From these areas, information projects to higher cognitive brain centers to ultimately regulate eating behavior (top red lines and boxes). The unconscious metabolic and visceral feedback (bottom blue lines and boxes) and the conscious reward feedback (left dashed and solid purple lines) are integrated within brain areas associated with aversion, cognition, reward, motivation, memory, and decision making (middle blue and purple boxes). Additionally, the mechanic distention of the gut is sensed by vagal afferents and projected to the brainstem to inform about the sensation of fullness. This peripheral metabolic feedback travels to the CNS as a signal of energy intake. However, once the food arrives at the gut lumen, it stimulates the release of gut hormones, such as peptide Y Y (PYY), glucagon-like peptide 1 (GLP-1), cholecystokinin (CCK), insulin, and others, based on the macronutrient composition of the food ingested. At this point, the energetic and macronutrient content of food has not been sensed. This information travels to the central nervous system (CNS) through a “fast” and conscious pathway. After food ingestion, sensorial information from food’s taste, smell, consistency, and temperature constitutes a second stimulus inside the oral cavity (post-ingestive stimuli (solid lines, purple or blue)). Food stimuli are perceived during a pre-ingestive (dashed lines, purple or blue) phase by the sense of sight, smell, audition, and touch. Integration of the hedonic and homeostatic components of food intake regulation. This regulation process depends on two different but closely intertwined processes: the homeostatic (i.e., metabolic) and hedonic (i.e., reward) components of food intake. The initiation, duration (termination of a meal), and timing (timing between meals) of eating episodes depend on conscious and unconscious neurohormonal processes, some from the internal milieu and others coming from the surrounding environment and decoded by the senses (e.g., sight, smell, taste).
These dynamic stages are controlled by the homeostatic and hedonic components of food intake regulation.įood intake is regulated by different organs and systems that project feedback of the individual’s metabolic status to the CNS, which ultimately controls this process ( Figure 1). Satiety is the process that inhibits eating in the postprandial period (inter-meal inhibition).
On the other hand, satiation is the process that brings an eating episode to an end (intra-meal inhibition). Hunger can be defined as the drive to consume. Food intake is divided into hunger, satiation, and satiety. Its regulation is synchronized by metabolic status and strongly influenced by reward circuitries within the central nervous system (CNS). This review focuses on the available neuroimaging evidence to describe this interaction between the homeostatic and hedonic components in human food intake regulation.Įnergy balance in humans is a complex process.
Neuroimaging studies allow us to take a glance into the central nervous system (CNS) while these processes take place. Identifying the interface between hormones, neurotransmitters, and brain areas is critical to advance our understanding of conditions like obesity and develop better therapeutical interventions.
This multi-level regulation process of food intake shapes and regulates human ingestive behavior. On the other hand, macronutrient composition stimulates the release of appetite signals from the gut, which are translated in the CNS into unconscious reward processes. On the one hand, sight, smell, taste, and texture perception deliver potent food-related feedback to the central nervous system (CNS) and influence brain areas related to food reward. Homeostatic regulation is controlled by appetitive signals from the gut, adipose tissue, and the vagus nerve, while conscious and unconscious reward processes orchestrate hedonic regulation. Food intake regulation in humans is a complex process controlled by the dynamic interaction of homeostatic and hedonic systems.
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