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No food has zero calories, and nothing you eat burns more energy than it contains. What does exist is a group of foods so low in energy for their bulk that a large portion costs you less than a single tablespoon of oil — and that difference is genuinely useful if you are trying to eat less without feeling like you are eating less.
Below are fifteen of them with their actual calorie counts per 100 grams, what the research says about why low-energy-density foods help, and the one habit that quietly cancels the whole effect. Figures are for raw portions and come from standard food composition data; cooking method changes them, sometimes dramatically.
What “almost zero calories” actually means
The useful concept is energy density: calories per gram of food. Vegetables and fruit sit at the bottom of that scale because they are mostly water and fibre, neither of which contributes meaningful energy. A medium raw carrot is about 88 percent water and roughly 25 calories. Half a grapefruit is about 90 percent water and around 64 calories.
Eating more low-energy-density food is one of the better-supported behavioural strategies in weight management. The mechanism is not metabolic trickery — it is volume. You eat a satisfying amount of food, the stomach registers the bulk, and the calorie total lands lower than it would have. The same principle explains why a cup of grapes is about 104 calories while a cup of raisins — the same fruit with the water removed — is closer to 480.
The “negative calorie” claim is not true
Digesting food does cost energy. That cost, the thermic effect of food, is a fraction of what the food provides, never more than it. Celery is the food usually named as the exception. One small study measured it directly and found celery delivers about 16 calories per 100 grams, of which only a small fraction is ultimately absorbed. That is very low. It is not negative, and no food is.
This matters practically: treating these foods as free does not make them free, and building a diet on the belief that some foods cancel others out tends to end badly.
The 15 foods, by calories per 100 grams
| Food (raw) | Calories per 100 g | Worth knowing |
|---|---|---|
| Watercress | ~11 | Peppery; wilts into soups and eggs without adding bulk fat |
| Iceberg lettuce | ~14 | Mostly water; crunch without much fibre or micronutrient value |
| Cucumber | ~15 | About 96% water — the highest on this list |
| Celery | ~16 | The one usually mislabelled “negative calorie” |
| Radishes | ~16 | Holds texture when raw; good in place of crackers for dips |
| Zucchini | ~17 | Absorbs oil readily when fried — cook it dry or roast it |
| Tomatoes | ~18 | Cooked tomatoes make lycopene more available |
| Asparagus | ~20 | Filling relative to its calorie cost |
| Green bell pepper | ~20 | Red and yellow are slightly higher, around 26-31 |
| White mushrooms | ~22 | Meaty texture; a common partial swap for mince in sauces |
| Spinach | ~23 | Cooks down to roughly a tenth of its raw volume |
| Cabbage | ~25 | Cheap, keeps for weeks, works raw or cooked |
| Cauliflower | ~25 | The usual rice and mash substitute, at a fraction of the calories |
| Strawberries | ~32 | The lowest-calorie common fruit by weight |
| Broccoli | ~34 | Highest here, and the most protein and fibre per gram |
For scale: all fifteen foods at 100 grams each would total roughly 300 calories — about the same as a large bagel, and considerably more food than most people can finish in one sitting.
What these foods change, and what they don’t
They lower the energy density of a meal. Adding 150 grams of vegetables to a plate and removing an equivalent volume of something denser is a real reduction, repeated daily, without portion-size discipline doing the work.
They do not burn fat, raise metabolic rate in any meaningful way, or offset other food. A plate of vegetables eaten alongside an unchanged meal adds calories rather than subtracting them. The benefit comes from displacement, not addition.
The habit that cancels it
Preparation is where the arithmetic breaks. One tablespoon of olive oil is roughly 120 calories — more than every vegetable on this list at 100 grams each, several times over. Two tablespoons of a creamy dressing can outweigh the salad underneath it by a factor of five or more. Roasting vegetables in oil, sautéing them in butter, or finishing them with cheese are all reasonable things to do; they simply mean the dish is no longer a low-calorie dish, and it is worth being honest with yourself about which one you are eating.
Practical ways to use them
- Displace rather than add. Half the rice, double the cauliflower. Half the pasta, add courgette. The meal stays the same size.
- Front-load the meal. Vegetables or a broth-based soup first tends to reduce how much of the denser course gets eaten.
- Prep for laziness. Washed, cut vegetables in a visible container get eaten. A whole cabbage in a drawer does not.
- Season instead of coating. Lemon, vinegar, herbs, chilli, mustard and garlic add flavour at almost no calorie cost; oil and cream add flavour at a considerable one.
- Cook them dry. Roast on parchment, air-fry, steam, or dry-sear in a non-stick pan, then add a measured amount of fat at the end where you can taste it.
Who should take care
Very high intakes of cruciferous vegetables — broccoli, cauliflower, cabbage — cause bloating and discomfort in some people, particularly anyone managing IBS. Leafy greens are high in vitamin K, which interacts with warfarin and similar anticoagulants; consistency matters more than avoidance, and that is a conversation to have with whoever manages your prescription. If you have kidney disease, potassium intake from vegetables may need managing. None of this makes these foods unsuitable; it means individual circumstances override general advice.
Frequently Asked Questions
Is celery really a negative-calorie food?
No. It is about 16 calories per 100 grams and a small study found only a fraction of that is absorbed, which makes it very low — but digestion never costs more energy than the food supplies. No food has a negative net calorie balance.
Can I eat unlimited amounts of these?
Practically, most people reach their limit on volume long before the calories matter. But “unlimited” is the wrong frame: 500 grams of broccoli is still around 170 calories, and a diet built only on these foods would fall short on protein and fat, both of which you need.
Are frozen vegetables as good as fresh?
For this purpose, yes. Frozen vegetables are picked and frozen quickly and their nutrient content holds up well — often better than fresh produce that has spent a week in transit. They are also cheaper and do not spoil, which matters more for whether you actually eat them.
Does juicing or blending them work the same way?
Blending keeps the fibre; juicing removes most of it along with much of the bulk. Since the effect here depends on volume and fibre, whole or blended beats juiced. Juice also tends to be consumed faster than the same food eaten.
Should I eat them before or with a meal?
Before, if you are aiming to eat less of what follows — trials on soup and salad starters point that way. Alongside is fine too, and the more reliable question is whether they are on the plate at all rather than the order in which they arrive.
Sources & References
- Mayo Clinic — Weight loss: Feel full on fewer calories
- Examine.com — Can food have negative calories?
- Rolls BJ — Dietary energy density: applying behavioural science to weight management, Nutrition Bulletin, 2017
- National Institutes of Health — Increasing low-energy-dense foods and decreasing high-energy-dense foods differently influence weight loss trial outcomes