Your diet should be designed to fit you, not just a general recommended health diet. Your diet should be adjusted to fit your lifestyle and your goals. If you have a hectic lifestyle then foods will need to be prepared at earlier times and proper preparation needs to be taken to follow your diet guidelines, whereas you may also have the leisure to cook during the week. Your diet should be shaped to fit your goals whether it be weight gains or weight loss with proper recommendations of nutrient ratios and amounts. In general you will want to either increase or restrict your caloric intake by 500kcal/day to net a gain or loss of one pound per week.
By using the proper calorie calculation tool you can find your daily calorie requirements. Then using both the food pyramid as a backing, and also varying food exchanges, construct a diet that fits your needs and nutrient ratio requirements. The new USDA food pyramid is helpful in giving the appropriate ratios of each food group, but it fails to address different body types, training, and goals. The diets designed by this site are designed to meet your goals, but one should remember that the main goal for everyone is to find a healthy eating lifestyle, or a lifetime healthy diet.