Lipids are fundamental to life itself. Without fat and its components, not only would the very cells within an organism fail, the individual working components within cells would cease to be. In other words, while a low-fat diet might have some value for some people and for certain conditions, a no-fat diet would be fatal.
When discussing healthful fats, it is more accurate to refer to the component fatty acids, the chains of carbon atoms that differ in both length and degree of saturation. (Saturation refers to the number of hydrogen atoms linked to each interconnected carbon in the chain.) It’s the unique fatty acid profile that gives individual fats their characteristics and functionalities.