Welcome to the comprehensive, medically reviewed A-to-Z Autophagy & Intermittent Fasting Glossary. Use this reference guide to understand key biochemical terms, cellular mechanisms, and metabolic markers associated with time-restricted eating.
A – D
Akkermansia muciniphila: A beneficial gut bacterium that feeds on and strengthens the gut mucosal barrier. Intermittent fasting significantly increases Akkermansia levels.
AMPK (AMP-Activated Protein Kinase): The master energy sensor of the cell. Activated during fasting when cellular energy is depleted, AMPK shuts off fat storage and stimulates autophagy.
Autophagosome: A spherical double-membrane vesicle that engulfs damaged cellular organelles and delivers them to the lysosome for degradation.
Autophagy: The body’s natural cellular recycling system (literally “self-eating”) that cleans out damaged intracellular debris and senescent proteins.
BDNF (Brain-Derived Neurotrophic Factor): A neurotrophic protein that stimulates the growth of new brain neurons and synapses, elevated during intermittent fasting.
Beta-Hydroxybutyrate (BHB): The primary ketone body produced by the liver during fasting and ketosis, serving as an ultra-clean fuel source for the brain and heart.
BMR (Basal Metabolic Rate): The minimum number of calories your body burns at complete rest to maintain vital life functions (calculate your BMR).
E – M
Early Time-Restricted Feeding (eTRF): A fasting schedule where the eating window is placed in the early morning and afternoon (e.g., 8 AM to 4 PM), matching circadian insulin sensitivity.
Electrolytes: Essential minerals—primarily Sodium, Potassium, and Magnesium—that regulate nerve impulses, hydration, and fluid balance inside cells.
Ghrelin: The “hunger hormone” secreted by the stomach. Ghrelin peaks in rhythmic waves at habitual meal times and declines naturally after 20–30 minutes.
Glycogen: The stored form of glucose in the liver and skeletal muscle. Fasting depletes glycogen within 12–16 hours, prompting the switch to fat burning.
HGH (Human Growth Hormone): An anabolic hormone that spikes up to 500% during fasting, protecting muscle tissue from breakdown while burning fat.
Ketosis: A metabolic state where the liver breaks down fatty acids into ketone bodies to use as the primary fuel source instead of glucose.
Lipolysis: The biological breakdown of triglycerides stored in adipose fat cells into glycerol and free fatty acids for energy.
Mitophagy: A specialized sub-pathway of autophagy specifically dedicated to degrading and recycling damaged, defective mitochondria.
MMC (Migrating Motor Complex): An electromechanical wave of digestive tract contractions that sweeps undigested food and bacteria from the small intestine during fasting.
mTOR: The master growth regulator of cells. Activated by protein and carbs, mTOR stimulates cell growth but directly inhibits autophagy.
N – Z
NEAT (Non-Exercise Activity Thermogenesis): Calories burned through daily spontaneous movement such as walking, fidgeting, and standing.
OMAD (One Meal a Day): A 23:1 fasting protocol where all daily calories are consumed within a 1-hour window (read OMAD guide).
Refeeding: The process of reintroducing calories after a fast. Doing so with gentle, non-glycemic whole foods prevents digestive distress.
TDEE (Total Daily Energy Expenditure): The total number of calories your body burns per 24 hours (calculate your TDEE).
Telogen Effluvium: A temporary hair shedding condition caused by extreme caloric restriction, preventable by maintaining adequate protein intake.
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