Once vegetables get down into the teens of calories per 100 g, the ranking differences become tiny. Most of these foods are very low in energy because they are mostly water.
Some of the lowest per 100 g
| Raw vegetable | Approx. kcal/100 g |
|---|---|
| Cucumber with peel | ~15 |
| Lettuce | ~15–17 |
| Zucchini | ~17 |
| Tomato | ~18 |
| Green bell pepper | ~20 |
| Spinach | ~23 |
Values are rounded from composition databases such as USDA FoodData Central.
Cooking can change calorie density
Boiling without added fat contributes essentially no new calories, although water gain or loss can change calories per 100 g. Roasting removes water and concentrates the food. Two tablespoons of oil add roughly 240 calories to the dish regardless of whether the vegetable started at 15 or 25 calories per 100 g.
Lower calorie does not automatically mean better
Broccoli, carrots, or peas may contain more calories than cucumber, but they also provide different amounts of fiber, carotenoids, vitamin C, folate, or protein. Energy density is only one dimension.
Low calories per 100 g usually means a lot of water
Lettuce, cucumber, zucchini and other very low-energy vegetables contain a great deal of water. That lets you eat a large volume for relatively few calories, but it does not make them automatically “better” than slightly higher-calorie vegetables. Peas, corn or carrots can provide more energy while also contributing more carbohydrate, fiber or micronutrients per serving.
Serving size matters more than tiny ranking gaps
Two hundred grams of zucchini is around 34 calories and 200 g of tomato around 36. That 2-calorie difference is meaningless in practice. The value of this list is understanding which foods are very low in energy, not chasing first place.
For vegetables, cooking method and added ingredients usually change the final plate more than a few calories between raw varieties.
Use low-calorie vegetables to build volume, not to chase tiny numeric gaps
Cucumber, lettuce, zucchini, tomato, peppers, and spinach all sit in a very low calorie range because water makes up most of their weight. The difference between 15 and 23 calories per 100 grams is nutritionally small in a normal meal. A more useful question is how much you enjoy the vegetable, how much fiber and micronutrients it contributes, and whether the preparation helps you eat a satisfying amount.
Cooking can concentrate calories per 100 grams simply by removing water, even when no fat is added. Roasted zucchini may therefore look more calorie-dense than raw zucchini by weight because the cooked portion contains less water. Adding oil, cheese, creamy dressing, nuts, or seeds can change the energy content much more than choosing tomato instead of bell pepper.
Low energy density can be useful when you want a larger plate for relatively few calories, but vegetables are not complete meals by themselves. Pair them with a protein source and, when appropriate, whole grains, potatoes, legumes, or healthy fats. That combination is usually more filling and nutritionally balanced than an enormous bowl of raw vegetables with very little else.
The ranking is best treated as a menu of options rather than a competition. Choose watery vegetables for crunch and volume, leafy greens for folate and vitamin K, peppers for vitamin C, and mixed vegetables for variety. The calorie difference among these foods is rarely the factor that makes or breaks a diet.
Portioning by volume rather than weight also changes perception. A large bowl of leafy greens may weigh less than one medium tomato, so calorie comparisons per 100 grams do not tell you how full the plate will look. This is another reason energy density is more useful as a broad concept than as a precise ranking between individual vegetables.
Frozen and canned vegetables can fit the same goal. Plain frozen vegetables often have a calorie profile close to their fresh counterparts, while canned products may contain added sodium and prepared vegetables may include sauces or butter. Read the ingredient list instead of assuming “fresh” is automatically lowest calorie. What is added during preparation usually matters more than the preservation method itself.
Seasonality can help more than memorizing the bottom of the calorie list. Vegetables that are fresh, affordable, and enjoyable are easier to eat consistently. A person who loves roasted peppers may get more practical benefit from eating them regularly than from forcing down plain lettuce because it ranks a few calories lower. Adherence and variety beat microscopic ranking differences.
Sources
- USDA FoodData Central — Composition database used for approximate energy values of raw vegetables.