3.1 primary motives HUNGER

3.1 primary motives

HUNGER

• prevents energetic deficits

• maintain body weight

Two models of hunger

• Short-term appetite (glucostatic hypothesis).

• Long-term energy balance (Lipostatic hypothesis)

Glucostatic hypothesis - short-term appetite

• Accounts for the onset & termination of hunger & eating.

• short-term hunger cues regulate the initiation of meals, their size & termination.

• The glucostatic hypothesis states that blood-sugar levels are critical to hunger (low bloodsugar - people feel hungry)

PHYSIOLOGY OF HUNGER (two types)

• SATIETY

• HUNGER

What brain structure regulates hunger & satiety

The hypothalamus — specifically, the lateral hypothalamus & ventromedial hypothalamus.

What is the function of the lateral hypothalamus?

It is the appetite’s drive center — it stimulates hunger when activated.

What is the function of the ventromedial hypothalamus?

It acts as the negative feedback’s appetite center — it signals satiety & stops eating.

lipostatic hypothesis - long-term energy balance 

• stored energy (fat mass) is available & used as a resource to supplement glucose-monitored energy regulation

• fat produce energy

• when the mass of fat stored drops below its homeostatic balance, adipose tissue secretes hormones into the bloodstream to promote weight gain (hormone → ghrelin)

• when the mass of fat stored increases above its homeostatic balance, adipose tissue secretes hormones into the bloodstream to reduce food intake & promote weight loss motivation (hormone → leptin).

when the mass of fat stored drops below its homeostatic balance

• adipose tissue secretes hormones into the bloodstream to promote weight gain

• (hormone → ghrelin)

when the mass of fat stored increases above its homeostatic balance

• adipose tissue secretes hormones into the bloodstream to reduce food intake & promote weight loss motivation

• (hormone → leptin).

Which physiological factors influence the hypothalamus in regulating hunger?

• Liver (glucose levels)

• Stomach dimensions (fullness)

• Body temperature

What happens when glucose levels in the liver are low?

• The lateral hypothalamus is activated, triggering feelings of hunger.

What happens when the stomach is full & glucose levels rise?

• The ventromedial hypothalamus is activated, producing satiety signals.

How does body temperature affect hunger?

• Lower body temperature tends to increase hunger,

• while higher body temperature decreases hunger.

What are the two opposing centers in the hypothalamus controlling hunger & satiety?

• Lateral hypothalamus – hunger center (LH)

• Ventromedial hypothalamus – satiety center (VMH)

Set point theory

• body defends a fixed weight

• linked to physiology, genetics & molecular biology.

• adipose tissue intake & expenditure via a set point encoded in the brain

• consistent with biological factors & energy balance

if the set point changes in response to social influence on obesity

• not a set point 

Settling point theory

• linked to psychology & nutrition 

• replace the set point 

• focus → human behaviour & environment 

Settling point theory → body weight

• influenced by a variety of factors

• settles based on the interaction between biological, environmental & behavioural influence

food available settling point theory

• we have low expenditure.

• our body fat settles at a higher point.

Environmental influences affect eating behaviour

• time of day

• stress

• sight

• smell

• appearance

• taste of food

Eating behavior increases when 

• There is a variety of foods/flavours

• large portions 

• are in the presence of others 

Restraint-release situations of hunger

• Dieting & fasting can interfere with physiological guides.

Dieting

• Individual brings eating behaviour under cognitive rather than under physiological control

• dieting causes subsequent bingeing.

Counterregulation

• a paradoxical pattern displayed by dieters

• eat very little when just nibbling but eat very much after consuming a large, high-calorie “preload”

Binge-eating leads to 

• Conditions that threaten ego

• High-calorie food

• Alcohol

• Anxiety & depression

Cycle of binge eating / diet - illustration

WHO - overweight + obesity

• abnormal excessive accumulation of fat that can harm health

• obesity has tripled since 1975

overweight - BMI

by a body mass index greater than equal to 25 and obesity by a BMI greater than or equal to 30.

how to prevent overweight

• Decrease eating through self-regulation strategies.

• Exercise motivation (increasing physical activity to expend fat stores).

• Mindfulness over one’s environmental influences.