The astronaut thing sounded interesting, so I looked it up, but it doesn't seem to be the case: https://www.sciencenews.org/blog/food-thought/zero-gravity-diet Astronauts tend to lose weight, but it's because they eat less (for reasons not well understood). Moving around in zero-g burns just as many calories as moving around on the ground, but not vastly more.  If you wanna eat 10,000 calories a day and not get fat, try exploring Antarctica.