The problem here is that grains are the most common source of carbohydrates, and carbohydrates are very important to gaining weight. Yes, protein is important to build muscle, but the importance can be overstated. You need protein, but you need that protein to be in excess of how many calories you need in energy. In other words, if you are not eating enough calories, the protein is probably going to be burned up for energy instead of adding to your body weight.
And if you want lots and lots of calories, you need carbohydrates. Let me demonstrate.
Check out this pile of non-kosher-for-Passover rice.
Beans and chickpeas, which some Jews eat during Passover, are not quite as efficient. They are not as calorie dense, and have more protein and water. To get the same number of calories you would have to eat this many.
So that brings us back to grains. The only grains I can eat during Passover are matzo. But matzo are big and dry and airy. It's hard to eat a lot in one go. This whole box only has 1,700 calories:
The good news is that by sundown tonight, Passover will be over and I can get back to the pasta, brown rice and oatmeal that makes my graph tilt pleasingly upwards.
Next week I'll write about strategy, and now to mix a simple 1,300 calorie beverage.