Eat a romaine salad with some yummy balsamic vinegar (it can be fruit balsamic too if you have a sweet tooth) for only 30 calories and you can add it to any small protein meal. You can eat TWO CUPS of lettuce for 15 calories. You get full quicker without packing on pounds... making that itty-bitty sandwich or piece of meat a LOT more filling.
Others are fresh spinach, celery, pickles and cucumbers, cabbage, and carrots, broccoli, cauliflower, sweet potato, and melons.
. These are great to substitute at restaurants too! Usually if you eat half of the entree (restaurant portions are usually double of triple) and eat a salad or fruit bowl instead of a normal side... you can have what you want without blowing your diet!
Just try not to add bad things ON them!