Fats

Fats are one of the main types of food your body needs to live and grow. Along with proteins and carbohydrates, fats are called a macronutrient. That means your body needs them in fairly large amounts. Fats are found in foods like butter, oil, nuts, cheese, meat, fish, and avocados.

Many people think fats are bad for you. The truth is more interesting. Your body needs fat to work. Fat helps you absorb certain vitamins, like A, D, E, and K. It cushions your organs and keeps you warm. It is also packed with energy. One gram of fat holds more than twice the energy of one gram of sugar or protein.

Fat is also a building material. Every cell in your body has a thin outer layer called a membrane, and that membrane is made mostly of fat. Your brain depends on fat too. Around 60 percent of the brain is fat, and the long wires that carry signals between brain cells are wrapped in a fatty coating called myelin.

Not all fats are the same. Scientists usually sort them into a few groups.

Unsaturated fats come mostly from plants and fish. They are liquid at room temperature, like olive oil or the oil inside a salmon. Most doctors agree these fats are good for your heart.

Saturated fats come mostly from animals. They are solid at room temperature, like butter or the white fat on a piece of steak. Eating a lot of saturated fat can raise a substance in your blood called cholesterol, which can clog the tubes that carry blood.

Trans fats are made in factories by changing liquid oils into solid ones. Doctors agree these are the worst kind. The United States banned most trans fats from food in 2018.

When you eat fat, your body does not use it right away. Your stomach and intestines break it apart. A green liquid called bile, made by your liver, helps mix the fat with water so your blood can carry it. Whatever your body does not need right now gets stored under your skin and around your organs. That stored fat is a backup energy supply your body can use later.

Fat is sometimes blamed for making people unhealthy. The real story is about balance. A small amount of the right fats, eaten with plenty of fruits, vegetables, and whole grains, helps your body do almost everything it needs to do.