Final answer:
The energy source for the body during rest and low-intensity workouts is lipids, particularly fats. Lipids are efficient energy stores due to their high caloric content compared to carbohydrates, and they also help in nutrient absorption and body insulation.
Step-by-step explanation:
The important source of energy for the body during rest and low-intensity workouts are lipids (fats). These organic substances are largely insoluble in water and include triglycerides, which are a major fuel source for the body at rest or during low-intensity activities. Lipids provide more than twice the energy per gram when compared to carbohydrates, making them an efficient form of energy storage. They are also crucial for the absorption and transport of fat-soluble vitamins like A, D, E, and K and serve as protection and insulation for the body's organs.
Proteins are primarily the building blocks of the body, contributing amino acids necessary for constructing our own proteins, whereas vitamins and minerals are essential for controlling bodily processes. Carbohydrates, specifically glucose, are the body's main source of immediate energy and are stored as glycogen or converted into fat if present in excess.