Your body mass is the result of your genetics, age, food and exercise. With effort and time you can change it. But at any instant your mass is what it is. Your weight, however, is not. It depends on where you measure it. The acceleration due to gravity at the earths surface is about 9.8 m/s^2. On the moon the acceleration due to gravity is approximately 1.6m/s^2. If you weigh 668 Newtons at CNU (that is about 150 pounds for your Anglophiles), what will you weigh at Tranquility Base on the Moon?