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Your body is still growing in different ways than someone who is in their 20s, just eat as much as you can of whole foods. Canned foods are fine, and getting 1g/kg of bodyweight it protein provides enough so long as you’re also getting other macros and micros.
Do sports, that’s the best way to get and stay in shape, way better than a gym because the practice is consistent plus trains all your functional fitness and coordination versus just lifting weights which does little for flexibility and range of motion. Plus sports look great on resumes, shows you can commit to things and work hard at them.
To start, I’d say you might not really even need 100g a day. My problem back then when I was your age was the fact that I concentrated all my proteins in one meal. For example, a fresh package of chicken from the market would be cooked and eaten by me in one meal. Now, as a student in the dietetics program, I’d say doing things like having a variety of protein sources in each meal can “prolong” that one package of chicken (as in spreading out the serving of chicken over a few meals). As an example, instead of eating all that serving of chicken in the same meal, you could eat 1/3 of it and use other protein sources like eggs and lentils to reach a certain amount of protein you desire. Over the course of the entire day, it’d be easier for you to reach the amount of protein that you wanted to reach. Also, keep in mind this method benefits you, even if proteins from meats are complete proteins because different foods have different benefits.