Glucose. All types of food can be digested, or broken down, into simple sugars. And, the simplest sugar that your body can use for energy is glucose.
For us here on Earth, the prime source of energy is the Sun.
The source of energy for plants is sunlight.
In most food webs the Sun is the ultimate source of energy. Some food webs start with chemotrophs and in those cases the source of the energy are chemicals often from underwater volcanoes.
from food
chemical to machanical energy
Yes fats are the most calorific energy source.
No Food under normal circumstances is a renewable source of energy. Food is the result of plants getting energy from the sun and converting this energy into storage. the plants can the be eaten and the energy used. The plant however puts out seed and grows again renewing itself as a source of energy.
the source for all enery is sunlight
plants
Food stores fat. Fat is an energy source of the body.
carbohydrates
The main source of energy is from the sun.