Fattening others

I want to fatten my big boy nice and plump. At least double what he weighs now. However, I also want him to lug all that weight around without feeling too uncomfortable.

We live in different countries, so I can't be there to help him. I love exercise myself, but I don't think my routine will work for him. Especially because what calories I don't burn off become pure muscle.

What's the best way to do this?

What worked well for my wife was cycling. It was great cardio but didn't seem to take weight off like running.

She would do spin class and grew a gloriously large ass due to the leg muscle. This was before she became my feedee but also not obsessing over calories.

She hasn't done spin in years and has really fattened up over the pandemic. At her current weight it would be very interesting is he gets back into spin classes...

Power Lifting and light swimming. Mostly keeps the fat but gives you the strength and flexibility to keep waddling in to the high 600s with ease.