Weight loss is among the top New Year's resolutions on everyone's list. We usually think of burning fat when it comes to losing weight. A healthy diet and exercise are key essentials to dropping the pounds, but what happens to those fat-storing cells?

In SciShow's video, "Do Fat Cells Ever Really Go Away?" host Michael Aranda explains the fat in our body is actually a connective tissue made up of cells called adipocytes, or fat cells. The skinny on fat cells is they never really go away — they can grow and shrink, depending on whether we're gaining or losing weight, which is a good thing. This tissue plays an important role in our anatomy.

Fat gives our body structure, cushions our organs, and keeps us insulated to help regulate our body temperature. However, its primary function is to store energy. So when we eat, sugars in our food are the first form of energy to be used.

Read: When You Lose Weight, Where Does It Go?

When we're not eating, our body needs a way to access energy from somewhere so we can still function. Like any other cell in the body, fat cells have a nucleus and organelles, but they're specialized so that 90 percent of each cell is basically just a pouch for fat storage, and the fat storage unit that our body uses is called a triglyceride. It's made up of three fatty acid chains, and a molecule of glycerol — a kind of alcohol that serves as a backbone for the fatty acids to attach to. The bonds in fatty acids contain a lot of chemical energy, so it's in this form that fat sits around in our adipocytes.

Triglycerides are broken down into their component fatty acids with the help of a protein known as LPL, or lipoprotein lipase, when they're needed for energy. Those fatty acids can then pass through the membrane of the fat cell where they're dispatched to be metabolized elsewhere so their energy can be unleashed. In the process, the fat cells shrink, but if more triglycerides get stored than get used up, that's what causes adipocytes to grow, and larger fat cells means more adipose tissue.

To lose weight, enough energy is needed to break down the triglyceride stores into fatty acids that can further be used as energy, shrinking the fat cells. This does take a lot of work, and even if we do shed the pounds, it's easy to gain back since it requires less energy to store excess fat than to burn it.

Sedentary lives can lead to fat cells sitting unused, and forgotten.

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