness.Get fit! Being fit does not necessarily mean having six pack abs, bulging biceps or that perfect bubble butt. Fitness means different things to .