Nutrition, is the supply of food required to stay alive. It is the study of nutrients in food, how the body uses nutrients, and the relationship between diet, health and disease. Diet plays an important role in a person’s health, appearance, energy, athletic performance, and response to exercise, as well as overall well-being. Personal trainers are, however, encouraged to help educate their clients with respect to making healthy food choices. Some nutrients are required in large quantities (macronutrients) and some are required is small quantities (micronutrients).