Three kinds of fat

Food contains three kinds of fats: triglycerides, phospholipids, and sterols.
Here’s how they differ:

• Triglycerides: You use these fats to make adipose tissue and burn for energy.
• Phospholipids: Phospholipids are hybrids — part lipid, part phosphate (a molecule made with the mineral phosphorus) — that act as tiny rowboats, ferrying hormones and fat-soluble vitamins A, D, E, and K through your blood and back and forth in the watery fluid that flows across cell membranes. (By the way, the official name for fluid around cells is extracellular fluid. See why I just called it watery fluid?)
• Sterols (steroid alcohols): These are fat and alcohol compounds with no calories. Vitamin D is a sterol. So is the sex hormone testosterone. And so is cholesterol, the base on which your body builds hormones and vitamins.