First principles

LDL and HDL aren’t cholesterol

Fat and water don’t mix — so cholesterol and triglycerides can’t just float in the bloodstream. They’re packed into lipoproteins: tiny ships with a fatty cargo inside and a water-friendly shell of protein and phospholipid outside.

So “LDL” and “HDL” are not types of cholesterol — they’re the ships that carry it. LDL ships cholesterol out to the tissues; HDL brings the excess back. Same cargo, opposite direction.

This is the whole reframe: you’re not measuring “good and bad fat” — you’re measuring delivery trucks and return trucks.

A lipoprotein: fatty core, apolipoprotein shell — a cargo ship