Depression

How Obesity and Depression are Linked

The common knowledge, as quoted in several mainstream media sources, is that obesity causes depression and adversely, depression can also cause obesity. (1) (2) A Dutch study found that “there is a reciprocal association over time between depression and obesity.” (3) The findings suggest that overweight or obese people are more likely to be anxious, depressed and suffer from mood disorders. The Science Daily article suggests that “people who are obese may be more likely to become depressed because they experience themselves as in poor health and are dissatisfied with their appearance.” (4) The evidence further suggests that people who are depressed might be more likely to become obese because of physiological changes in their hormone and immune systems that occur during depression. (5) They also suffer from difficulties in taking good care of themselves, such as difficulty in sticking to exercise routines, overeating, and having negative thoughts. (6)

The social factors linking obesity and depression

The science behind this is quite fascinating. One study found that children between the ages of 9 and 16 who are overweight for a longer period of time tend to become depressed and have problems with their mental health. (7) Interestingly, the same study also found that young boys are more prone to obesity-related depression than young girls. (8) The article also suggests that the correspondence between obesity and depression could be due to social factors, or it could even be neuroendocrine-related. (9) Neuroendocrine cells are the cells in our bodies that link the neuronal and endocrine systems, transmitting molecule messages between the brain and the bloodstream. (10) This link suggests that the biochemicals found in our bloodstream have a direct relationship between the brain, that further suggests that the material entering the bloodstream from the digestive system has an indirect input into the way our brains work. Conversely, material leaving the brain and going through the bloodstream can then have a reverse effect. That is part of the reason why the obesity-depression link seems like a classic “chicken and egg” (11) situation.

The neurochemistry behind the obesity link to depression

The obesity-depression link has been found to mainly revolve around the hormonal pathway known as the HPA axis. (12) The hypothalamus, a peanut-sized part of our brains is responsible for communication with the pituitary and adrenal glands, both of which let out a variety of hormones. (13) This HPA axis is responsible for the release of cortisol into the body, which is called the “stress hormone” in lay terms. While this hormone plays a critical role in both metabolism and many other functions, it is also the responsible party for prompting the body to deposit fat around the abdomen. (14) Thus, a combination of social and biological factors seems to be responsible for the malfunctioning of the HPA axis. The things going on in your environment clearly have an influence on what is going on inside your body and thus put many people in the cycle of depression-obesity. This is especially true amongst children, where bullying and other social stigmas are more profound than in adult culture. Another factor that seems to exacerbate the problem, not just in children, but in adults as well, is that obese people tend to enjoy a quality of life less than that of people of normal weight. (15) So particularly children who are obese will not be able to take part in various activities such as physical education and sports, which make them “outsiders” to certain groups of children. This feeling of isolation can start the depression-obesity cycle that’s very difficult to get out of. (16)

The studies and the pure science

This knowledge that obesity and depression are intimately linked is by no means a new piece of information. Back in the 1960s, a study was conducted that showed that the more obese patients are the more likely they are to be depressed. (17)

Since then, with advances in molecular biology and biochemistry we have only discovered more and more the underlying biological and neurological reasons for this. For example, one of the earlier studies focusing more on social factors showed that when all other factors, such as “age, education, marital status, physician’s health rating, dieting for medical reasons, use of psychiatric medicines, cigarette smoking, and use of alcohol, marijuana, and cocaine” (18) were removed, patients who were depressed were identified also as obese in a 95% ratio.

In a more recent study, the HPA axis has even been linked to gene-environment interactions. (19) In other words, it is possible to affect not only the neuronal and endocrine (brain and body) systems by social stigmas and bullying associated with obesity and depression, but ultimately it may end up affecting the genetic code as well. (20) Perhaps one of the more important studies and one of the most recent is the one where a u-shaped correlation was found between obesity and depression. (21) The controversy was that some researchers found a correlation between obesity and depression, some did not and some found a negative correlation. (22) The elegant and simple solution was that obesity and depression are related using a u-curve graph, because it makes sense that an underweight person would suffer from depression just as an overweight person does, while a person with a normal BMI would not be suffering from depression. (23)

A good way to deal with obesity in children is to recognize the fact that obesity has nothing to do with appearance, but is a disorder that needs to be treated. (24) In dealing with children, parents need to record their children’s height and weight and teach them about the body mass index and make it a family exercise to stay at the right levels. (25) It should also be recognized that obesity is not necessarily caused by overeating. It’s a delicate chain and it’s all linked to the HPA axis. (26) In conclusion, the best way to combat depression and obesity in one convenient package is to switch to a healthy lifestyle that involves a good exercise regime and a controlled and healthy diet.

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(1) Obesity and depression are a two-way street, Megan Brooks, Thu Mar 4, 2010, Reuters. Retrieved July 6th, 2011, http://www.reuters.com/article/2010/03/04/us-obesity-depression-idUSTRE6234RF20100304
(2) Obesity And Depression May Be Linked, ScienceDaily, June 6, 2008, Science Daily. Retrieved July 6th, 2011, http://www.sciencedaily.com/releases/2008/06/080602152913.htm
(3) Obesity and depression are a two-way street, Megan Brooks. Retrieved July 6th, 2011, http://www.reuters.com/article/2010/03/04/us-obesity-depression-idUSTRE6234RF20100304
(4) Obesity And Depression May Be Linked, Science Daily. Retrieved July 6th, 2011, http://www.sciencedaily.com/releases/2008/06/080602152913.htm
(5) ibid.
(6) ibid.
(7) The Obesity-Depression Link, Willow Lawson, May 01, 2003, Psychology Today. Retrieved July 6th, 2011, http://www.psychologytoday.com/articles/200305/the-obesity-depression-link
(8) ibid.
(9) ibid.
(10) Neuroendocrine cell, Wikipedia. Retrieved July 6th, 2011, http://en.wikipedia.org/wiki/Neuroendocrine_cell
(11) Obesity and depression are a two-way street, Megan Brooks. Retrieved July 6th, 2011, http://www.reuters.com/article/2010/03/04/us-obesity-depression-idUSTRE6234RF20100304
(12) The Obesity-Depression Link, Willow Lawson, May 01, 2003, Psychology Today. Retrieved July 6th, 2011, http://www.psychologytoday.com/articles/200305/the-obesity-depression-link
(13) ibid.
(14) ibid.
(15) ibid.
(16) ibid.
(17) Obesity and depression., Leckie, E. V.; Withers, R. F, Journal of Psychosomatic Research, Vol 11(1), 1967, 107-115. Retrieved July 6th, 2011, http://psycnet.apa.org/psycinfo/1968-03649-001
(18) Is Obesity Associated with Major Depression? Results from the Third National Health and Nutrition Examination Survey, Chiadi U. Onyike, Rosa M. Crum, Hochang B. Lee, Constantine G. Lyketsos, and William W. Eaton, American Journal of Epidemiology Volume158, Issue12, Pp. 1139-1147. Retrieved July 6th, 2011, http://aje.oxfordjournals.org/content/158/12/1139.short
(19) Approaching the shared biology of obesity and depression: the stress axis as the locus of gene–environment interactions, S R Bornstein, A Schuppenies, M-L Wong and J Licinio, Molecular Psychiatry (2006) 11, 892–902. Retrieved July 6th, 2011, http://www.nature.com/mp/journal/v11/n10/abs/4001873a.html
(20) ibid.
(21) Depression and body mass index, a u-shaped association, Leonore M de Wit, Annemieke van Straten, Marieke van Herten, Brenda WJH Penninx and Pim Cuijpers, BMC Public Health 2009, 9:14. Retrieved July 6th, 2011, http://www.biomedcentral.com/1471-2458/9/14/
(22) ibid.
(23) ibid.
(24) The Obesity-Depression Link, Willow Lawson, May 01, 2003, Psychology Today. Retrieved July 6th, 2011, http://www.psychologytoday.com/articles/200305/the-obesity-depression-link
(25) ibid.
(26) ibid.