GLOSSARY

Metabolic Efficiency relates a useful output or retained energy to an energy input under a stated definition. Metabolic, storage and mechanical efficiency are different applications and should not be treated as one universal property.

The body stores substantial energy in adipose triglyceride, more limited carbohydrate as glycogen, and energy in functional proteins that can also be broken down. Protein tissue is not a dedicated expendable fuel tank. Glycogen is stored with water, so its depletion and restoration can shift body mass rapidly. Mobilizing a fuel does not prove that it is oxidized or that total fat stores are falling. Net storage over time depends on both entry into and removal from the relevant pool.

Energy and nutrients are distributed among oxidation, synthesis and storage through interacting pathways. The composition of weight gained or lost depends on more than the numerical calorie gap. Protein, training and initial body composition are relevant, and wet tissue contains variable water. The energy content of a tissue is not identical to the dietary energy required to build it. A single constant energy-per-kilogram rule therefore cannot precisely predict all future body-mass changes or distinguish muscle from other lean components.

Over a defined interval, a difference between metabolizable energy intake and energy expenditure changes stored body energy. This principle does not imply that daily scale weight directly reveals energy balance. Water, glycogen and gut contents also contribute to body mass. Intake and expenditure influence each other through behavior and physiology, so projecting the same daily deficit indefinitely creates unrealistic predictions. Interpret the energy equation together with its timescale and the composition of the tissues changing.