Just grow and eat veggies and grains. If you're worried about protein, you're worried about the wrong thing (you should instead be worried about getting vitamins, minerals, and a generally varied diet). Everything that made people worried about protein on vegetarian or vegan diets is based on a study purposefully misinterpreted by the meat-and-dairy industry, where that misinterpretation was parroted for decades and disowned by the original author of the study. Just because you can fulfill the same protein profile as meat using plant proteins doesn't mean you need to. The human body evolved to allow us to eat meat opportunistically, not to require it.

Unless you're on an all-fruit diet, you're getting enough protein if you're getting enough calories (literally no matter your exercise regimen). And if you're not getting enough calories, you're starving and protein is one of the last of your concerns anyway.