We know that weight of a body is the force with which the body is attracted towards the centre of earth.

W = m × g

Where, m = Mass of the body

And, g = Acceleration due to gravity

The mass of a body or object is constant and does not change from place to place.

But acceleration due to gravity is inversely proportional to the square of the distance from the centre of earth. So, as we go up from surface of the earth, the distance from the centre of earth increases and hence value of g decreases.

Since, W = m × g

So, as the g decreases, weight of the body also decreases with increase in height above the earth. Thus, as we go higher above the surface of the earth the weight of the body decreases.