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In brief: Probably. Celery is mostly fiber and water with little food content. It has been estimated that the calories expended in preparation, eating and digesting celeray are higher than the amount ingested by eating celery. Thus you can loss calories whilst filling yourself as long as you eat plain celery. Nothing untoward can come from eating celery.
I don't mean to step on the obvious here, but if 1kg of celery per day was all you ate (meaning that you allow no other caloric intake) you would certainly lose weight and probably quite rapidly. However, over an extended peiod of time, you would eventually become malnourished and probably die.