Final answer:
The majority of calories needed by the body are provided by the basal metabolic rate (BMR), which supports basic bodily functions and represents around 75% of daily caloric usage. Daily caloric needs range from 1500 to 2000 calories on average. Both the metabolism of various nutrients and studies on specific populations provide insight into energy needs.
Step-by-step explanation:
The majority of calories needed for the human body primarily comes from the energy expended to sustain basic life functions, which is defined by the basal metabolic rate (BMR). About 75% of the calories we need are dedicated to metabolic processes such as the functioning of the liver, spleen, and brain. BMR is influenced by several factors, including age, gender, body weight, and muscle mass. As a rule, proteins require more energy to metabolize compared to carbohydrates and fats.
Daily caloric needs average between 1500 to 2000 calories for normal activities without considering additional exercise, which would increase the requirement. Notably, studies such as the one conducted by Carla Prado's team at University of Alberta help improve our understanding of energy expenditures in various conditions, like postpartum recovery in women, via methods like whole-body calorimetry. Therefore, the quality and quantity of food intake alongside the metabolic rate determine overall health and energy storage or depletion in the body.