Obesity

• obesity

  • abnormal or excessive fat accumulation that may impair health (WHO)
  • type of malnutrition
  • assessment methods vary by age, sex and ethnicity
• Asian populations

  • at BMI under 25 risk of T2D and CVD is much higher than caucasian
• Lancer (2004) recommendations for Asian populations

  • under 18.5 = underweight
  • 18.5 - 23 = increasing but acceptable risk
  • 23 - 27.5 = increased risk
  • over 27.5 = higher high risk
• android obesity = apple shape distribution, person stores fat around the abdominal region
• gynoid obesity = pear shape, excess fat is deposited somewhere at the thigh and hip areas
• android obesity (apple) increased risk of CVD than gynoid obesity (pear)
• waist circumference in men

  • desirable = under 94cm
  • high = 94 - 102cm
  • very high = over 102cm
• waist circumference in women

  • desirable = under 80cm
  • high = 80 - 88cm
  • very high = over 88cm
• obesity and diabetes

  • risk of diabetes increased with increased BMI
  • men with a BMI of 25 - 26.9 kg/m2 at 2.2x risk vs BMI over 35kg.m2 risk rate of 42.1x
• overweight classification for children UNDER 5 (weight for height) = 2 standard deviations above WHO growth chart

  • above 85th percentile
• classification for children OVER 5 = 3 standard deviations above the standards or over 97th percentile

  • children aged 5-19 = BMI for age
  • overweight = over 1 standard deviation above the WHO growth reference median
  • obesity = over 2 standard deviations above the references
• visceral adipose tissue more strongly correlated than subcutaneous adipose tissue with hypertension, raised fasting glucose, triglycerides, diabetes
• the INTERHEART study - obesity and CVD

  • smoking - odds ratio = 2.87
  • central obesity - odds ratio = 1.1 - 1.6
  • hypertension - odds ratio = 1.91
  • diabetes - odds ratio = 2.37
• energy balance = energy intake - energy expenditure
• energy balance

  • body weight can only change when energy intake is not equal to energy expenditure over a given period of time
  • metabolism is not a factor of obesity - energy expenditure only becomes less than lean people when obesity is severe and limits movement
• genetic factors of obesity & CVD

  • increase the risk of developing a characteristic but are not essential for its expression
  • some lifestyle behaviours are protecting and decrease the risk; others increase the risk
  • Bardet-Biedl syndrome
  • Prader-Willi syndrome
  • candidate monogenic gene
• Bardet-Biedl syndrome

  • similar characteristics to Prader-Willi
  • highly heterogenous: studies have identified several different chromosomal loci in different families responsible for the syndrome (chromosomes 16, 11, 3, 15)
• Prader-Willi syndrome (PWS)

  • 1 in 25000 births
  • usually associated with familial inheritance
  • caused by a deletion of the paternal segment of chromosome 15
  • upper-body obesity, short stature, mental retardation, hypogonadism
• example of candidate monogenic gene: leptin

  • satiety hormone: controls food intake by making you feel full - circulates in blood and signals to the brain
  • very few cases of leptin deficiency in obese humans
  • more cases of high circulating leptin concentrations found than in non-obese