moderato. adv. 1. (Music, other) at a moderate tempo. 2. (Music, other) (preceded by a tempo marking) a direction indicating that the tempo specified is to be used with restraint: allegro moderato.
While celery is a very low-calorie food, it likely doesn't provide you with negative calories. Mayo Clinic suggests that while it's theoretically possible for negative-calorie foods to exist, there are no reputable scientific studies that prove certain foods cause negative calorie effects.
There are a few miracle foods however that are purported to be negative in calories. These foods essentially contain more water than they do calories and require more calories to utilize them than they hold. Thus, making these foods essentially calorie free. About 75% of a celery stick is actually water; the other 25% is fiber and other roughage.