The Physiological and Emotional Factors Controlling Hunger

Hunger is the result of various emotional and physical factors that interplay in a complex manner. A combination of signals and associations are responsible for us being hungry at any time. Understanding these factors and signals can help you control your hunger and thus your weight and blood sugar levels.

Physiological Factors

A number of physiological factors influence how much we eat, when we eat and why we eat.  These include neurotransmitters and hormones.

The central nervous system (CNS) includes the spine and brain. The brain gives us the ability to make choices based on any number of criteria we receive from our senses. Our own experiences influence the senses of sight and smell to help us distinguish the types of food in front of us or being prepared in the kitchen, and the result is the stimulation of a flow of gastric juices.

Neurotransmitters and Hormones

Neurotransmitters are a collection of messenger chemicals.  They act as a relay system in the blood stream as they pass between locations in the nervous system. At certain points where a signal is made, the neurotransmitters are released. They act to pass the message from one neuron to another, so that the message is passed along to an end point. For example, if the stomach is full after a meal, neurons pass the message along to the hypothalamus gland which then responds appropriately.[1]

Understanding these actions allows researchers and medical professionals the means to develop and offer pharmacological answers to address any control issues such as over or under eating. Since overeating increases the risk of obesity which can lead to type 2 diabetes, it is beneficial to understand ways to control overeating.

Neurotransmitters and Hormones: Reducing the Urge to Eat

While the exact mechanisms are unknown, there are several hormones capable of reducing the urge to eat. Among them are the following:

  • Serotonin: Serotonin was first discovered in the blood serum, but it actually is found widely throughout the body. Tryptophan is absorbed from the intestines and passed through the blood-brain barrier. Once inside the CNS, some of the tryptophan is converted in incremental stages into serotonin. This hormone penetrates the nerve cells. Approximately 90% of all serotonin is located in the cells of the small intestine. Its activities are so plentiful it is difficult to define any one action.
  • Norepinephrine: The adrenal glands located atop the kidneys consist of two distinct parts with an inner medulla and an outer cortex. The medulla manufactures hormones called adrenaline (or epinephrine) and noradrenalin (or norepinephrine). These are the active chemicals of the sympathetic nervous system.
  • Leptin: This is a hormone formed in the fat cells (adipocytes or lipocytes). It appears to play a significant role in the activity of the hypothalamus concerning decreasing the amount of food eaten. Research indicates it causes a decrease in the hormones that provoke eating. It also acts to increase the metabolic rate and expenditure of energy as well as to lessen insulin secretion and therefore reduce the storage of energy foodstuffs. Leptin has been studied concerning type 2 diabetes. The research has not been conclusive on the ability it has as a potential aid in controlling obesity. In fact, there seems to be a leptin resistance, similar to that of insulin.
  • Insulin: Described elsewhere.
  • Cholecystokinin (CCK): The release of this hormone in the mucosa (inner surface) of the intestine wall is incited by fat and protein passing into the duodenum from the stomach. CCK has receptors in the hypothalamus as well as throughout the nervous system. It slows down digestion by slowing down the emptying of the stomach.

Neurotransmitters and Hormones that Increase the Urge to Eat

Just as you have neurotransmitters to prevent you from over eating, so too, do you have their polar opposite. These are neurotransmitters and hormones that increase the urge to eat.

  • Cortisol: The adrenal cortex produces cortisol under the direction of the hypothalamus by means of the anterior pituitary adreno-cortico-tropic hormone, ACTH.
  • Endorphins: Endorphins are essentially an endogenous (originates in the body) morphine group of hormones manufactured by the body for its own use. Among the many activities they have is one which opposes the actions of the neurotransmitters to inhibit feeding.

What Really Tells Us When We’ve Eaten Enough?

The stomach is a hollow bag of muscle.[2] Its walls possess stretch receptors, which signal the hypothalamus feeding center to slow down, which is why signals are sent when your stomach is full. In addition, the effects of both CKK and insulin on the hypothalamus reinforce the signal to stop eating. This is the basic physical process, but the physical concepts do not explain completely the various factors at work controlling hunger. People are more than the individual physical components of their body. They are affected by cultural and social factors as well.

The Emotional Aspects of Controlling Eating

Eating is not simply a physical act. While it does replenish our body’s requirements, it also plays a role in providing use with comfort e.g. comfort food. It is as much emotional or psychological as it is physical. Several theories address this. There are compulsive eaters, emotional eaters and those who eat as a result of conditioning or family influences. One study concludes that emotional eating is not emotional per se but “reflects beliefs about the relation between emotions and eating.”[3] Another theory proposes that those who cannot control food are suffering from an addiction.[4]

A more comprehensive approach takes into consideration various influences that include:

  • Socio-cultural factors
  • Biomedical or physiological (homeostatic) factors
  • Psychological factors
  • Medications[5]

Conclusion

If you want to control your hunger, you need to explore the diverse and complex actions that produce the need and desire to eat. Factors you need to understand to motivate you towards losing weight and keeping your diabetes under control are plentiful. In fact, there are many reasons why you eat, which is why many people have trouble losing weight or choosing the rights foods.  For your diabetes management program, it’s important to explore all the influences in your life that impact your desire to eat if you want to successfully control your weight and blood sugar levels. These influences include those that are physical, social, cultural or emotional. Once you have an idea of what is at work, you can get to work controlling your hunger.

References

[1] Murray, R.K;  Bender, DA; Botham, KM; Kennelly, PJ; Rodwell, VW; and Weil, PA (2009). Harper’s Illustrated Biochemistry 28th ed. New York: Lange McGraw Hill.

[2] Guyton, AC; and Hall, JE (2011). Textbook of Medical Physiology, 12th ed. Philadelphia: Saunders.

[3] Adriaanse, MA; de Ridder, DTD; and Evers,C (2011).“Emotional Eating: Eating when Emotional or Emotional about Eating?” Psychology and Health, 26 (1): 23-39.

[4] Taylor, VH; Curtis, CM; and Davis, C (2010). “The Obesity Epidemic: The Role of Addiction.” CMAJ, 182 (4): 327-328.

[5] Sharma, AM; and Padwal, R (2010). “Obesity is a Sign – Over-Eating is a Symptom: An Aetiological Framework for the Assessment and Management of Obesity.” Obesity Reviews, 11(5): 362–370.

This article was originally published July 12, 2012 and last revision and update of it was 9/10/2015.