If the mass of the earth increase, with no change in radius, one's weight would also increase considerably.
The reason for this is that, the gravitational force of attraction between the two bodies will increase.
The gravitational force of attraction between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
So, increasing the mass of the earth will increase the gravitational force on one's body and hence, an increase in weight.
