What causes bread to go stale so quickly?

Bread goes stale primarily due to a process called starch retrogradation. When bread is baked, starch granules absorb water and swell in a process called gelatinization. As the bread cools and ages, those starch molecules gradually recrystallize and expel moisture, causing the crumb to become firm and dry. This happens fastest at refrigerator temperatures, which is why refrigerating bread actually speeds up staleness rather than preventing it. Moisture loss to the surrounding air also plays a role, making the crust soft and the interior dry. Bread with higher fat content, like brioche, stales more slowly because fat interferes with starch recrystallization. Freezing bread stops retrogradation almost entirely, making it the best storage method for longer-term freshness.