When two objects are near each other, increasing one object’s mass would cause the gravitational force of the object to increase.
The formula for gravitational force (<em>F</em>) is

where <em>m</em> and <em>M</em> are the masses of the two objects, <em>d</em> is the distance between their centres, and <em>G</em> is the gravitational constant.
If we hold <em>M</em> and <em>d</em> constant, we can write
, where 
Thus, gravitational force is <em>directly proportional</em> to the mass of the object.
If you increase the mass of an object, you increase its gravitational force.