[jokethrowaway]

This could be a B12 deficiency.

B12 deficiency stores can deplete over 2-4 years so it will be a while before you notice. You also need very small amounts (monkeys get their B12 intake by accidentally eating bugs on their bananas).

I tried going vegetarian for a period of my life and I started feeling extremely tired after a while. I stopped doing it mainly because getting protein is hard and I didn't notice any other positive changes.

[roebk]

I'm usually surprised when people say they struggled with protein intake. Protein is widely available and eating seeds, pulses, nuts, oats, grains and a load of veggies should get most people to that required ~50g of daily protein intake.