Food intake is regulated by two complementary pathways in the body and brain that signal us to consume food: the homeostatic and hedonic pathways. The homeostatic pathway controls energy balance by increasing signaling to motivate us to eat following the depletion of energy stores. Hedonic or reward-based regulation can override the homeostatic pathway and enhance signals in craving and consumption of HPFs during periods of relative energy abundance (Lutter & Nestler, 2009).

Hormones are chemical signaling molecules secreted directly into the bloodstream by glands and carried in the circulation to target tissues and organs where they can bind to specific cell sites known as receptors. By binding to receptors, hormones elicit various biological responses in the tissues containing the receptors (Stárka & Dušková, 2020).

Hosts in biology are larger organisms that harbor smaller organisms inside or on their bodies (Casadevall & Pirofski, 2015). In this course, we commonly use this term to refer to animals used in scientific research studies or humans, with the smaller organisms being millions of gut microbes.

The HPA (hypothalamic-pituitary-adrenal) axis dysbiosis-neuroinflammatory cycle is a proposed mechanism of how chronic stress and an imbalanced gut microbiota can contribute to the development and perpetuation of neuroinflammation and mental disorders.

Hunger hormones stimulate appetite and the desire to eat. Ghrelin is a notable example of a hunger hormone.

Hyper-palatable foods (HPFs) are food categories distinguished by their highly pleasurable taste and sensory appeal, attributed to their elevated levels of fat, sodium, simple sugars, and carbohydrates. These components contribute to their exceptional satisfaction upon consumption, often resulting in overeating due to their significant reward value.

The hypothalamic-pituitary-adrenal (HPA) axis is the primary neuroendocrine system in the human body that regulates stress response mechanisms (DeMorrow, 2018). It represents the interaction of the hypothalamus with the pituitary and adrenal glands and releases hormones during stress. In this course, the HPA will be discussed as an active component of the MGBA.

The hypothalamus is a region deep within the brain that serves as the body’s control center for maintaining homeostasis. It regulates various physiological processes, including appetite and energy balance, making it a key player in controlling food intake and metabolism.