"A Cure for Genetic Obesity?" - Sebastian Campbell
Farooqi, IS & O’Rahilly S 2005, ‘New advances in the genetics of early onset obesity’, International Journal of Obesity, vol. 29, pp. 1149-1152 (*)
As of 2008, Australia is the “fattest country on earth” (1), with 26% of Australians considered obese. According to the World Health Organization (2), overweight is defined as an individual with a “BMI greater than or equal to 25” while obese is defined as an individual with a “BMI greater than or equal to 30”. The purpose of this blog is to discuss the link between genetics and early onset obesity, and the recent advances in genetics that have allowed the treatment of such genetic disorders.
It was once thought that obese individuals were the result of poor diet and lifestyle, and lacked self-control. Obesity is an evolutionary artifact from a time when it was an advantage to be able to store fat in anticipation of famine. Recent studies have found that BMI and weight, like other heritable traits such as height and hair color, may in fact be up to 70% heritable (3). Therefore some people are predisposed to having high BMI’s and suffering from obesity as a result of the genetics of their parents. The only way to unequivocally prove that an individual is obese as a result of a genetic disorder is through genetic screening.
If a child displays hyperphagia (insatiable appetite and high food intake) and an unusually high BMI, then it is likely that the child suffers from a genetic disorder. The most common genetic disorder linked to obesity is leptin and leptin receptor disruption or deficiency. Leptin is hormone produced by fat tissue cells that suppresses appetite. More fat cells result in greater leptin production and more appetite suppression. Less fat cells result in decreased leptin production and less appetite suppression. Leptin deficiency occurs from a single gene mutation on the long arm of chromosome 7 region 3, band 1, sub-band 3 (4)
Figure 1. A Leptin Molecule (5)
Leptin receptor is a protein that detects leptin levels in the body and both normal leptin production and accurate leptin reception are vital to the correct moderation of fat tissue levels in the body.
While obesity is the most common symptom of leptin and leptin receptor deficiency, other features of the disorder include central hypothyroidism (a drop in the amount of thyroid hormone in the body) and hypogonadotropic hypogonadism (where the sex/reproductive glands produce very little or no measurable hormones).
Recent advances in the field of diagnostic and clinical genetics have allowed for the treatment of individuals suffering from leptin and leptin receptor deficiency. The most widely used treatment involves the injection of recombinant human leptin produced in E. coli and administered in subcutaneous injections, similar to insulin injection in diabetics. Such treatment represents the first hormone modification treatment for genetic and in fact any type of obesity.
Figure 2. The Results of Recombinant Human Leptin Injections on a Child Suffering from Leptin and Leptin Receptor Deficiency (*)
In conclusion, genetic testing is the only way to confirm that an individual’s obesity is the cause of a genetic disorder and leptin injections represent the first and only current treatment for genetic obesity.
(1) Sydney Morning Herald June 20 2008, ‘Australia pips US as world's fattest nation’ retrieved 16th March 2012 from: <http://www.smh.com.au/news/health/australia-pips-us-as-worlds-fattest-nation/2008/06/19/1213770827371.html>
(2) World Health Organization March 2011, ‘Obesity and Overweight’ retrieved 16th March 2012 from: <http://www.who.int/mediacentre/factsheets/fs311/en/>
(3) Barsh, GS, Farooqi IS, & O’Rahilly, S 2000, ‘Genetics of body-weight regulation’, Nature, vol. 404, pp. 644-651
(4) National Center for Biotechnology Information 2012, Leptin (LEP), Viewed 15th March 2012,
(5) Davidson College Department of Biology 2005, ‘Leptin’ retrieved March 16th 2012 from: <http://www.bio.davidson.edu/Courses/Molbio/MolStudents/spring2005/Amore/leptin.html>
(*) Farooqi, IS & O’Rahilly S 2005, ‘New advances in the genetics of early onset obesity’, International Journal of Obesity, vol. 29, pp. 1149-1152