Monday, 2 August 2010

Obesity - disease or lack of willpower?

Debate rages over whether obesity is caused by lifestyle or is actually a disease.

A lot of research has pinpointed genetic factors that are associated with obesity and even some behaviours. Certain changes in DNA are strongly correlated with the incidence of obesity, such as the deletion of DNA from chromosome 161 and specific changes in single nucleotides in 13 different genes in the human genome.2 A research group in Spain has found a strong association between single nucleotide polymorphisms (SNPs) in a gene related to the circadian clock3, and cessation of a weight-reduction program. These SNPs were also associated with extreme snacking, eating when bored, skipping breakfast, and abdominal obesity.

The value of this research lies in the potential to tailor weight-loss programs to the individual. At the Nutrition, Physical Activity, and Metabolism 2010 conference held in March in San Francisco, data was presented showing that people responded better to diets when these diets were assigned based on their genotype, instead of randomly.4

Subjects were put on either the Atkins, Ornish, Traditional, or Zone diets, and the presence of specific forms of three different genes were determined. There was a strong and significant correlation between certain genotypes, a specific weightloss regime, and amount of weight lost. The proportion of people who responded well to low-carb diets compared to those who responded well to low-fat diets was approximately 50-50.

So your genes might tell you whether you're predisposed to gaining weight. It can also help you to choose strategies to manage weight loss. Increasing knowledge of the links between genes and disease allow for the development of more sophisticated drugs and treatments.

1Walters R.G. et al. A new highly penetrant form of obesity due to deletions on chromosome 16p11.2. Nature 463, 671-675 (2010).
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2Cheung C.Y.Y. et al. Obesity Susceptibility Genetic Variants Identified from Recent Genome-Wide Association Studies: Implications in a Chinese Population. The Journal of Clinical Endocrinology & Metabolism 95: 1395-1403 (2010).
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3Garaulet M. et al. PERIOD2 Variants Are Associated with Abdominal Obesity, Psycho-Behavioral Factors, and Attrition in the Dietary Treatment of Obesity. Journal of the American Dietetic Association 110: 917-921 (2010).
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4O'Riordan M. Dieting by DNA? Popular diets work best by genotype, research shows. Heartwire (2010)
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