1. Energy storage: Lipids, particularly triglycerides, are the most efficient form of energy storage in the body. They provide more than twice the energy per gram compared to carbohydrates or proteins. This energy is used for various bodily functions, including muscle contraction, brain activity, and maintaining body temperature.

2. Structural components: Lipids form essential components of cell membranes, which act as barriers, controlling what enters and exits the cell. They also contribute to the structure of myelin sheaths that insulate nerve cells, allowing for efficient nerve signal transmission.

While these are the two main functions, lipids also play many other important roles in the body, including:

* Hormone production: Steroid hormones like testosterone and estrogen are derived from cholesterol, a type of lipid.

* Insulation: Fat deposits under the skin act as insulation, helping to maintain body temperature.

* Protection: Fat pads around organs provide cushioning and protection against impact.

* Vitamin absorption: Fat-soluble vitamins like A, D, E, and K require lipids for absorption from the digestive system.

Therefore, lipids are essential for maintaining health and proper functioning of the human body.