Appetite Control System
Old systems in our brain regulate appetite, eating behaviors, and manage body weight. We call this brain device the Appetite Control System (ACS). The ACS integrates information about body weight, temperature, activity level, season, reproductive cycle (in women), food availability, and expected energy needs to decide how much food is needed today. See also Guide To Food Digestion.
Weight Set Point
ACS establishes a weight and temperature “set-point” and tries to maintain these values even when the food supply varies a great deal. This is a complex system that is based on the oldest of life-programs.
When ACS wants you to do something, you feel hungry and are driven to find food. ACS fools consciousness most of the time to think that you have some decision-making ability, but really most of your behavior is preprogrammed and run on auto pilot.
Appetite Control System
The appetite control system is based on programs in the old reptilian brain. This system is designed to establish the most efficient path to reliably available food, then to lock in the behavior and repeat it without further modification. Our appetite system tends to run automatically at this primitive level and defies conscious attempts to alter the program. Any insightful person will be able to track the importance of food searches in their own behavior. If you watch the people around you, you will readily confirm the primacy of feeding behaviors in human social existence.
The hypothalamus is a key brain region that integrates body-status information to determine the four-F behaviors. The hypothalamus receives chemical data from the blood and messages from various regulatory tissues in the body including insulin, sex hormones, and peptides secreted by GIT as it processes food. This appetite computer must integrate information about body weight, temperature, activity level, season, and reproductive cycle (in women) to decide how much food is needed. It is convenient to think that the system works by establishing a set point for body weight and then tries to maintain this value even when the food supply varies a great deal. A malfunctioning appetite computer might allow the setpoint to slide up or down causing overeating and obesity on the one hand or anorexia and progressive weight loss on the other.
This system shows a variety of two state transitions. The most basic feeding states are stop and go. The hypothalamus can be divided into two zones, a middle (medial) zone that tends to stop eating and inhibits aggression and a lateral zone which tends to turn eating on and excite (predatory) aggression.
In animal studies, damage to the medial hypothalamus produces animals who are irritable, eat too much, and become obese. Damage to the lateral go-system results in animals who eat little and tend to starve. The hypothalamus is also the brain link to the body’s hormonal network, regulating the pituitary gland, which in turn regulates the endocrine glands. Hormones are the blood-born molecules that regulate our metabolic and reproductive functions. The ingestion, digestion, and metabolism of food is one the chief concerns of the endocrine system. There are numerous opportunities for this regulatory system to fail. Often appetite and weight regulation is unstable for short periods of weeks but produces dramatic, lasting changes in size and shape.