13 August 2010

Genetic testing and obesity

Thanks to the Human Genome Project we now have a much clearer picture of how our genes impact on body weight.

"Genes load the gun; lifestyle pulls the trigger!"

A statement made by Dr Daniel Meyersfeld of DNAlysis at a recent ADSA Workshop on The Genetics of Obesity and Weight Loss, emphasises the interaction between our genetic makeup and lifestyle factors.

In other words, someone who has a genetic tendency to become overweight will react to negative lifestyle factors, such as a high-fat or high-energy diet and lack of physical activity, by gaining weight.

Amazingly it was found that the DNA of any two individuals in the world is 99.9% identical. So your DNA and that of your favourite film star only differ by 0.1%! But it is this very small variation in genetic material that influences how genes function which in turn determines various physiological body processes.

  • Genetic obesity, where the mutation occurs in a single gene and the person gains weight despite a non-obesogenic environment (an environment that does not encourage obesity). Only 1-5% of individuals who develop overweight or obesity have this type of mutation.
  • Strong disposition - persons who develop overweight in a non-obesogenic environment and obese individuals in an obesogenic environment (i.e. an environment that encourages obesity) 
  • Slight predisposition - persons with normal weight in a non-obesogenic environment and those that become overweight in an obesogenic environment 
  • Genetically resistant - people who maintain their normal weight even when they are exposed to an obesogenic environment.

  • Hunger and appetite
  • Eating behaviour (binge eating, overeating, etc)
  • Taste perceptions
  • Satiety (how full you feel after meals)
  • Spontaneous physical activity, such as fidgeting (fidgety movements can use up a large amount of energy)
  • Metabolic rate (the metabolic rate determines how much energy is used up to keep our bodies going and how efficiently we use up energy)
  • Thermogenesis
  • Motivation to exercise


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