An odor one is not consciously aware of.

Amino acids are the basic building blocks of proteins, consisting of a central carbon atom bonded to an amino group (-NH2), a carboxyl group (-COOH), and a unique side chain (R group) that distinguishes one amino acid from another. They play crucial roles in various biological processes, including protein synthesis, enzyme function, and as precursors to neurotransmitters and other essential molecules in the body.

The amygdala is a small, almond-shaped region deep within the brain that plays a central role in processing emotions, particularly fear and anxiety. It also contributes to assessing the emotional significance of experiences, including those related to food and dietary choices.

Anhedonia is the inability to experience pleasure from usually pleasurable situations, and it is a primary symptom of depression, schizophrenia, and other mental disorders (Sharma et al., 2004).

Anorexia nervosa is an eating disorder characterized by self-imposed restriction of energy intake, leading to a significantly low body weight. Individuals with anorexia have an intense fear of gaining weight and exhibit a distorted perception of body image, often failing to recognize the severity of their low weight. This disorder can result in serious physical and psychological health complications, requiring a multidisciplinary approach to treatment, including nutritional support and psychotherapy.

The anorexigenic peptides are derived from the Greek words ἀν- (an-, “without”) and ὄρεξις (órexis, “appetite”), meaning “without appetite.” They are primarily produced in the stomach to suppress appetite and food intake (Sobrino Crespo et al., 2014).

The term “anorexigenic” is derived from the Greek words ἀν- (an-, “without”) and ὄρεξις (órexis, “appetite”), meaning “without appetite” and referring to “appetite-suppressing” hormones produced to suppress appetite and reduce food intake, such as GLP-1, CCK, and PYY (Sobrino Crespo et al., 2014).

Antibiotic-induced microbiota depletion (AIMD) refers to the administration of one or more antibiotics that deplete the microbiota and disrupt the microbial balance, including richness and diversity. This can harm host health by increasing susceptibility to pathogen infection (Modi et al., 2014). This procedure is often used to investigate the role of gut microbiota in some pathological conditions (Patangia et al., 2022).

Antibodies, also known as immunoglobulins, are proteins produced by B-cells in response to the presence of antigens. They bind to specific antigens, marking them for destruction by other immune cells.

Antigens are molecules or molecular structures, often found on the surface of pathogens, that trigger an immune response. They stimulate the production of antibodies or the activation of immune cells.