*Geek Box: Homeostatic and Hedonic Regulation of Appetite
When we discuss concepts like satiation and satiety, it is important to note that these concepts are part of the overall framework of human appetite regulation. Appetite may be considered the set of processes that influence food intake; hunger reflects the motivational drive to eat food. As such, there are distinct processes that influence both appetite and hunger; these can be distinguished as homeostatic and hedonic processes.
Homeostatic processes reflect the control over how much food is eaten, quantitatively [i.e., energy intake]. Homeostatic regulation of energy intake is a balance between orexigenic [i.e., appetite promoting] and anorexigenic [i.e., appetite suppressing] pathways in the brain, which influence both acute and long-term energy availability [both in diet and in stored energy, i.e., body fat].
In theory, eating behaviour would be governed solely by our energy requirements, where we would only consume as much energy as required to meet energy expenditure demands. However, humans evolved in natural environments with unpredictable food availability, and energy intake is not solely governed by homeostasis, with food-related motivation-reward processes and environmental factors influencing how much is eaten.
The motivation-reward influence on eating is known as the hedonic process, driven by two sides to our brain reward systems: ‘wanting’, driven by dopamine, and ‘liking’, driven by opioids and cannabinoids. ‘Wanting’ triggers the intense motivational urge for the food reward, while the opioid-driven ‘liking’ response conveys the hedonic properties of food [often energy-dense, sugar, fat, and salt-rich foods].
The main point to take home is that homeostatic regulation of appetite is not tightly controlled, and hedonic motivation to eat is influenced by social, environmental, and cognitive factors, which can promote consuming energy in excess of homeostatic needs.