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Research Shows How Brain Can Override Hunger in Eating Disorders
Those individuals with anorexia and bulimia have brains that function differently in order to restrict eating from their non-eating disordered peers. Dr Guido Frank from the University of Colorado Denver, was the lead author on a study which indicated that the brains of those with eating disorders show significant alterations, suggesting that the brain overrides hunger signals [1].This study tested brain structure and function, using brain activation data, with those with and without eating disorders.
The participants tasted certain sugars meant to activate hunger cues in the brain, and the sugar consumption showed a reverse effect for those participants identified as having anorexia and bulimia. In a non-disordered brain, typically the hypothalamus motivates an individual to eat. In those with an eating disorder, signals from other regions of the brain override the signal in the hypothalamus. This indicates that the brain can reject signals, including taste-reward and hunger [1].
Understanding How the Brain Regulates Hunger
There are several processes that need to be defined to understand the brain’s ability to override hunger [9]. Satiety is defined as the continuation of fullness and suppression of hunger between meals. Satiety begins after the end of eating and prevents further eating before the return of hunger.
Satiation is the development of fullness and reduction of hunger during a meal. Satiation occurring during an eating episode and brings it to an end. The hypothalamus is the brain’s center for controlling energy balance. Hedonic circuitry if the are of the brain which can override energy balance systems.
Food can provide a powerful visual, smell, and taste signal which can override satiety and stimulate feeding [2]. Taste receptors convey information of foods to the NTS and parabrachial nucleus in the brainstem. It is then relayed to the thalamus and lateral frontal cerebral cortex and then onto the hypothalamus area. Eating behaviors are activated by hunger, cravings, and sensations.
Energy homeostasis is controlled mainly by neuronal circuits in the hypothalamus and brainstem, whereas reward and motivation aspects of eating behavior are controlled by neurons in limbic regions and cerebral cortex.
The food homeostasis is an integrated system, where metabolic signals, gastrointestinal tract and peripheral organs target the brain to regulate feeding, energy expenditure and hormones. Energy balance is the ability of the brain to detect the levels of energy stores and match energy intake with expenditure. Anorexia is typically characterized by anhedonic eating.
Research Investigations and Findings
Previous research showed that the anorexic brain ‘likes’ food, but do not ‘want’ food in the way that non-eating disordered individuals do [7]. The way reward and food is experienced by the anorexic brain has partial reward to food, and punishment behaviors, such as starvation and over exercise are stronger.
Further research in 2013 indicated that partial weight restored anorexia patients were less like to ‘want’ high calorie foods and felt a higher desire to lower calorie foods [7]. In this study, wanting was measured by the patients identification of wanting a food from not at all to extremely in a response-question format. In this study, there was decreased motivation to eat high calorie foods and increased incentive to eat low calorie foods. This suggested that the sensory pleasure of eating is still there, but it is overridden by brain inputs [7].
At Cambridge University a gene that controls a person’s desire for food was identified. Leptin, which is the gene that is responsible for the feeling of fullness and a desire for food. Those individuals that have a Leptin deficiency, the desire for food can be so overwhelming that it can override the normal cues that curb eating, causing a person to overeat [8]. Research in this area has also shown that participants with a Leptin deficiency were shown pictures of food, such as chocolate cake, pizza, etc., heightened activity was noted in the areas of the brain that are responsible for reward, pleasant emotions, and desires.
Recent research from the University of Colorado, Denver also gives insight into how the brain can override hunger. In this study, the researchers discovered that those individuals with eating disorders had widespread alterations in the structure of the brain pathways that govern taste-reward and appetite regulation [3].
The alterations were specifically found in the white matter which coordinates communication between the different parts of the brain. In non eating disordered individuals the hypothalamus was responsible for the cues in the areas within the brain that drive eating, whereas those with eating disorders, the pathway to the hypothalamus were significantly weaker and the direction of the drive to eat were reverse.
Emotional State of Hunger
When our bodies are in a homeostasis state, we tend to experience positive emotions and feelings, compared to when our bodies are in fight or flight mode, we tend to experience negative or distressing emotions and feelings. When we are a distressed mode, our brains and bodies are out of balance [5].
When this is applied to our brains and need for food, and the starvation state, our body sends a signal to our brains that creates a sensation of hunger, which is an emotional state of hunger. The hypothalamus is the energy balance center in our brain [9]. This function tries to maintain energy balance and prevent starvation.
According to Dr. Frank, the appetite region of the brain should signal to our bodies to eat, but those with eating disorders begin avoiding eating for fear of gaining weight [4]. This could be a learned behavior with weight gain as the feared punishment (think operant conditioning), and the behavior eventually could alter the brain’s pathways that govern appetite and food intake. Current research suggests that being afraid to eat could in fact impact the taste-reward processing in the brain.
In conclusion, our bodies and brains is a complex system of signals and needs. When the anorexic patient is in a starvation mode, the brain’s ability to reverse the feeding signal is powerful and more thought to be genetically based.
As future research goes forward it will be interesting to see if this neurological process is reversible within the brain structure. It will also have further implication for pre-identification of eating disorders and possible prevention.
About the Author: Libby Lyons, MSW, LCSW, CEDS is a specialist in the eating disorder field. Libby has been treating eating disorders for 10 years within the St. Louis area, and enjoys working with individuals of all ages.
References:
[1] https://www.nationaleatingdisorders.org/blog/new-study-explains-how-those-eating-disorders-can-override-hunger-cues[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710609/
[3] http://neurosciencenews.com/neuropathways-eating-disorders-5446/
[4] https://www.sciencedaily.com/releases/2016/11/161108120412.htm
[5] https://www.psychologytoday.com/blog/the-embodied-mind/201209/emotions-survival-and-disconnection
[6] http://www.webmd.com/diet/features/really-hungry#1
[7] https://www.psychologytoday.com/blog/hunger-artist/201405/what-anorexics-really-feel-about-food
[8] http://www.bioethics.ac.uk/news/scientists-discover-the-hunger-gene.php
[9] http://www.full4health.eu/documents/Hunger__satiety_Amin__Mercer_FST.pdf
The opinions and views of our guest contributors are shared to provide a broad perspective of eating disorders. These are not necessarily the views of Eating Disorder Hope, but an effort to offer discussion of various issues by different concerned individuals.
We at Eating Disorder Hope understand that eating disorders result from a combination of environmental and genetic factors. If you or a loved one are suffering from an eating disorder, please know that there is hope for you, and seek immediate professional help.
Reviewed By: Jacquelyn Ekern, MS, LPC on March 17, 2017.
Published on EatingDisorderHope.com
The EatingDisorderHope.com editorial team comprises experienced writers, editors, and medical reviewers specializing in eating disorders, treatment, and mental and behavioral health.
