Hunger

Reading Quiz What is the function of ghrelin?

I. Physiological Influences A.Homeostasis B.Glucose (blood sugar) 1.Increased level of a hormone (__?__) diminishes blood sugar 2.Hunger increases when blood glucose level drops C.Hypothalamus 1. Regulates hunger, thirst, and sex

What happens if you lesion the VMH?

LH and VMH Dual Centers criticisms Not simply on-off switches –LH and VMH are elements, but not the elements Modulation of hunger today comes from the arcuate/paraventricular nucleus –Arcuate nucleus SUPER sensitive to incoming hunger signals and satiety signals

Glucose and digestion Food taken in by body is converted to glucose Glucostatic Theory: arcuate nucleus monitors glucose fluctuation which contributes to modulation of eating

Conclusion Does the stomach regulate hunger? HELL TO THE NO. Period.

What regulates hunger? Insulin –Secreted by pancreas (which system in the body is that?) function: to break down glucose to be absorbed in blood stream for energy –Inadequate supply of insulin = diabetes Type 1 = little or no insulin secretion Type 2 = resistant to insulin action Insulin levels increase when people eat Insulin secretion plays role in determination of hunger –Hypoglycemic – not enough glucose –Hyperglycemic – too much glucose

2 other hunger related hormones Ghrelin – causes stomach contractions and promotes hunger –After food consumption, upper intestines release hormone CCK = satiety signals to the brain Think Louis C.K….

“The meal is not over when I’m full. The meal is over when I hate myself…”

Other hormones Leptin –Secreted by fat cells; when abundant, causes brain to increase metabolism and decrease hunger Orexin –Hunger triggering hormone Obestatin –Secreted by stomach – send “I’m full” signals PYY –Digestive tract hormone – sends “I’m not hungry” signals

Putting it all together Where do leptin, ghrelin, CCK, and insulin converge? Stomach or hypothalamus? Hunger happens in so many places – neural circuits, neurotransmitters, digestive processes, hormonal fluctuations –All in all – it’s a decentralized mess How can you then link that to body weight fluctuations and regulation of diet? Why is there no one cure for mass increase in weight?

II. Sensory Influences A.Taste, smell, mouth feel, and sight all influence wanting and liking B. Sweet taste can stimulate appetite by triggering release of __?__, causing a drop in blood ___?___ C. Wanting and liking of most foods is based on experience Preference based on consequences of eating (nutrition, nausea, etc) Have you ever eaten something so much that you, to this day, never want to eat it again?

III. Socio-cultural influences A.People eat more when in a group than alone (social coaction) True for western women? Roles of femininity B. Family and cultural practices related to eating and meal customs –“CLEAN YOUR PLATE, MISTER!”

C. Cultures have rules about appropriate occasion of eating –i.e. birthday cake, insects taboo or delicacy?

Obesity A.Genetic influences 1.Evolution of thrifty genes 2.Body weight regulation vary among individual’s tendency to become obese

B. Fat cells 1. fat cells increase, rarely decreases 2. Causes of increase a. early childhood eating patterns b. adult overeating 3. Weight-loss diets shrink fat cells, but does not destroy them

Set point theory C. Set point 1. The particular level of weight the body strives to maintain 2. Obese people’s set points are higher than average range What are the two hypothalamic nuclei that make up set-point theory?

D. Metabolism – rate of expenditure 1. varies among individuals (two people can eat the same and have different weights) 2. diets cause lower metabolic rate, making it harder to lose weight - how should you diet then?

E. Socio-cultural influences on obesity 1. parents using food as reward 2. media 3. abundance in high calorie food

Eating disorders A.Anorexia nervosa 1.Diagnosis based on a.Significantly underweight (below 85% normal) b.Distorted view of body size/shape c.Fear of gaining weight d.Menstruation stops in post-pubertal females

2. Predisposing or maintaining factors a. genetic influences b. cultural influences - objectification theory: women and girls tend to acculturate body image to outside expectation - African American girls report more positive body images than white or Latina girls

c. Preference for thinness in sports (ideal body size)

B. Bulimia nervosa 1.Diagnosis based on a.Repeated episodes of overeating, followed by vomiting, laxative use, and/or excessive exercise b.Undue concern with body size or shape 2.Predisposing or maintaining factors a.Genetic b.Cultural c.behavioral

C. Methodological Considerations 1.When people who are obese or have an eating disorder are compared to those who do not, distinguishing what causes the problem from having the problem can be difficult. Just having the problem changes thoughts, feelings, and behavior “Why don’t you just eat less/more? Duh…” Way off…