You need about a 1 gram of omega 3 fats every day, and about 2-3 grams of omega 6 fats every day. You also need 1000mg of calcium and 1g of protein per 2lb of body weight (at minimum, more for bodybuilders).
After that, I'd recommend a green salad every day, to make sure you get enough antioxidants and vitamins.
Its definitely not as simple as calories in vs calories out, despite what many believe. If you restricted your calories per day to 2000, but ate them entirely in the form of carbs, it would be difficult to lose weight, especially if you grazed throughout the day.