I’m guessing there’s something wrong other than diet.
I like the idea of clean food but there are lots of people with boundless energy who eat food that would never pass muster with the clean food crowd so I’m going to say that’s not the problem.
I drink about a quart of heavy cream weekly plus lots of other dairy and I just spent two months in the middle of the desert humping it daily and I had plenty of energy. I don’t think dairy is the problem.
Naturally lettuce is worthless as a source of nutrition other than fiber. Maybe look there but I’m guessing the problem is somewhere else.
Lettuce is worthless as fiber too.
That was my thought. I have Tabouli, canned spinach, or boiled cabbage instead. If I'm in a situation where there are going to be salad greens, I go for the darker ones.