Psychologically, some diet gurus feel that the desire for sweet-tasting food and drink can be overcome by abstinence of such. Using naturally sweet foods such as fruits tends to help overcome the desire for manufactured sweets, after a time. By using artificially sweetened soft drinks, you are perpetuating your desire for manufactured sweets such as processed bakery foods, according to some dietitians. Carbonated drinks can be bloating. Bloat adds to the desire to overeat.
Carbonation also can upset the digestive tract as well as deplete calcium from the bones.
Diet drinks are also empty calories. They have no nutrients. Dietitians would rather you drink fruit juices that are nutrient dense and add to your overall nutritional health. Regardless of the above, if diet drinks help you achieve your goal in losing weight, we feel they are not harmful, in a broad sense. In balance, it's far better to drink a diet drink than eat a cupcake or drink a non-diet carbonated drink that normally contains 16 teaspoons of sugar.