Fasting: the history, pathophysiology and complications.

Area of Science:

• Physiology
• Metabolic Science
• Endocrinology

Background:

• Understanding the physiology of fasting is crucial for therapeutic dietary interventions and managing food deprivation in various diseases.
• Prolonged fasting for political or religious reasons is increasing, necessitating physician awareness.
• Existing research often focuses on obese individuals, with limited applicability to lean populations.

Observation:

• Early in fasting, weight loss is rapid (0.9 kg/day) due to negative sodium balance.
• Metabolically, fasting initially involves high gluconeogenesis using amino acids.
• As fasting progresses, ketosis develops from fatty acid oxidation, with ketones replacing glucose for central nervous system energy.

Findings:

• Hormonal changes during fasting include decreased insulin and T(3), and increased glucagon and reverse T(3).
• Ketone bodies become the primary energy source for the central nervous system, sparing protein.
• Medical complications can arise, including gout, kidney stones, postural hypotension, and cardiac arrhythmias.

Implications:

• Physicians must be prepared to manage patients undergoing prolonged fasting.
• Further research is needed to understand fasting effects in lean individuals.
• Awareness of potential medical complications is vital for patient safety during fasting regimens.