It's a great debate — eating fat makes you fat, too. But then studies show we need fat in our diet in order to be healthy and even lose weight. So what’s the deal? In a new video from SciShow, host Hank Green delves into the complicated dietary science of all things fat.

Hank begins by explaining what fats are — "molecules that organisms use to store energy… so they can be converted into lots and lots of energy for running an organism, whether it’s a seed growing into a plant or a neuron firing in your brain." Fat is also energy dense, boasting more than twice the energy of protein or carbohydrates per gram. And like everything else we eat, it's made up of chemicals comprised of long-chain carbon atoms, which can be broken down by the body into usable energy.

"The energy density of fat combined with the fact people who ate high-fat diets tended to be less healthy was the original cause of the anti-fat craze that started in the 60s and continues, at least to some extent, today," Green said. "But it turns out that fats are not inherently bad for you. Indeed, they are an absolutely necessary part of the diet."

But this doesn't apply to every type of fat; there's saturated fat, unsaturated fat, hydrogenated fat, polyunsaturated fat, trans fat, and omega-3 fatty acids. The differences come down to the fat's particular carbon chain — Green maps each one out in the video in order to explain the chemistry behind the carbon bonds.

Some key takeaways: Trans fat is a no-go, and you should probably be getting a little bit of both poly- and mono-unsaturated fats. As far as omega-3 fatty acids, they're one of two essential compounds, the other being omega-6 fatty acids. Essential compounds refer to the necessary chemicals the body needs to make on their own, so we need a healthy ratio of omega-3s and omega-6s to survive. These can be found in seeds, nuts, some spices, and oily fish. Bonus: Medical Daily makes seafood shopping easy with this handy nutrition guide.

The bottom line, Green said, we need fat to survive. It’s good for you, so long as you eat it in the correct quantities.