Health is the general condition of a person in all aspects. It is also a level of functional and/or metabolic efficiency of an organism, often implicitly human. From Google dictionary: "The state of being free from illness or injury"
Nutrition is the provision, to cells and organisms, of the materials necessary (in the form of food) to support life. Many common health problems can be prevented or alleviated with a healthy diet.
Fitness comprises two related concepts: general fitness (a state of health and well-being) and specific fitness (a task-oriented definition based on the ability to perform specific aspects of sports or occupations). Fitness is generally achieved through exercise, correct nutrition and enough rest. It is an important part of life.