Negative-calorie foods
A food lower in calorific content that the energy required to eat it. Eating negative calorie foods, so the theory goes, in itself leads to weight loss.
The most widely cited negative food is celery. It isn't negative-calory food, especially when you load it with cream cheese, which is the only sensible way to eat it. It is pointless, tasteless and gets in the way. Rather like legal celery.