It occurs to me that you will need to get enough calories in to gain weight, but unfortunately most calorie dense foods are on the acid side (cereal grains – pasta, bread; meats and dairy).

A way to keep an alkaline balance with a higher calorie diet would be to eat an alkaline starch. I was just looking through a PRAL table and noticed that potatoes (all kinds) and sweet potatoes are alkaline, so you can get your calories without eating too many acid foods.

So I think to lose weight whilst being alkaline you can balance your proteins (acid) with greens and fruits (low calories). And to gain weight you can balance your proteins with starches, greens and fruits. A plus is that you can prepare your alkaline starches in anyway to complement your schedule and meal.

Sorry to sound like a potato salesman but it makes sense to me.