Low carb can mean 100 carbs to 10 carbs.

Low carb-- eating little to no grains, but using greens and some root crops like sweet potatos and beets and carrots are high value. Im not saying eat a sweet potato every day, but think a half or a quarter every few days.

QUality meats are important. Macademia nuts are as much fat as protein, and while expensive, make for an occassional snack.

Hopefully you are slowly increasing your exercise and movement. I used sitting ecercises, mostly flexing movements, to get my body moving again, as even that was a challenge. Slow and progressive makes for fewer injuries, too.

You can eat lots of fats and gain weight. Getting fatter is usually easier than building mucsle again. But regular movement, like just moveing the body to get to the kitchen to eat,or to the bathroom can be a trial initially, depending on your starting point. Basic house chores can also difficult.

You dont need a lot of protein to start building the muscles. More work than last week, with a normal portion of protein. A pound of meat a day has a fair amount of protein depending on the cut and animal.

The extra protein will be used as glucose. Which will help with weight gain.

You didnt actually say if y ou are interested in ketosis, because you can eat low carb and gain weight..... and not be in ketosis or the opposite and still be in ketosis ......

Mostly moderate exercise and modest eating will get you where you want to be.....