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Flashcards in MCP 9 Deck (20)
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how to define and measure obesity?

BMI (kg/m2)
waist circumference
waist to hip ratio
waist to height ratio
body shape index


why is obesity a problem?

-risk factor for development of type 2 diabetes mellitus
-obstructive sleep apnea
- joint diseases, gallbladder disease, reproductive disorders, 20% of cancer deaths
-cardiovascular diseases
-psychological stress


genetic causes of obesity

polygenic: product of many genes are involved in controlling body weight


environmental causes of obesity

diet, exercise. consequence of industrial revolution


lipostat hypothesis

regulation of weight around a set point. set point is determined by genetic factors and can be reset by environmental factors leading to weight gain.

1. a signal that monitors fat stores: leptin (made by adipocytes)
2. a sensor: brain cells in hypothalamus express leptin receptors
3. effector systems: hypothal centers influence energy intake and expenditure by releasing effector molecules


wild type ob gene

encodes a protein, leptin, produced and released by adipocytes. highly conserved in many vertebrate species. ob mutation results in truncated inactive protein. ob/ob mice behave as if starved, causing an increase in weight and body fat


wild type db gene

encodes for the leptin receptor. db/db mice dont produce the receptor. mutation results in a defective receptor


injections of leptin into ob/ob mice

decreased feeding and body weight, increased energy expenditure


how does leptin work?

acts on CNS to trigger food intake and energy utilization. reduces production of orexigenic effectors made by AgRP neurons. increases production of anorexigenic effectors by POMC neurons


integration of short, medium, and long term signals

ghrelin, cholecyskinin, and PYY act as short and medium term signals to influence appetite and energy expenditure. agonists and antagonists of these signals may be developed as potential drugs for weight control


leptin resistance

in most obese people, the leptin level is high, suggesting that the person is insensitive to leptin. leptin resistance limits the wide use of leptin as a drug to treat obesity


5 main components of energy expenditure

1. resting energy expenditure, or BMR
2. energy expended in digesting, metabolizing, and storing food
3. volitional exercise: mechanical work and thermal effect
4. nonexercise activity thermogenesis
5. adaptive thermogenesis


adaptive thermogenesis

facultative. shivering in response to cold exposure. non-shivering is subject to regulating by brown fat tissue


white fat cells

for fat storage and body insulation


brown fat cells

for heat production. rich in mitochondria and express high levels of uncoupling protein, UCP1.


beige fat cells

white adipose tissue that has been partially converted to brown fat. increased number of mitochondria and UCP1



dissipates energy during thermogenesis in brown fat tissue. leaks protons of the electrochemical gradient without being coupled to ATP production. process is called adaptive thermogenesis, or non-shivering thermogenesis. the energy is released as heat without being coupled to ATP synthesis


uncoupling proteins

BAT presence inversely correlates with BMI. UCP1 promotes re entry of protons into mitochondrial matrix, generating heat. fatty acid-proton symporter is activated by fatty acids. UCP1 expression can be controlled in many ways


polygenic inheritance of tendency to obesity

40-70% of body variation is due to genetic factors. a few families with defects in leptin, leptin receptor, and MC4R receptor identified. no common mutations identified yet.



weight loss drug approved by the FDA. combination of naltrexone and bupropion, two drugs used to treat alcohol and drug addiction and depression