Losing and Controlling Weight
The Energy Balance
The energy balance describes the balance between energy consumed and energy used. Energy can be defined as the system’s ability to perform a job – it can be in the form of light, chemical, mechanical or electrical energy or in the form of warmth. The first law of thermodynamics says that energy can neither be created nor destroyed; it can only be converted from one form to another. The chemical form of energy in food consumed by an individual is intended for the performance of different tasks (the synthesis of macromolecules, muscle contractions or in the form of electricity for maintaining numerous ionic gradients across cell membranes). The energy balance is described by the following equation:
Energy intake = energy expended + ∆ energy stored
This means that if energy stored in the body remains unchanged (∆ energy stored= 0), energy expended should equal energy intake. We can then say that an individual is in energy balance.
If energy intake and energy expended are not in balance, a change will inevitably take place in the energy stored. A negative energy balance leads to a loss of bodily reserves and thus weight, while a positive energy balance results in an increase of bodily reserves and thus also weight.