In a weightless environment, you would not appear thinner in a mirror because the concept of "thinness" is based on the amount of mass an object has relative to its volume, which is not affected by the absence of gravity. Your body would still have the same mass and volume as it does on Earth, so it would appear the same size in a mirror regardless of the presence or absence of gravity.
However, if you were in a weightless environment, you might appear to be floating or drifting in the mirror, which could give the impression that you are thinner than you actually are. This is because in a weightless environment, there is no gravitational force pulling you down, so you would appear to be suspended in midair. This would be an optical illusion, however, as your body's mass and volume would not have changed.
In a weightless environment, you would not appear thinner in a mirror because the concept of "thinness" is based on the amount of mass an object has relative to its volume, which is not affected by the absence of gravity. Your body would still have the same mass and volume as it does on Earth, so it would appear the same size in a mirror regardless of the presence or absence of gravity.
However, if you were in a weightless environment, you might appear to be floating or drifting in the mirror, which could give the impression that you are thinner than you actually are. This is because in a weightless environment, there is no gravitational force pulling you down, so you would appear to be suspended in midair. This would be an optical illusion, however, as your body's mass and volume would not have changed.