Research has shown that all plants contain protein and at least 14% of the total calories of every plant are protein. Broccoli contains more protein per calorie than steak and, per calorie, spinach is about equal to chicken and fish. Of course, you’ll need to eat a lot more broccoli and spinach to get the same amount of calories that you do from the meat.
I’m a cheating vegan or a picky pescetarian depending on the day of the week. I don’t eat meat other than seafood and I’m very selective about what seafood I do eat — mostly tuna and oysters. I don’t consume dairy other than the occasional ice cream and cake (and cake).1 Even so, 2½ lbs of spinach sounds daunting. Luckily there are other options:
Beans (27% protein), lentils (36%), chickpeas (33%), peas (30%), and kale (22%) provide the greatest opportunity to acquire micronutrients packaged with protein. Practical solutions to add more of these include adding beans/legumes to salads, stews and soups.