Do Celery have negative calories?

No food has negative calories. The lowest amount of calories is zero in the drinking water

An 8" stalk of celery has 6 calories. The fiber-like stuff in the stalk is called cellulose. It takes about 12 calories to break down the cellulose by the digestive system.

6 Calories in the celery - 12 calories to breakdown cellulose = - 6.00 calories net

The celery is some times referred to as having negative calories because of this net negative calorie effect

The net negative calorie effect makes celery an ideal snack to satiate hunger.