Answer:
Energy balance.
Step-by-step explanation:
Energy balance is the relation between the energy you intake and the energy you output. This concept is thermodynamic's law which says that energy is not created or destroyed, it's just transformed. Translated to healthy context, energy balance dictates that weight is lost, gained or maintained, there are only these tree possibilities.
Moreover, the purpose of energy balance is to consume the needed energy only, not much than that, because the excess is transformed to fat, which is unhealthy weight gain. To have a proper energy balance, people must to record how much calories they are consuming to then exercise