GENETIC

• WHAT IS OBESITY?

  being chronically overweight with excess body weight measured by BMI
• GENETIC EXPLANATIONS?

  • FTO gene
  • MC4R gene
  • evolutionary theory
• FTO GENE?

  • chromosome 16
  • regulates enzyme associated with fat mass and obesity
  • particular variant leads to obesity risk
  • higher ghrelin so hungry shortly after meals
• EVALUATION OF FTO GENE?

  + Frayling et al

  • 38000 Europeans genes
  • carriers of one risk variant of FTO weighed 1kg more on average
  • carriers of two risk variants of FTO weighed 3kg more on average
• MC4R GENE?

  • associated with body weight
  • produces protein which works with leptin to communicate to hypothalamus to stop eating
  • risk copy does not produce protein
• EVALUATION OF MC4R GENE?

  + GIANT consortium study

  • genetic data from 700000 individuals from 125 studies
  • 14 genetic variations of 13 genes
  • 1 in 5000 had risk variant of MC4R
  • weighed 7kg more on average

  + Turner et al

  • 9 year old obese boy
  • genetic data
  • part of MC4R deleted

  -only explains small number (160 million obese people in Europe, frequency of risk gene lower)
• EVOLUTIONARY THEORY?

  • pre-programmed to enjoy sweet foods
  • availability increased
  • inherited genes previously beneficial to ancestors
• EVALUATION OF EVOLUTIONARY THEORY?

  cross-cultural differences