I was thinking about how an MRI uses a strong magnetic field to align the spins of hydrogen atoms in the body. What I was wondering about was if the human body experienced a magnetic field much stronger than that from an MRI, is it possible or plausible that a greater portion of the hydrogen atoms in the body could become aligned or that they could stay aligned for a longer period of time? So that someone could become magnetized (or spin polarized) enough to attract magnets or for a significant amount of time, like a few minutes.
You have the mindset of a scientist.
Other scientists have had the same hypothesis as you do. In 2000, Andre Geim put it to test:
The image of a high-temperature superconductor levitating above a magnet in fog of liquid nitrogen can hardly surprise anyone these days – it has become common knowledge that superconductors are ideal diamagnetics and magnetic field must expel them. On the other hand, the enclosed photographs of water and a frog hovering inside a magnet (not on board a spacecraft) are somewhat counterintuitive and will probably take many people (even physicists) by surprise.
This is the first observation of magnetic levitation of living organisms as well as the first images of diamagnetics levitated in a normal, room-temperature environment (if we disregard the tale about Flying Coffin of Mohammed as such evidence, of course). In fact, it is possible to levitate magnetically every material and every living creature on the earth due to the always present molecular magnetism. The molecular magnetism is very weak (millions times weaker than ferromagnetism) and usually remains unnoticed in everyday life, thereby producing the wrong impression that materials around us are mainly nonmagnetic. But they are all magnetic. It is just that magnetic fields required to levitate all these "nonmagnetic" materials have to be approximately 100 times larger than for the case of, say, superconductors.
It may take quite the force to levitate a person:
our frog levitated in fields comparable to those used in commercial in-vivo imaging systems (currently up to 10T).
Electromagnetism is not my forte, but if it takes an MRI machine to levitate a frog, I think it might take something between the size of a room and the size of a multistory building to impress a perceptible pull on an adult human.
Seems like It wouldn't harm you, though:
In the case of living organisms, no adverse effects of strong static magnetic fields are known (...). The small frog looked comfortable inside the magnet and, afterwards, happily joined its fellow frogs in a biology department.
This work has won Geim a very distinguished prize, making him the only person ever to individually win both a Nobel and an Ig Nobel - the latter from the very levitating frog experiment.