Answer: Negative calorie foods are a myth. It is a common misconception that foods high in fiber such as the ones mentioned above burn more calories during digestion than they contain. It’s true that your body doesn’t absorb fiber, but it does absorb the calories associated within the fibrous food. For example, the act of chewing gum burns 11 calories per hour (.183 calories/min). Applying this to a 2 oz serving of celery that contains 8 calories, it would take 43 minutes of chewing to burn 8 calories! No one has that kind of time or could live with a diet that contains a high percentage of total calories coming from these types of foods. The bottom line is you could not include enough of these foods nor chew each one as mentioned in order to make any significant contribution to weight/fat loss.
Fiber-rich foods that are low in calories may aid in weight loss by providing greater volume than, for example, an energy-dense, low volume cheeseburger. Added fiber in the diet may lower your risk of digestive disorders, improve blood cholesterol and reduce diabetes risk. Women under the age of 50 should strive for 25 grams per day while men 50 years and younger should consume 38 grams/day. If you are over the age of 50, the recommendation is 30 and 21 grams for males and females respectively.