Created by: Uteller King, Najm Villanueva, Julia Winsor



Research in the genetic factors of obesity has just begun. 350 genes or gene markers have already been identified that are associated with obesity. In many cases, obesity cannot be targeted to just one simple cause, often times many different genes, disorders and conditions are contributing factors. Environmental factors seem to be a critical factor for the expression of the genetic potential (Centers for Disease Control and Prevention [CDC], 2009). Considerations regarding the many different factors contributing to obesity are critical in understanding and treating this disease; through manipulation of exercise and activity, endocrine and metabolic conditions, genetics and CNS disorders as well as strict regulation of diet.


Genetics

Our body’s central nervous system (CNS) plays a major role in regulating weight, appetite, and energy expenditure. Along with this and other behavioral aspects, the CNS activates six genetic variants strongly associated with the Body Mass Index: TMEM18, KCTD15, GNPDA2, SH2B1, MTCH2 and NEGR1. Four out of these six variants were found to be associated with adult and childhood obesity and the predisposition for its manifestation.

Genes are basic units that are capable of transmitting characteristics from one generation to the next. Genes determine hair and eye color, how tall we will be and eventually, our weight. Factors of being obese are not alway due to overeating, but may be due to hereditary. This genetic predisposition puts individuals at risk for becoming obese from the time of birth if their parents are obese.

An aspect that is involved with this inherited trait is partially due to thrifty genes. Ironically, thrifty genes were evolutionarily selected in our advantage. High levels of physical activity was not merely for recreational sport as it is utilized today in the U.S. These genes allowed us to support a certain energy level that was essential for survival in hunter-gather societies. For example, thrifty genes gave us the ability to function in times famine. Fatter people were better able to survive in times of food-scarcity. In food abundance, women of childbearing years were better able to ‘fatten-up’ so to speak, for child rearing.


Drastic changes in today’s physical environment, activity levels and food availability over the past century, particularly in the U.S. has led to discordance in the ways our genes interact with the environment. These genes were not adapted for the sedentary lifestyle that many Americans have aquired today, therefore, a genetic characteristic once essential for surviving famine has ultimately become detrimental in the modern world. This reality has eventually led to the epidemic of modern chronic diseases that we see today; ranging from heart disease, type 2 diabetes, metabolic symdrome and cancer (2).


Visit this link for more information on genetics and its association with obesity: www.cdc.gov/genomics/resources/diseases/obesity/index.htm

U.S Department of Health and Human Services, National Institute of Health: http://www.nih.gov/news/health/dec2008/nhgri-14.htm



Psychological


Did you know that food plays a huge role in the psychological aspect of obesity? Many people suffer with psychological problems such as boredom, depression, anxiety, stress, trauma and low self-esteem. Though, most people who are obese resort to food as an escape from their problems. This is commonly called binge eating which is an eating disorder. Those who suffer from this disorder feel deprived and choose to eat high fat foods. They prefer to put taste and convenience ahead of adequate nutrition. After binge eating they then start to feel depress and experience insecurity, due to gaining more weight (3, 5).


There is an overflow of Fastfood restaurant chains such as McDonald's has gained great popularity across the country, especially, in the eastern region of the United States. One question we must ask ourselves is, are there an equal amounts of parks compared to McDonalds in these communities?


Most obese individuals carry psychological damage from their childhood. In some cases, obesity can be the result of boredom or an unfulfilling lifestyle. It may be that the individual is unable to find anything else to do that might make them happy, thus, comfort is found in food. This is a continuous cycle that continues to contribute to the psychological aspect of obesity (4).

This obesity epidemic can be controlled by teaching obese people how to live a healthier lifestyle that includes the recommended nutrients and food portion as well as daily exercise and by recognizing and controlling environmental influences.

For more information on the psychological aspects of obesity visit:

Centers for Disease Control and Prevention:
Http://www.CDC.gov/obesity/causes/index.htm/


Physiological

Human physiology is a science of a wide scope, and can be broadly defined as the study of the processes and functions of living persons and their parts, with the principle level of focus being that of the organs and organ systems. This includes the mechanical, physical and biochemical processes of organs, tissues and the cells of which they are composed. The body is a complex collection of many interacting systems, each having its own functions and processes, that integrate and overlap, regulating physiology. Physiological studies may be concerned with processes that go on within cells, others deal with how tissues and organs work, how they are controlled and interact with other tissues and organs, and some deal with the human body and it’s response to the environment and different environmental factors. Nevertheless, the foundation for studying human physiology and everything in nature is the same, its done within the respect to its effect on human life. Obesity is thought to simply be the lack of willpower or discipline with regards to ones eating habits and therefore caused by ingestion of food greater than that of the body’s energy requirements, but in reality it is a complex condition resulting from an interaction of multiple genetic, environmental, physiological, psychological and social factors.

Physiological aspects contributing to the growing epidemic of obesity; endocrine disorders, genetic syndromes (discussed previously), disorders of the central nervous system, and mulitfactorial causes of obesity (caused by an interaction of multiple genes) (6).


Endocrine disorders

The endocrine system is a system of glands including the hypothalamus, pituitary, thyroid, adrenals and testicles or ovaries that release hormones and secrete them into the circulatory system through which they travel to affect organs. The endocrine system is instrumental in regulating mood, growth and development, tissue function, metabolism, as well as sexual function and reproductive processes (6). Hormones can be thought of as the body’s chemical messengers, transferring information from one cell to the other. These hormones can be affected by infections, stress, and changes in the balance of fluids and minerals within the body. Too much or too little of a hormone can have negative consequences to the body, often leading to abnormalities such as obesity. By controlling the production of certain hormones, or through replacement of hormones, it is possible to treat many endocrine disorders.


The following are Endocrine disorders and links to more information:


Cushing Syndrome- http://endocrine.niddk.nih.gov/pubs/cushings/cushings.htm
Diabetes-http://www.diabetes.org/
Hyperthyroidism- http://www.endocrineweb.com/hyper1.html
Growth Hormone Deficiency-http://emedicine.medscape.com/article/923688-overview
Precocious Puberty- http://emedicine.medscape.com/article/924002-overview


Central Nervous System Disorders

Injury to the Central Nervous System (CNS) resulting from accidents or neoplasms has been known to cause obesity in a small number of patients (Goldstein, 2005, p.113). Pituitary or hypothalamic tumors are the most comon types of neoplasms associated with the onset of obesity. Surgical procedures within the CNS have resulted in the onset of obesity as well, such as a tonsillectomy. Certain infectious dieseases have resulted in obesity, tuberculosis and other bacterial diseases are rare, but may result from infection of the CNS with anatomical damage. Viral infections such as measles have caused obesity in animal induced studies (Goldstein, 2005, p.114).




References:

1. Centers for Disease Control and Prevention. 29 Dec 2009. Centers for Disease Control (CDC), Web. 13 Oct 2009.

2. Chakravarthy MV, Booth FW. Eating, exercise, and "thrifty" genotypes: connecting the dots toward an evolutionary understanding of modern chronic diseases. J Appl. Physiol. 2004;96(1):3-10

3. Wadden TA, Stunkard AJ. Social and Psychological consequences of obesity. Ann Inter Med 103: 1062-7.

4. Leon GR. Roth L. Obesity: Psychological causes, correlations, and speculations. Psychol Bull 1977;84:117-39

5. Silverstone JT. Psychological Aspects of Obesity. Proc R Soc Med 1968;61:371-5

6. Goldstein, David. "The Management of Eating Disorders and Obesity." Google Books. 2005. Humana Press, Web. 13 Oct 2009. http://books.google.com/books?id=yRnjYuawT7kC&printsec=frontcover#v=onepage&q=&f=false.

7. "The Physiology of Obesity." The ABNF Journal. June 2003. Web. 30 Nov 2009. Your online source for credible Health information.