Because everybody's calorie intake is very different, you need to make sure you're not over eating the amount of calories you need to sustain a healthy weight. Tracking calories and the food you eat is a very good way to lose weight because it assures that you're eating healthier. For example, instead of eating a mcdonalds cheeseburger for dinner that has 500 calories, you can eat a meal with steak, asparagus, and mashed potatoes for the same amount of calories. The steak is the healthier option because this meal will help you stay fuller longer causing less cravings and it also has good nutritional value vs the cheeseburger will probably have you hungry in the next hour. The negative side of counting calories is not eating enough calories. Calories give you energy so you have motivation to simply walk up the stairs. If you're eating too few calories, you'll always feel tired and crave more calories causing binge eating. Not only does eating little calories cause that, it will help you lose weight, however, it will have really bad negative effects after you lose weight and you will then just gain all the weight back.