Final answer:
The thermic effect of food typically accounts for about 10% of total energy expenditure, with the human body converting most energy from food to thermal energy or storing it as fat, rather than using it for mechanical work.
Step-by-step explanation:
The thermic effect of food (TEF) or diet-induced thermogenesis refers to the energy expended by our bodies to digest, absorb, and assimilate the nutrients in our food. Generally, TEF accounts for approximately 10% of total energy expenditure. This percentage aligns with the understanding that human body efficiency in converting food into mechanical work is about 20-25%. Hence, the majority of energy from food is not used for mechanical work but is instead converted to thermal energy or stored as chemical energy in the form of body fat.
Human metabolism is efficient in converting chemical energy to mechanical work and heat, maintaining our body temperature in various environments. Most external work ultimately becomes heat, except for instances such as lifting masses, which is considered stored energy but eventually also converts to heat.
Even though the energy efficiency of our food intake and work output is relatively low, it coincides with other factors in human biology, including the ways our bodies store and utilize energy, which can lead to potential areas for improvement in terms of energy consumption and waste.