"Zero calorie" foods don't exist — everything with any mass has some caloric content. But foods with very low calorie density functionally approximate the idea: they fill you up for essentially no caloric cost, which supports a deficit. Twenty of them below.

Vegetables (12)

1. Cucumber — 16 kcal/100 g
2. Celery — 16 kcal/100 g
3. Lettuce (all varieties) — 15 kcal/100 g
4. Zucchini — 17 kcal/100 g
5. Radishes — 16 kcal/100 g
6. Tomatoes — 18 kcal/100 g
7. Bell peppers — 20 kcal/100 g
8. Cauliflower — 25 kcal/100 g
9. Asparagus — 20 kcal/100 g
10. Spinach — 23 kcal/100 g
11. Cabbage — 25 kcal/100 g
12. Broccoli — 34 kcal/100 g

Fruits (4)

13. Watermelon — 30 kcal/100 g
14. Strawberries — 32 kcal/100 g
15. Cantaloupe — 34 kcal/100 g
16. Grapefruit — 42 kcal/100 g

Proteins (4)

17. Egg whites — 52 kcal/100 g
18. Shrimp — 85 kcal/100 g
19. White fish (cod, tilapia) — 80-100 kcal/100 g
20. Plain non-fat Greek yogurt — 60 kcal/100 g

How to use the list

Fill half your plate with the vegetables. Add a lean protein. Between meals, snack on the fruits. Even eating these to full satiety produces a natural daily calorie deficit for most people. That's the mechanism — not fat burning, just displacement of calorie-dense alternatives with minimal-calorie volume.