In his book Eat Fat, Get Thin, Mark Hyman, MD, explains why fat is not the enemy so many people think this necessary nutrient is. “Fats function to promote health, help with effortless weight loss, prevent heart disease and cancer, improve your mood and brain function, and help to prevent and even reverse dementia in its early stages,” Hyman says.

Many people believe that if we eat less fat, we’ll consume fewer calories and lose weight. This sounds like a winning formula, but the equation doesn’t necessarily yield the desired result.

“The theory that all calories have the same impact on your weight and metabolism remains one of the most persistent nutrition myths that keep us fat and sick,” Hyman says in a recent blog post. “All calories are the same in a laboratory when you burn them in a vacuum. However, your body is not a laboratory. It is an intricate, interconnected organism that simultaneously juggles thousands of duties.”

In general, the body uses fats as a source of energy and heat. But this nutrient also insulates and protects vital organs of the body. In addition, fats help to break down proteins and trigger other chemical reactions in the body, such as helping with immune function and controlling growth and reproductive processes.

Hyman says the best dietary fats can help us get lean and charge up our bodies’ batteries. His particular favorites? Avocado and coconut butter.