Weight Lifting

Strength training or weight lifting is the lifting of heavy weights and / or resistance in a prescribed manner as an exercise or in athletic competition.

The weights and/or resistance does not have to necessarily be a weight plate or a dumbbell, though it should be properly designed.

When you lift weights your body builds muscle. The more muscle you have, the more calories you burn (even at rest). The more calories you burn the less you weigh.

Muscle does not weigh more than fat, it weighs the same but for the same weight it is more compact than fat and it takes up less space.

So a person who exercises regularly will have more muscle than your friend does which means you will take up less space. So clothes which will fit a person who is fat, will appear to be loose on a person who exercises regularly, though their weight appears to be the same.