BIOPSYCHOLOGY OF MOTIVATION

Hunger, Eating, and Health

Why do many people eat to much?

Reasons why People EAT

• Survival• Pleasure• Serious personal and Health problems

EXCESSIVE EATING ......

• DIABETES• HYPERTENSION• CARDIOVASCULAR• CANCER

Contrast..............AnorexiaBulimia

• We are full if we reach the optimal level or SET POINT

What is hunger?

• Motivation to eat...Reading the case of “Man Who Forgot Not to Eat”

Purpose of Hunger----- to increase the probability of eating and the primary purpose of eating is to supply the body with the molecular building blocks and energy it needs to survive and function (Blackburn 2001)

Mechanism of Eating

Digestion

• The gastrointestinal process of breaking down the food and absorbing its constituents into the body.

OUTPUT: Energy

• 3 forms 1.Lipids ----fats2.Amino acids – proteins3.Glucose-carbohydrates------starches and

sugars

Storing of Energy

• 3 forms1.Fats2.Glycogen3.Proteins-------consequences in the amt. Of stored fat

• Glycogen----largely stored in the liver and musclesGlucose- the body main directly utilizable source of

energy.Why body preferred fat instead of glycogen1. The gram of fat can store almost twice as much energy2. The glycogen unlike fat attracts and holds substantial

quantities of water.Note: if fat were stored as glycogen , we will weigh over

275kilograms/ 600pds

3 PHASES OF ENERGY METABOLISM

Energy metabolism- the chemical changes by which energy is made available for an organism’s use)

1.CEPHALIC PHASE – The preparatory phase ----often begins with the sight, smell, or even just the thought of food and ends when the food starts to be absorbed into the bloodstream.

2. ABSORPTIVE PHASE- the period during which the energy absorbed into the bloodstream from the meal is meeting the body’s immediate energy needs.

3. FASTING PHASE-the period during which all of the unstored energy from the previous meal has been used and the body is withdrawing energy from its reserves to meet its immediate energy requirementd; it ends with the beginning of the next cephalic phase.

• During the periods of rapid weight gain-----people go directly from one absorptive phase into the next cephalic phase------without experiencing an interviewing fasting phase.

2 pancreatic hormones

• Insulin• GlucagonInsulin Functions:1.It promotes the use of glucose as the primary

source of energy by the body2.It promotes the conversion of bloodborne

fuels to forms that can be stored; glucose to glycogen and fat and amino acids to protiens.

• 3. it promotes the storage of glycogen in liver and muscle; fat in adipose tissue and proteins in muscle.

The phases are characterized by high blood levels of glucagon and low levels of insulin.

WHAT HAPPEN WITHOUT THE HIGH LEVELS OF INSULIN IN PROCESS?

ANSWER

• The glucose has difficulty entering most body cells; ; thus glucose stops being the body’s primary fuel.

• The conversion of protein to glucose is called GLUCONEOGENESIS

While the glucagon in the fasting phase promote the release of free fatty acids from adipose tissue and becomes the body’s primary fuel.

• There is also the conversion of free fatty acids to ketones which are used by the muscles-----source of energy during the fasting phase.

What happen if we dont eat for an hour?

ANSWER

• The brain will starts to use ketones

THEORIES OF HUNGER and EATING

Set points vs Positive incentivesSet Point AssumptionIt is when the energy resources of the body are

returned to their optimal level.------when to eat again?When the level of the body’s energy resources

falls far enough below the set point, a person becomes motivated by hunger to initiate another meal.

• The meal continues, acdg. To the set-point assumption, until the energy level returns to its set point and the person feels satiated ( no longer hungry).

Further,ASSIUME that hunger and eating work in much

the same way as a thermostat regulated heating system in a cool climate.

3 components of set-point systems

• Set point mechanism• Detector mechanism• Effector mechanism

-defines the set pt.-detects deviations from the set point-acts to eliminate the deviations--------------are

the thermostat.

Negative feedback systems

• Explain the process of Negative feedback systems?

GLUCOSTATIC AND LIPOSTATIC SET-POINT THEORIES OF HUNGER

AND EATING• RESEARCHER-EATING is regulated by a system that is

designed to maintain a blood glucose set point.

The idea -----we become hungry when our blood glucose levels drop significantly below their set point and that we become satiated when eating returns our blood glucose levels to their set point. GLUCOSTATIC THEORY

• THE PURPOSE OF EATING ---- is to defend a blood glucose set point, bec. Glucose is the brains primary fuel.

• LIPOSTATIC THEORY – another set-point theory that was proposed in various forms in the 1940 and 1950s.

• Acdg--- every person has a set point for body fat, and deviations from this set point produce compensatory adjustments in the level of eating that return levels of body fat to their set point.

What are the problems with Set-Point theories of hunger and

eating• Survival• Evidence• Deficient -----did not considered taste,

learning and social influences

Positive-Incentive Theory

• Anticipated pleasure of eating-----called positive incentive value

Factors that determine What/when/how much We Eat

• Taste preferences and aversion• Learning to eat vitamins and minerals• Premeal hunger• Conditioning• Satiety signals• Sham eating

• Appetizer Effect and satiety• Serving Size and Satiety• Social influences and satiety• Sensory-specific satiety

Brain

• Two different regions1.Ventromedial hypothalamusa. Hyperphasia- excessive eatingb. Extreme obesity in ratsTWO DIFFERENT PHASESA.Dynamic-after operation, excessive eating &

weight gainB.Static-stable

• Lateral hypothalamusa. Aphagia- a complete cessation of eating----

accompanied by adipsia- a complete cessation of drinking.

What CCK?

Prader-Willi Syndrome: patients with insatiable hunger

• Results from an accident of chromosomal replication, experience insatiable hunger, little or no satiety and an exceptionally slow metabolism

REGULATION OF BODY WEIGHT BY CHANGES IN THE EFFICIENCY OF ENERGY

UTILIZATION• Diet induced thermogenesis- the mechanism

by which the body adjust the efficiency of its energy utilization in response to its levels of body fat.

• Basal metabolic rate- the rate at which energy is utilized to maintain bodily processes when resting.

OBESITY/ANOREXIA and BULIMIA NERVOSA

• Serotogenic agonists reduce food consumption • ANOREXIA NERVOSA- disorder of

underconsumption• BULIMIA NERVOSA- periods of not eating

interrupted by bingeing and purging.

ANOREXIA treatment of .....

• Bradycardia-slow heart rate• Hypotension- low blood pressure• Hypothermia- low body temperature• Anemia- deficiency of red blood cells

BULIMIA treatment for.....

• Irritation and inflammation of the esophagus, vitamin and mineral deficiency, electrolyte imbalance, dehydration and acid reflux.