From my POV, diet and brainpower are linked and I read somewhere that male brains continue maturing even in their 20s. Quality calories = quality energy and you need energy to focus and build your body. The brain is made up of 60 percent fat so I think a "smart" diet might include high quality fat instead of a large amounts of carbs (of course we need some carbs). While tuna has high quality fat it also contains traces of mercury which is not good for our brains. Because of this, tuna should be limited to one can a week--try canned sardines or salmon instead. A quick and simple calculation for the calories we need is to multiply our ideal weight by 10 (females) or 11 (males). So since I think my weight should be 120 then the calories needed to maintain that weight would be 1200 calories a day. For a guy that should weigh 170 pounds, it would be 1870 calories a day. Many jobs in the food industry (the types of jobs college students sometimes have) include a free meal with every shift (I have heard this straight from young people and experienced this in a high school and college jobs). Good luck in your academic pursuits!