Obesity Flashcards
What units are BMI measured in?
Kg/m2
What issues are found with BMI?
Inability to differentiate muscle from fat and further to this, the distribution of body fat (high waist circumference indicates higher risk – ‘android’ obesity vs gynoid obesity). Ethnicity may increase risk of comorbidities – hence a different BMI index for those of Asian background
Why is obesity classified as a disease?
It is associated with increased risk of morbidity and mortality. for each increment of 1 in BMI, there is an increase heart failure risk of 5% in men, 7% in women
How are classes 1,2 and 3 of obesity classified? How are Asians classified?
Class 1 Obesity = 30-34.9, Class 2 Obesity= 35-39.9 and Class 3=40-50, morbid obesity.
Above 25 is considered obese and above 30 is severe obesity.
How is waist circumference measured, how effective is it as a measurement?
Mid-point between lowest
rib & iliac crest - ~1cm above naval, better than BMI. Indicates a potential impact on liver, glucose and lipid metabolism and
& insulin release.
Why does abdominal obesity lead to increased CHD?
• Abdominal obesity is associated with greater:
o Insulin insensitivity: insulinaemia and glycaemia
o Abnormal lipid profile
o Susceptibility to thrombosis
o Inflammation markers
o Endothelial function
What should be done at waist circumference action level 1 and 2?
What should be done at waist circumference action level 1 and 2?
If waist circumference is at action level 1 (W=>80cm, M=>94cm) the health risk is increasing and personal action should be taken to avoid weight gain. Action level 2 (W>88cm, M>102cm) has multiple health problems and need professional help.
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Why is being overweight and obese so common?
- Food is cheaper, so there’s increased snacking
- Increase in proportion of foods derived from fat and increased energy density
- Energy intake is greater than expenditure
- Increasing inactivity amongst people and a mismatch between greatly decreased energy requirements and inability of physiological mechanisms to down regulate energy intake to a similar extent
- Thrifty gene hypothesis to select those wth the ability to survive famines, ie obese; very few systems say stop eating
What’s the main cause of premature death in obese people?
Ischaemic heart disease; hypertension, coronary thrombosis and congestive heart failure are more likely. CHD is the biggest killer.
Obese women are 3x as likely to have MI and men & women are 2x as likely to experience angina than non-obese
What other conditions has obesity been linked to?
1. Cancer, through effects on hormones • Breast, endometrial, stomach, colon 2. Type 2 Diabetes (80x more likely to develop) • 80x more likely • 3. Osteoarthritis • Hips, knees • >2x more likely 4. Mental health • Obese women less likely to be hired or promoted or receive positive performance reviews and have a higher incidence of depression 5. Infertility/PCOS 6. Gallstones due to improper gall bladder emptying and/or excess cholesterol and/or bilirubin and/or a lack of bile salts, in bile 7. sleep apnoea 8. gout
How is obesity related to energy expenditure?
energy intake > energy expenditure for extended period of time
What are the 3 components of energy expenditure?
1. Resting metabolic rate/obligatory expenditure – 50-70% Correlated to body weight 2. Thermogenesis – 5-15% Linked to temperature and diet 3. Physical activity – 20-40%
Why does BMR increase with body weight
This is because increase in weight is not just fat, usually about 25% is lean tissue, comprising heart, skeletal muscle, and enlargement of GIt and liver.
What are the molecules in the CNS that tightly regulate body weight?
It’s likely we have a hypothalamic set weight. The hypothalamus integrates metabolism and receives neural and hormonal inputs.
Lateral Hypothalamus feeding centre
Orexigenic/anabolic:
Neuropeptide Y (NPY)
Agouti-gene related Peptide (AGRP)
Melanin-concentrating hormone (MCH)
VMH satiety centre
Anorexigenic/catabolic molecules
Leptin receptor (LEPR); leptin is synthesized in fat and results in less cortisol, insulin and food intake and increased energy expenditure.
Pro-opiomelanocortin (POMC)
Melanocortin receptor 4 (MCR4)
Glucagon-like peptide 1 receptor (GLP-1R)
¥ CASE STUDY: Framingham study revealed that average body weight increases by less that 1 lb per year from age 25-55
What are the molecules in the peripheral tissues that tightly regulate body weight?
Skeletal muscle o Myostatin, myogenin Brown adipose tissue o Uncoupling protein 1 (UCP-1) White adipose tissue o Leptin, lipoprotein lipase Gut o Glucagon-like peptide 1 (GLP-1) ¥ CASE STUDY: Framingham study revealed that average body weight increases by less that 1 lb per year from age 25-55
