Elevators and amusement park rides are the closest to weightless that we have felt. Remember that floating astronaut? Well, there is no gravity in space. Although astronauts do lose a lot of weight, it is because food is floating in their stomach.
Gravity is the force with which Earth pulls a body towards its centre. The closer it is, stronger the pull. This is why we don't fall of the Earth into space. Every object in space has gravity be it the Sun, other stars, moons or the planets.
The amount of gravity a body has depends on its size. So, a smaller planet like Mars has lesser gravity and Jupiter and Saturn has more gravity than Earth. Just like the planets, a person with more mass will weigh more because of more gravity. Weight measures the attraction between two objects. The product of mass of an object and gravity of the object it is on is its weight.
The Moon is one-sixth of Earth's size. This means in the Apollo 11 mission when Neil Armstrong and Buzz Aldrin stepped on the Moon on 20th July, 1969, they felt as light as a child. No wonder they were almost floating while walking on it.
Not everyone can become an astronaut. But in the future, if humans wanted to lose weight and space travel becomes affordable, Mars is the place to be, or maybe the Moon. Mars is almost half the size of the Earth. So a person of 100 kilos on Earth would weigh around 50 kilos on Mars without giving up their eating habits. But yes, after staying there for some time, there will be a new benchmark for "overweight". Have fun till then.
But are there people who never put on weight? Check out another Now You Know to find out.