Genetic Testing & Obesity
Obesity is now acknowledged as a medical condition that can occur in families and is possibly caused by one or a combination of 11 very rare genetic traits that increase a person's chance of developing obesity. Genetic testing for obesity, while still a highly unusual procedure, can provide valuable information to aid both sufferers and their carers.
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Obesity
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An obese individual is one who has a body mass index exceeding 30kg per square meter, and it is thought that by 2015, the number of individuals who fall into this category will increase to more than 700 million. At least 32 percent of Americans are obese, and annually, at least 100,000 deaths are associated with the condition. Obesity in adults is a concern as it puts the individual at greater risk of more complicated and severe secondary medical conditions, such as diabetes, cardiovascular disease, cancers and osteoarthritis.
Genetic Causes
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Obesity that occurs in families is thought to be due to the effects of one or more genes, which can be inherited. In the case of a single gene causing rare genetic conditions including Cohen syndrome and Prader Willi syndrome, deficiencies such as leptin or leptin receptor deficiency and mutations such as that found in the melanocortin-4 receptor gene, obesity can begin in childhood. More commonly, it is traced back to a collection of single variations in the DNA, known as single nucleotide polymorphisms (SNPs), of which 11 have now been identified and associated with hereditary obesity.
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Genetic Testing for Obesity
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Genetic testing does not test for obesity itself, since the condition is not classified by a single genetic trait. Instead, it involves detecting the genetic conditions (Prader Willi. for example) that are associated with the obese physical trait. Clinical genetic tests are best carried out by trained medical geneticists, and the results are interpreted in collaboration with genetic counselors, who will eventually help the patient understand the test results. The geneticist performs an experiment called a whole genome scan, which looks for SNPs in the patient's genome that may be associated with obesity or the medical conditions related to obesity.
Issues
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It is crucial to note that scientists, clinicians and medical geneticists consider genetic testing for obesity to be useless and medically irrelevant as far as obesity is concerned, since this disorder is linked to too many genetic factors with unavailable treatments and unknown causes. Instead, health-care professionals regard genetic testing for obesity as merely informational, and do not factor the test results highly in their treatment procedures, unless and until the patient displays more severe complications that may be linked to obesity. Another issue is the availability of home-testing kits. These kits do not provide a diagnosis of any medical condition, and are only capable of detecting whether a gene is present or absent. They are highly inaccurate, often detecting the wrong genes or detecting variants of disease-causing genes. Few kits provide diagnosis and/or genetic counseling services, which tell the patient what to do to get help if he possess or is missing a gene. Furthermore, simply because a person has a genetic deficit does not mean that he will develop a disease or a severe version of the disease.
Sources of Genetic Testing
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Genetic testing for obesity is not recommended. However genetic testing for the secondary and associated conditions is supported by hospital clinics and several private companies, such as deCODE, Navigenics and 23andMe. These companies do offer genetic counseling, but again, the counseling falls short of medical recommendations and therapeutic interventions, only informing the patient whether she has a genetic risk for a particular condition. All university medical centers will either have their own genetics testing facility or links to one, such as the University of Kansas' Clinical Genetics Services, Clinical Genetics at Yale University School of Medicine, the Genetic Counseling Clinic for Minority Women at the San Francisco General Hospital and the Center for Human Genetics at Boston University School of Medicine.
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