ABSTRACT
In 1841, the German physician Julius Robert von Mayer (1814-1878) enunciated the “rst law of thermodynamics,” saying that “energy can neither be created nor destroyed.” These days, the law of thermodynamics is one of the most fundamental basics of energy metabolism control. When translated to the regulation of body weight, the law means that the energy (calories) consumed must match the body’s energy (caloric) demand to sustain a stable body weight over time. Any prolonged deviation from this equilibrium will inevitably result in either weight gain (in case energy intake exceeds energy expenditure) or weight loss (in case energy expenditure exceeds energy intake). Accordingly, to maintain a stable body weight over time, energy intake constantly needs to be adjusted for changing energy demands. Based on the constant changes in this demand, the adjustment of energy intake must be achieved through the (shortterm) regulation of caloric intake (e.g., through regulation of the meal size and/or the meal frequency) and must take into account (long-term) information about the energy stored as fat in the body.
