You already know which oil is worse. Palm oil sits in the bad column, olive oil in the good one, and the sorting happened so long ago you can't remember who taught you. The ranking is correct. The reason you believe it is wrong.
Most people frame palm oil vs olive oil as a cholesterol story. Saturated fat raises LDL, unsaturated fat doesn't, end of conversation. The actual answer lives somewhere nobody thought to look: inside the body, measured by imaging, where the same surplus calories built completely different bodies depending on which fat delivered them.
Does Palm Oil Cause More Fat Gain Than Olive Oil?
A double-blind trial overfed two groups by 750 calories a day for seven weeks. One group ate the surplus from palm oil. The other from polyunsaturated fat. Both groups gained 1.6 kg on the scale, identical.
Imaging caught what the scale missed.
The palm oil surplus built four parts fat for every one part lean tissue. A 1:4 ratio. The polyunsaturated surplus built equal parts, 1:1. Same calories. Same weight. Completely different distribution underneath the skin.
The palm oil surplus packed twice as much visceral fat into organ spaces. The polyunsaturated surplus built three times more lean tissue instead. The scale measured nothing that mattered.
Palm oil surplus drove a 1:4 fat-to-lean ratio while polyunsaturated fat surplus drove 1:1, despite identical weight gain. The mechanism is saturated fat content driving ectopic fat storage. Palm oil (~50% SFA) triggers this pathway; olive oil (~14% SFA) does not carry enough. Lean tissue advantage held only in lean adults.
— Rosqvist et al. 2014 · Diabetes · n=39 · Double-blind RCT with MRI
Here is where the answer gets honest. The comparison was palm oil against sunflower oil, not olive oil. Nobody has tested palm oil and olive oil head-to-head with body-composition imaging. The mechanism, though, points in one direction: palm oil is roughly 50% saturated fat. Olive oil is about 14%. The pathway that drove ectopic fat storage activated in response to the saturated fat load. Olive oil doesn't carry enough to trigger the same response.
One more layer before the binary settles. In overweight adults, the liver fat effect held. The lean tissue advantage disappeared. Three times more muscle from polyunsaturated fat was real only in people who were already lean. If you're carrying extra weight, the body-composition divergence narrows. The full evidence on how fat type reshapes body composition shows which effects held across populations and which ones didn't.
The binary you started with was never wrong. Palm oil IS worse for body composition. The reason was never cholesterol. It was where the surplus physically ended up.