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 is a psychological state characterized by a desire to eat (Stevenson, 2024). It strongly motivates an individual to seek out and consume food. Initially, researchers believed that it occurs when blood sugar levels drop and the stomach signals the brain to seek nourishment. More recently, feelings of hunger have been linked to an interplay between levels of various hormones, most notably ghrelin.

Stevenson, R. J. (2024). The psychological basis of hunger and its dysfunctions. Nutrition Reviews, 82(10), 1444–1454. https://doi.org/10.1093/nutrit/nuad092

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.

A condition in which there is an excess of androgens (male sex hormones such as testosterone) in females. It can cause symptoms like excess hair growth, acne, scalp hair thinning, and can contribute to menstrual irregularities and disorders such as PCOS.

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.

Immediate gratification refers to the desire for and pursuit of instant pleasure or satisfaction without considering or prioritizing long-term consequences. It involves seeking immediate rewards or benefits rather than delaying gratification for greater but delayed outcomes.

Immune cells are the active components of the immune system and belong to the white blood cell (WBC) category. They provide immunity to the host by protecting them from bacterial and viral infection and destroying the pathogen that enters the body.