Food intake and Energy Expenditure

Lecture 2 & 3: What makes us decrease and increase feeding behavior

Homeostasis

Maintains the internal environment within narrow physiological range

Energy intake vs Energy Expenditure is equal

Not as realistic in today’s sedentary society (in the US)

Three components of neuronal response of homeostasis

• Humoral

• Visceromotor

• Somatic

Role of Hypothalamus

• regulates homeostasis

Humoral Response

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Roles of Oxytocin on the boday/brain

• facilitates bonding

• reduces anxiety

• rewards caloric intake

News and Views

study of oxytocin and intake of food in men

context dependent

• resting state

• food is chosen

Glucose

our body’s energy “cash”

• instant supply of energy needs

• via food or produced by liver

Glycogen

our body’s “standby reserve” of energy

• we break down glycogen when glucose runs low

Fat

our body’s 3rd reserve of energy and “certificate of deposit”

• fat forms into triglycerides and energy

Well-fed state vs Fasting state

• know briefly, not in detail

Process of High Blood Sugar to Low

know well

1. High Blood Sugar

   1. promotes insulin release

Process of low blood sugar to high

know well

1. Low blood sugar

   1. promotes glucagon release

2. Pancreas

3. Glucagon

   1. simulates glycogen breakdown

   2. Glucose → Liver → Glycogen

4. Raises blood sugar

Type 1 Diabetes

Autoimmune Disease

• body attacks itself, destroying beta cells as it recognizes it as a foreign body

• you don’t produce insulin, which is necessary for body to use glucose for energy

• No glucose regulation

  • issues - brain problems, energy

Type 2 Diabetes

Insulin Resistance: Tissues cannot respond to insulin

• Glucose stays in the blood

• No glucose regulation

  • issues: hard on cells

    • osmotic water loss

    • damage of blood vessels

Controlling glucose levels

• diet

• exercise

Lipid levels: Adipose Tissue

releases leptin

Satiety

being satisfied and not having hunger or motivation to seek out food

Catabolic Factors do what

• Decrease appetite

• Decrease food intake

• Increase metabolism

Anabolic factors do what

• Increase appetite

• Increase food intake

• Decrease metabolism

Hunger Homeostatic feedback loops

• Short-term feeding behavior: Maintenance of blood glucose levels

• Long-term feeding behavior: Maintenance of fat stores

hunger can also be affected by mood

Long-term feeding behavior goal

• Maintain long-term energy stores (fat)

  • fat have 2x energy as glucose, doesn’t require excess water storage like glucose

  • body has set-point for amt of fat

Role of set-point in the body

rat study: fasting and overfeeding resulted in same weight

reality show: guy went from 444-289lbs back to 450

• Lipostatic Hypothesis

Lipostatic Hypothesis

states that the brain monitors fat levels and maintains them at some fixed set-point amount

• which requires the fat communicates with the brain in some way

a theory suggested a blood-borne hormone played a role

• Evidence: 1960s study of Parabiosis

  • fused two animals to share the same blood

    • genetically obese mouse and normal mouse

  • 1994: Discovered presence of hormone: Leptin

    • mutation of OB: recessive mutation that causes weight gain

      • reduced and didn’t produce leptin

    • injected obese mice with leptin: restored normal weight

Leptin

suppresses hunger and feeding, increased energy expenditure, reproductive competence

• “Starvation signal”

• lowers amount of food intake

• lowers amount of body fat

what is leptin deficiency?

How brain controls/detects leptin levels

• Leptin theorized that leptin effects hypothalamus

• Known: leptin activates a-MSH and CART in arcuate nucleus of hypothalamus

What happens when there’s excess adipose tissue (Humoral, visce., Somatic)

Integrated response

• Humoral: high secretion of TSH and ACTH, raises metabolic rate of cells in body

• Visceromotor: higher activity of sympathetic response, raises metabolic rate and body temperature

• Somatic motor: decrease in feedin behavior

Where in the brain is leptin binding to coordinate this response that will eventually reduce adipose tissue?

Arcuate Nucleus

Function of Arcuate Nucleus

• makes a-MSH and CART