Bananas are high, bananas: 91 calories/100 grams; apples: 52 calories/100 grams.

And this energy comes mainly from food. Nutrients contained in animal and plant foods can be categorized into five major groups:carbohydrates, lipids, proteins, minerals and vitamins, plus water is six major groups. Among them, carbohydrates, fats and proteins can be oxidized in the body to release energy. The three are collectively known as "energy nutrients" or "heat source quality".

The pathway of calorie consumption has three main parts, the first part is the basal metabolic rate, accounting for about 65 to 70% of the body's total calorie consumption, the second part of the physical activity, accounting for about 15 to 30% of the total calorie consumption, and the third part of the thermal effect of food, accounting for a minimum of about 10%, which has been fixed in proportion to the ratio of these three roughly.

The relationship between heat and internal energy is analogous to the relationship between work done and mechanical energy. Heat is a measure of the change in internal energy of an object. If thermal equilibrium has not been reached between two regions, then heat is transferred from the warmer part of their center to the cooler part.