Lecture Notes: Fed vs. Fasted State

Key Terminology

• Fed State (Absorptive State):
  • Occurs up to 4 hours after eating
  • Characterized by nutrient absorption
  • Dominated by insulin
• Fasted State (Post-Absorptive State):
  • Occurs when you haven't eaten for a few hours
  • Dominated by glucagon

The Fed State

• Insulin's Role:

  • Lowers blood glucose
  • Anabolic storage hormone
  • Involves fat storage, amino acid storage, and synthesis

• Processes in Key Organs:

  • Liver:
    • Converts excess glucose into glycogen (storage form of carbohydrate)
    • Potential conversion of amino acids into ketones (especially on a high protein diet)
  • Muscles:
    • Takes in glucose for fuel and stores some as glycogen
    • Absorbs amino acids for muscle building
  • Adipose (Fat) Cells:
    • Takes in excess energy and stores it as fat

The Fasted State

• Glucagon's Role:

  • Keeps blood glucose levels up
  • Dominates when blood glucose levels fall

• Processes in Key Organs:

  • Liver:
    • Converts stored glycogen back to glucose
    • Uses ketones for fuel if needed
  • Muscles:
    • Converts stored glycogen back to glucose for fuel
    • Can break down proteins for fuel if necessary
  • Adipose (Fat) Cells:
    • Releases stored fat for oxidation (beta oxidation to generate ATP)
    • Can use fat to produce ketones

Conclusion

• The body's state (fed or fasted) determines metabolic processes
• Continuous energy supply is crucial for cellular function
• Metabolic processes are essential for life, relying on ATP production