“Negative-calorie foods like celery burn more calories than they contain.”
Strong confidence because a direct human calorimetry study found that digesting 100 g of celery used less energy than the celery provided. The proposed “negative-calorie” mechanism is therefore false for the standard example, although the study was small and tested only celery.
Celery is very low in calories, but digesting it does not burn more energy than it provides. “Negative-calorie food” is a catchy label, not a demonstrated property.
In a small study, 100 g of celery provided about 16 kcal and increased energy expenditure by about 13.8 kcal over three hours. That left a small positive energy balance before considering the rest of the diet.
Safety note: Celery is nutritious for most people but can cause serious allergy in susceptible people and contains vitamin K, which should be kept consistent rather than abruptly changed when taking warfarin. Very restrictive “negative-calorie” diets can be nutritionally inadequate.
Talk to a healthcare professional if: Seek urgent care for swelling, breathing trouble or faintness after eating. Ask for help if weight-loss rules are becoming highly restrictive or if you take warfarin and plan a major dietary change.
Low-calorie, water-rich vegetables can add volume and nutrients to meals. Their benefit is low energy density and substitution, not calories disappearing during digestion.
Use vegetables you enjoy to add volume and variety, without relying on “negative-calorie” math.