Final answer:
The thermic effect, which is part of the total energy expenditure, accounts for about 10% of total energy intake. The remainder of the energy consumed either maintains body temperature, supports biological functions, or is stored as fat.
Step-by-step explanation:
The thermic effect of food (also known as diet-induced thermogenesis) is the increase in energy expenditure above the basal fasting level divided by the caloric content of the food ingested and is a component of the total energy expenditure. According to various studies, the thermic effect accounts for approximately 10% of total energy intake. This is because human metabolism is only about 20-25% efficient at converting chemical energy from food into mechanical work (like movement), while the remainder is lost as heat or stored as chemical energy in fat.
Some examples provided discuss different aspects of human energy use. For instance, in doing work, the efficiency can be in the neighborhood of 25%, requiring us to consume about four times the energy we expend in work. However, this consumed energy does more than just enable work; it maintains our body temperature and supports all our biological functions. Additionally, there is food waste to consider, which complicates calculations for energy intake and output. In the U.S., for every 1 kilocalorie consumed, 1.8 kilocalories of food value is produced, notably indicating the scale of waste in the food system.
When considering workouts and the efficiency of an athlete, it's indicated that a well-conditioned athlete might operate at about a 20% efficiency rate, meaning even athletes convert a significant portion of their caloric intake into thermal energy rather than work output. Overconsumption of calories beyond what the body expends in work and heat production can lead to storage of excess energy as body fat. Understanding the ratios and percentages of energy use can help better manage energy intake and maintain a balanced diet, particularly in relation to caloric consumption and exercise.