Appetite Regulation and Obesity Flashcards
Homeostatic controls
- like a feedback regulated thermometer
- include:
hypothalamus, brainstem, and nucleus solitary track - hormones (leptin, CCK, GLP-1) work through this regulated system
Hedonic Feeding
- not really regulated and responds to reward or other environmental stimuli
- includes:
parts of the brain like the cortex and nucleus accumbens
AgRP/NPY neurons
- inhibited by leptin and insulin
- increase appetite (ghrelin increases NPY to increase appetite)
- decrease energy expenditure
POMC/CART neurons
- have opposite effect of AgRP/NPY
- decrease ghrelin
- stimulated by leptin and insulin
DECREASE appetite
INCREAE energy expenditure
Satiety
the feeling of fullness that persists after eating and suppress further consumption
Satiation
the process that causes one to stop eating
Ghrelin (function)
high at start of a meal, but rapidly declines after food intake
Leptin (function)
- influences appetite center in hypothalamus
- low leptin levels decreases sensitivity to satiation signals
- high leptin levels means you’ll feel full when you’re supposed to
CCK (function)
- responsive to fat and protein intake
- rapidly reduces meal size and duration
PYY (function)
- responsive to fat intake
- decreases food intake by 30%
High ghrelin levels
Grhelin levels increase as a way for you to eat and gain weight
Low ghrelin levels
- typically low in obese people because they are trying to drive down intake and regulate body weight
Leptin Discovery
- discovered leptin was the hormone missing from ob/ob mice, and the db/db mouse had enough leptin, but was resistant to it
- humans who are obese are leptin deficient
- leptin will not cure obesity unless that person can’t produce leptin
Adipokine
- any hormone that is released in response to how much fat tissue you have and is released from fat cells
- Examples: leptin, insulin, and adiponectin
How is obesity defined?
BMI cut-offs
Evidence obesity is caused partly by genetics
Twin studies where twins have similar body sizes
- BMI and fat distribution were similar
Genes associated with obesity
- Leptin, Leptin receptor, MC4R, POMC
- FTO related to common obesity
Environmental changes that contribute to increases in obesity
smoking, diet, physical activity, toxins, intrauterine conditions, and stress
Why is obesity associated with so many metabolic diseases?
- it promotes an inflammatory response
- when cells get too big they release cytokines (Ex: tnf-alpha)
- results in insulin resistance (starts in muscles and then fat cells)
