Hunger isn’t just about an empty stomach. Your brain receives signals from body composition, hormones, emotions, and even gut microbes. Here’s how the three major types work:

1️⃣ Homeostatic Hunger (Energy Balance Hunger)
This is your body’s “fuel gauge.” It rises and falls based on energy needs and metabolic signals.
What drives it: Ghrelin from the stomach stimulates hunger; leptin from fat cells and incretin hormones (GLP-1, PYY, CCK) reduce it.

What it does: Ensures your intake matches your energy needs for exercise, growth, and tissue repair.

🟢 Example: After a long run, homeostatic hunger pushes you to replace calories and glycogen.

2️⃣ Hedonic Hunger (Reward-Driven Hunger)
This is your “food pleasure” system. It’s triggered by sight, smell, habits, and emotions, not by actual energy needs.
What drives it: Brain reward circuits activated by highly palatable foods (sugar, fat, salt).

What it does: Encourages eating even when you’re not truly hungry. Weak satiety signals make it harder to stop.

🟢 Example: Craving dessert after dinner even though you’re full.

3️⃣ Microbiota-Driven Hunger (Gut Microbe Hunger)
Your gut bacteria also shape hunger signals by producing metabolites that influence hormones and the brain.

What drives it: Microbes generate compounds that mimic hunger or satiety signals, affect insulin, and modulate ghrelin, GLP-1, and PYY.

What it does: Links gut health to appetite regulation and metabolic control.

🟢 Example: Certain bacterial imbalances may increase cravings or weaken satiety, nudging overeating.