Gravity would get doubled but the mass would not be doubled
So increase in weight would also be double of the previous weight
W=mg
Now, W'=m*2g
W'=2*mg, and mg is equal to W
W'=2*W
Hence proved
Eg Weight is 60N and gravity is,for instance 10m/s^2
Therefore mass is 6kg
Now g=20m/s^2
Therefor increased weight =6*20=120N