so we've all heard of the solution to this problem by simulating gravity through centrifugal force, but has anyone considered perhaps maybe there is simply a way in theory (as yet undiscovered) to prevent the body from shedding bone and muscle mass through medicine? perhaps there is a chemical agent that can be taken to trick the body into not shedding bone and muscle, or a way to alter the gene in the DNA (if its genetic) that tells the body to respond to a low gravity environment in the manner of "hey i dont need so much bone and muscle anymore, let me loosen my grip on it". is there any research into this, or is it even feasible theoretically?

How about making a garment out of a semi-rigid material that restricts movement, so the body will have to work against it to move freely, thus keeping the muscles active...?

that doesn`t help the internal organs and bloodflow much or bone density in non weight bearing structures.

If you take away resistance, atrophy follows.

What about a higher-pressure atmosphere?

It is due to the evolved nature of humans. The body measures stresses on it and strengthens the appropriate parts. Trees do a similar thing, where they strengthen the parts that get stressed the most. Interfering with this process is likely to be incredibly difficult, on par with eg curing aging.