Hunger

Reading Quiz

• What is the function of ghrelin?

I. Physiological Influences

A. HomeostasisB. Glucose (blood sugar)

1. Increased level of a hormone (__?__) diminishes blood sugar

2. Hunger increases when blood glucose level drops

C. Hypothalamus1. 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 InfluencesA. 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• https://www.youtube.com/watch?v=yErb0jzIPL8

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?

ObesityA. Genetic influences

1. Evolution of thrifty genes2. Body weight regulation vary among individual’s

tendency to become obese

B. Fat cells1. fat cells increase, rarely decreases2. Causes of increase

a. early childhood eating patternsb. 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. media3. abundance in high calorie food

http://www.youtube.com/watch?v=N2diPZOtty0

http://www.youtube.com/watch?v=B-tv7iUsb4I

Eating disorders

A. Anorexia nervosa1. Diagnosis based on

a. Significantly underweight (below 85% normal)

b. Distorted view of body size/shape

c. Fear of gaining weightd. Menstruation stops in

post-pubertal females

2. Predisposing or maintaining factors

a. genetic influencesb. 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 ona. Repeated episodes of overeating, followed by

vomiting, laxative use, and/or excessive exerciseb. Undue concern with body size or shape

2. Predisposing or maintaining factorsa. Geneticb. Culturalc. 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…