Food addiction

Question 1

Why do we eat? what are the mediating factors?

Answer 1

Homeostasis (energy demands) 
Emotional state (stress, boredom) 
Hedonism (pleasure) - very similar pathways as drugs 

Simple biological model: hypothalamus, food intake, humoral signals (arising from the body)

Question 2

What are the mechanisms of hunger-stimulating GI peptides?

Answer 2

Ghrelin (stomach/pancreas)

• levels increase before food consumption (will level out/pass if you don’t eat)
• levels are lower in obese individuals
• sleep can influence ghrelin levels
• activates a portion of the DA reward pathway

Question 3

What are hormones behind adiposity signals (satiety)?

Answer 3

Leptin (adipose)
Insulin (pancreas)
Cholecystokinin (CCK) - small intestine

Question 4

What is the mechanism of action for leptin (adipose)?

Answer 4

Mechanism of action for leptin at hypothalamus

• antagonizing the effects of neuropeptide Y (stimulant)
• antagonizing the effects off anandamide
• promote synthesis of a-MSH (appetite suppressant, stimulates satiety)

Question 5

What is the mechanism of action for insulin (pancreas)?

Answer 5

Mechanism of action for insulin

• causes cells to take up glucose from blood
• stops the use of fat as an energy source by inhibiting the release of glucagon
• hen control of insulin levels fails, patients can develop diabetes mellitus

Question 6

What are the cyclical processes of hunger stimulation?

Answer 6

Ghrelin - pre-prandial rise, orexigenic agent, stimulates eating
Leptin - postprandial rise, anorexigenic agent, inhibits eating

Question 7

How did they discover the necessity of hypothalamus in hunger signals?

Answer 7

Study - mice were very obese (Jackson laboratory 1950)

Helped in the discovery of leptin (administration of leptin reduced weight gain effects)

Question 8

What is the dual-center hypothesis with the hypothalamus and hunger?

Answer 8

Two distinct regions
- ventromedial hypothalamus: eating (off), humoral signals, hunger
- lateral hypothalamus: eating (on), humoral signals
Each region regulates the opposing action
- hunger vs. satiety

Question 9

What three factors lead to overeating? what changes have occurred to consumption over time?

Answer 9

Disrupted neurobiology
Poor impulse control
Environmental factors

Personal food consumption has increased
- serving size, food access, social context, stress

Question 10

Describe two studies that show human eating habits in different contexts?

Answer 10

Popcorn study

• people eat more fresh and stale popcorn from a large box than from a medium box (eat 100% or medium box, and 150% of large box)
• if it is there, we will eat it (does not matter if it is stale)

Candy study
- people eat more candy when it is visible than when it is covered (both proximally and distally)

Question 11

What are the levels of activity used to determine caloric intake?

Answer 11

Sedentary - little or no physical activity
Low active - daily routine and leisure time has some limited physical activity
Active - at least 2.5 hours of moderate to vigorous activity per week

Question 12

What is obesity? (BMI) what are the stats?

Answer 12

A metabolic state where excess fat accumulates in peripheral tissues including (adipose, muscle, liver)
Body mass index (BMI) > 30
Forbes (Canada) - 14.3%, ranks 35 on a 2007 list of overweight countries with a percentage of 61.1% of citizens with an unhealthy weight

Question 13

What are the physiological effects of food consumption?

Answer 13

Similar activation of brain centers in the dopamine-reward pathway
- nucleus accumbent (NA)
- prefrontal cortex (PFC)
- ventral tegmental area (VTA)
- amygdala
Bold fMRI - functional imaging, shows increase blood flow to DA center
Food consumption is associated with increases in DA levels in the NA
- in food addicts, DA release can be significant

Question 14

What is the model of food addiction? What are the symptoms of food addiction?

Answer 14

Food addiction is associated with an obsessive-compulsive relationship with food

Symptoms include

• frequent periods of uncontrollable binges
• consume food beyond the point of satiety
• feeling of guilt and depression
• excessive time and thought devoted to food
• preoccupation with body weight

Question 15

What are the secondary effects of food addiction? (concurrent disorders, trigger foods)

Answer 15

Can lead to the development of an eating disorder, including

• bulimia disorder
• binge eating disorder

Trigger food can activate the reward centers of the brain and can cause the release of 5-HT (serotonin)
- increased depression and anxiety due to low levels of 5-HT
Abstinence from addictive food and food eating processes causes withdrawal symptoms
- mood swings, agitation, faintness, headaches, dysphoria, hypoglycemia

Question 16

What are the criteria for food addiction?

Answer 16

Criteria: tolerance, withdrawal, investment, social change

Obesity behavior: increased consumption for satiety, depression, dysphoria, time spent eating, costs, fear of rejection