Final answer:
The body breaks down food into glucose and other substances during digestion, which are used immediately for energy or stored for future use. When energy intake exceeds immediate needs, the body stores the excess as glycogen or fat. Our bodies are constantly converting and balancing energy from food into work, heat, or stored energy.
Step-by-step explanation:
The body obtains energy from food through a process that begins the moment we consume food. The digestion process breaks down carbohydrates, fats, and proteins into their constituent substances such as sugars, amino acids, and fatty acids, some of which, like glucose, are critical for immediate energy use, especially by the brain.
During the absorptive state, the digested nutrients are absorbed through the intestine and transported via the bloodstream to various cells for immediate use or storage. Excess carbohydrates are converted into and stored as glycogen in the liver and muscle tissues, or transformed into fat and stored in adipose tissue when glycogen stores are full.
Our body systematically performs energy conversion. The chemical energy from the food we eat is converted into work, thermal energy, and stored in fat tissues. When we engage in activities, we convert this stored energy back into work or heat, maintaining a balance between energy intake and expenditure.
During times of fasting or when immediate glucose is not available, the body utilizes these energy stores to maintain homeostasis and supply the organs with the necessary energy. This is vital as some organs, like the brain, require a constant energy supply.