Microgravity and How It Interacts With The Body

I was sparked to make this post in response to some revelations I had whilist writing my most controversial post yet, in which I posited that microgravity would almost certainly lead to weight gain if a proper regimen was not adhered to, and I said I would make a post here outlining some of my findings in that regard on a future date. I intuitively believed that with gravity not putting any pressure on you, that you would need to compensate for that lack of weight. Though, as I looked into it more, the picture seemed more and more unclear:

“Wait, what?” I said. “It’s the OPPOSITE??”

Of course something like this couldn’t be so simple, and frankly how dare I assume something like that when apparently this is something we’ve observed since the 70s. A surface level explanation I’ve heard is water weight, but some of these observations have been made over the course of months, and maybe even years. Astronauts say they eat all they want to eat, and yet they end up somehow losing weight. Only 1 astronaut has ever gained weight in space, with all the others losing it. From what I’ve read it’s the same with mice. This isn’t a subject that has been researched too deeply yet, but with the advent of space flight for the average Joe, it’s something that will probably increasingly be researched in the years to come.

Running theories have gone wild with how this is, but this seems to be some kind of interaction that takes place in microgravity specifically.

So, I am actually quite confused at the moment, and for anyone fluent in the subject I really implore you to enlighten me on this, and why this might be. Is this:

  1. A problem with microgravity specifically, and on somewhere like the moon it would be different, due to there being some gravity, and the food couldn’t “float around in their stomachs”, but still recieve the desired effect of lessening the strain of the weight?
  2. A symptom of the astronauts’ training?
  3. Me misinterpreting these results and it is just muscle mass that’s being affected due to the highly known atrophy of muscles that occurs in space?

Like, what’s going on here?

Are there any solutions to these problems besides what I listed, or are my dreams of Fully Automated Luxury Ace Space Fat Fetishism dashed?


A combination of two and three.
Astronauts need to be pretty much the most physically fit human beings possible to make up for the fact that the act of launching a human being into orbit/space puts immense strain on their bodies, so those who are less than absolutely healthy will pretty much either pass out or die on the way up.
As well as the fact muscle and bone are much denser than fat. Like, much denser than fat, and they lose about 20% of both in less than 14 days in space, which needs to be mitigated by exercise or the astronauts will experience complications, and death. This is mitigated by exercise, which is why astronauts can stay in space for longer periods of time, but guess what, exercise burns fat.

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Thank you for your response! This is one of the first times in a subject like this I’ve been fully stumped, which is weird given how swiftly you replied. I must just not be in the right headspace, then…

Hm, are there any examples of how sci-fi writers, and maybe even modern companies with ambitions of commercial space flight have tried tackling this problem in a realistic way?

Also, just like you elucidated here, it’s not just people who aren’t overweight, but you basically need to be a trained fighter pilot and more to withstand the Gs necessary to leave Earth’s orbit. Other planets might be different, but our’s definitely.

As much as I want in real life for people to stay healthy, it’s an unrealistic standard to hold everyone to at least in the next 200-300 years, especially as being physically inclined becomes less and less important in a society in which robots can do it better.

Is it just the current models of these ships? Or will this always be a problem?

Very true. It was something I knew but did not factor into this. Very insightful.

Once again, have there been any solutions for this that don’t just magic it away with simulated gravity?

I ask this because simulated gravity is mostly clap-trap in the real world, and if we’re talking about near future sci-fi then we need to keep this into account. The most workable example is literally having an interior that spins, and using the force of the spin to simulate Earth-like gravity, but this like anything else would use energy. This energy I wager would better be used actually flying the ship, and in sci-fi settings where ship to ship combat is common, energy that should be used on defenses.

This being said, artificial gravity is something that’s relatively commonplace in sci-fi and not weird to see at all in even more realistic takes, but it’s still a good thought exercise in my opinion, not only for fetish related and adjacent writing, but also for general purpose sci-fi as well.

You must take into account how long certain crews must remain on said ship as well as the purpose of the ship. Take for instance the Nostromo (I think that was its name was) in Alien, a ship of that size doesn’t need artificial gravity however since the crew on board is on there for years (spent on cryostasis sure but they would float were it not for the gravity) it makes sense to have Earth-like gravity to mitigate the complications put on the body. Imagine if there was no gravity, and taking into account what is said above, then we would see Ripley be too weak to even run around and try to fend off the Xenomorph as without gravity her body would not be able to lift itself up.
The same goes for warships, the need for gravity is more important on those vessels compared to space truckers. Take the Venator from Star Wars or the Star Destroyer, why have gravity on those then? Well each vessel holds a significant amount of soldiers that need to be in top shape for potential landing, losing muscle and bone mass would severely hinder such operations. This even goes for starfighter pilots, they also need to be in top shape to keep their wits about them as they go into dogfights. Having gravity also sort of takes away that they are in space; no need to worry about food flying about (or having to slurp out of packets of juice), able to sleep as you would on solid ground, and bring a sense of normalcy to the terrifying possibility of the ship being ruptured and sucking men out into space. So in a way, it is a morale boost.
But then what about the Separatist’s ships, why have gravity on them? Well this most likely brings up the last option of why artificial gravity is needed, too costly to have everything else attached with magnets. Think about if the droids were fitted with magnetic feet then it would through their gait off enough that new expensive designs must be made to compensate for it. Look at the Vulture droids of how big those things are, all so they can attach to the sides of the ships and engage quickly. Yet this leaves them exposed as again, they are big droids.

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This is a treasure trove of good examples, but you’re more talking about applications of artificial gravity.

I’m talking about some sort of solution for this problem that does not involve artificial gravity, because artificial gravity is only possible and affordable with far future level tech.

Basically: In a near future sci-fi story, in which artificial gravity is still improbable, how would a writer get around this problem?

It doesn’t have to be rooted in science fact since I don’t really think many here are space engineers, but more just something creative that adds a more unique twinge to a sci-fi world…

…and theoretically might make moving & completing tasks while a larger size more possible…

See, this is still a weight gain forum. :wink:

I don’t know. I just think it would be neat. I just can’t get passed a lot of these downsides that as you pointed out would be pretty debilitating, and also the main point of this post is how I learned that it’s actually pretty hard.

Another more simply worded question: Can we get fat IN SPACE without dying? And if not, is it any different in any environment where the gravity is just lesser like for example martian gravity?

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The ‘current’ solutions are acceleration and spin. Both well shown in The Expanse.

If you are on a ship going somewhere it makes sense to be either accelerating or decelerating (flip and burn). So you build your ships like a tower block with the drive at the bottom (rather than a like cruise ship with the drive at the rear). You get to choose how much acceleration your drive produces, and thus the strength of the local ‘gravity’. You only experience microgravity when you cut thrust and go on the float.

If you are on a station (asteroid/planetoid) you give it spin and build the floors on the outside. The closer you are to the centre the less ‘gravity’ there is (eg. the Navoo) - so you get lighter as you climb stairs.

Of course, as a writer, you can find any solution you want so long as it is basically self-consistent. “After years of research into the long term effects of space flight on body mass all residents of low-gravity worlds are required to take company issued synthetic ghrelin capsules daily. Some chose to abuse this, and trade services for black-market supplies”.

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Dingo! Big fan! Sorry I didn’t back to you on Patreon that one time. I was just really nervous at the time about all this. I’m also going to try becoming a patron again soon hopefully! Thank you for giving my little thread a visit.

That is quite clever actually. I’ve always just heard of the spinning one. This uses the ship’s own acceleration. That’s very neat.

Maybe I am overthinking it. I wouldn’t be me without that though.


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For what it’s worth too, it’s always good to analyze the bones of your story, and see what it is you’re trying to do, and that everything serves that end goal. In this case, I assume to make compelling kinky fat fics, with AN grounding in real world understandings.

Ask yourself the following questions:

-Do I care about the health and the effects of the body in microgravity? If so, how much, to what degree, and why? There are obvious answers, of course.

It’s fat, it’s inherently personal and deeply about the body, so you’d want to have finer details, or the health aspect is some degree of kinky, yadda yadda. See what you come up with.

-Okay, how does this enhance the fic? What’s the feeling I wanna engender in my readers? Is it even about feelings, or is it just by putting the fic out there, do you want to inspire other people to take the idea and just run with it!

Basically, just focus on the bones of what matters most, and then beeline for it. Drive your story like you stole it, and filled it with drugs.You’ve got places to BE.

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Thank you for the advice! I am already aware of this however.

In writing classes, one of the first things they tell you is to “consider your audience”, and part of that, or a step adjacent is to consider the kind of story you even want to write. If something like realism to this degree is not important for the story at hand, it can sometimes be superfluous, and needs to be removed.

This isn’t for any particular story I was writing, however. This is only an exercize in worldbuilding. Particularly it is an exercize in sci-fi, WG/fat fetishism, and their interactions in a more realistic/nearer future sci-fi environment that I not only thought would benefit me, but maybe someone else as well.