There are various ways to lose weight, and this can be achieved without having to do exercise, although this might be attained at a delayed speed.
Diet is integral to managing and regulating weight concerns, so it is possible that you have noticed a friend or stranger losing weight by simply eating right.
Not only this, but sometimes exercise can work it's own way into our lives when we are busy rushing around and thus end up burning the calories regardless.
If one is not heavily invested in an exercise regimen, it is likely that there could be pockets of fat left over in various parts of the body. Exercise can definitely correct this, especially toning and firming exercises like weight training, and quick bursts of cardio training to target fat calls.
I hope this helps.