What are negative calorie foods?

Calories suddenly become very important when one is trying to lose weight.

from LifeStyle - Latest Lifestyle News, Hot Trends, Celebrity Styles & Events https://timesofindia.indiatimes.com/life-style/health-fitness/diet/what-are-negative-calorie-foods-can-they-help-in-weight-loss/life-style/health-fitness/diet/​What-are-negative-calorie-foods/photostory/65439254.cms
via alochona