Why we cook food in oil

Dietary fats are important because they dissolve and transport fat‑soluble vitamins (A, D, E, K), enabling those nutrients to be absorbed in the intestines.

Oiling before oven roasting often matters less because convective oven heat and the food's own rendered fat can redistribute over surfaces and promote browning without the direct, localized contact dynamics of a hot pan.

Fattier cuts or skin-on pieces can self-baste because rendered fat melts and collects in the pan, coating surfaces so the meat effectively fries in its own fat as cooking proceeds.

Non-stick pans reduce adhesion but can worsen uneven cooking because steam bubbles can lift food away from the surface, interrupting sustained contact and producing gray, underbrowned patches instead of a continuous crust.

Fat prevents sticking both by physically separating proteins from the pan and by acting as an effective thermal interface that cooks the surface faster so a brown crust forms and lifts more easily.

Proteins stick to hot metal because they denature at high temperature and can form chemical bonds or complexes with the metal surface, anchoring the protein until enough browning and rigidity allows release.

Water can serve as a thermal interface but is worse for sautéing because it boils at 212°F (100°C) and escapes as steam before reaching the ~330°F needed for Maillard browning, and its low viscosity prevents it from coating food effectively.

Cooking without oil produces highly localized browning and much slower overall cooking because only the tiny points touching the metal get efficient heat transfer, so those spots can burn while most of the food stays cooler.