I would recommend eating healthily and running 3-4 days per week. It makes you feel great, mentally acute, and you know that you're only going to become healthy and live longer, with no side effects.
One way you can eat the same amount of calories and either lose weight or gain no weight is by reducing complex carbs in your diet. Avoid things that are high on glycemic index and you won't feel slow: this doesn't meant cut out all carbs! Eat whole wheat bread, brown rice, dark chocolate if you have carb cravings just lessen the white wheat, high fructose corn syrup, white rice etc...
Combined with regular excercise (at least 3 times a week, at least 45 minutes each time -- with at least 30 minutes of that being cardio) you will feel a lot better and be (or remain) in better shape (if you are worried about losing too much weight or muscle mass simply eat more - but more calories, not more carbs).
Try to move to seasonal fruits, and add raw seasonal vegetables on top of it. Cut out the meat.
(This is probably what I'll be doing when my bf goes out of the country for a month... or at least, that's what I'm telling myself. :)