I agree fully, I weighed 230 at my peak in a warehouse and unfortunately it was not good weight. You do a little of this and that, but you dont do consitent movements to "failure" like you do in a gym, its NOT the same thing.
I honestly dont predict good weight gain, from my own experience. I had a hard time going to the gym somedays, once I had to unload a 48 foot truck NOT palletized, by myself. This means when the rollers get jammed I freed the jam. I had to push everything out box by box, I wish I could remember the peice count.
Then after things were on the rollers, I had to scan them one by one by moving to the front of the truck. Basically I moved as fast as I possibly could (this means running) for 8 hours straight with only breaks long enough to down some of the 2 liter soda I brought in, it was gone within about 90 minutes. I had severe chafing on the insides of my legs from that day, those are the days that you feel you aged 10 years and dont feel like going to the gym at all. After scanning stuff I had to load them on "U-Boats" and then roll them down the isles. The entire 48 feet were unloaded by me by the end of my shift. This could be anything from TVs to toaster ovens.
Anyhow, from my own experience if you dont go to a gym then dont look to gain more than maybe 10 pounds, it does not substitute lifting.