Going to college and attending those classes may take all the energy and leave nothing for exercising. Despite this you can do somethings to stay fit while attending you college. You can add the inexpensive exercises like taking the stairs instead of lift, walking around during study breaks, walking or cycling to class etc.
Exercising is not just for staying fit but can also be done for good grades. Studies have shown than students with 3.5+ GPA were 3 times more likely to participate in vigorous activity than students with less than 3.0 GPA.
Not just exercising but also eating the right foods helps in one getting a fit body. Give both your mind and body the right food to function properly.