Lipids are essential components of our diet because of their important contribution in energy, representing 9 kcal/g (or 37.7 kJ/g), and by some components relevant to the metabolism, such as essential fatty acids, fat soluble vitamins and sterols (cholesterol and phytosterols). Lipids (fats and oils) are an extensive range of organic molecules that activate several functions in organisms. Besides this, lipids have vital roles in human growth and development, along with prevention and treatment of various diseases. This book emphasizes on the importance of these molecules in the body and examines lipid metabolism in health and disease and also in plants.