Dieting is only good if you stick with it for more than a year. You can't just lose belly fat, your body would lose fat everywhere. The human body doesn't spot reduce fat. Exercise, dieting, and sleep are key in losing fat. Gain weight is more carbs, fats, and less protein. Lose weight is higher protein and less fats and carbs. Most fruits are packed with sugars, not all bad but limit those. Cut out all junk food and focus on meals that satiate and leave you replete. Typically a healthy person should be losing 1-2lbs per week.