Steroids are used medically to prevent muscle wasting, and there have been some papers in older gentlemen (if my memory serves me correctly) using anabolic steroids to improve the body composition, with minimal or no exercise.
The doses used were physiological though, more like HRT, rather than the supra-physiological doses used by most BBers.
I think you need to think about what you mean by 'weight'. Weight could be from fat, water, muscle, bone growth (thickening), or organ growth.
If what you are seeking is muscle growth, training is required.
Muscle is a very metabollically expensive tissue, and our evolutionary history and physiology is not designed to maintain excessive levels of muscle.
Of course there are ways around this.......................