Celery sticks, ice water, sugar-free gum—every few months, the promise of a “negative-calorie” hack ricochets through diet culture. The idea is seductive: eat something that costs more energy to digest than it gives you, and let biology do the rest. But does any food actually put you into an energy deficit just by eating it?
Short answer: not in the way the marketing hype suggests. Long answer: understanding why reveals a lot about how your body really spends energy—and how to leverage that knowledge without falling for gimmicks.
What a calorie means—and why it can’t be negative
A calorie on a nutrition label (technically a kilocalorie) is a unit of potential energy contained in food. Regulators use the Atwater system to estimate that energy—roughly 4 kcal per gram of protein, 4 for carbohydrates, and 9 for fat—with adjustments for things like fiber and sugar alcohols. By definition, that chemical energy number can’t be negative. It’s either some energy or none.
That’s different from the energy your body expends to eat, digest, absorb, and process food, known as the thermic effect of food. Across a typical mixed diet, this “processing tax” averages about 10% of the calories you consume. Protein is costliest to handle (roughly 20–30% of its calories are burned during processing), carbs are moderate (5–10%), and fat is cheap to store (0–3%).
This is the kernel of the negative-calorie myth: if digestion burns energy, couldn’t certain foods tip the ledger below zero? In practice, the math never pencils out that way for anything you’d reasonably call food.
Testing the usual suspects: celery, ice water, and gum
Celery and ultra-low-energy produce
Celery, cucumber, lettuce, and other watery vegetables are famously low in calories and high in fiber. A medium celery stalk has roughly 6–10 kcal, most of it from carbohydrate that is only partly digestible. Chewing and digesting it does burn some energy, but you still net positive—even if only slightly.
The upshot: these foods don’t pull you into negative territory, but they are excellent for satiety. They deliver bulk, fluid, and micronutrients for very few calories, which helps with portion control and overall energy balance.
Ice-cold water (and ice)
Water contains no calories, and warming it to body temperature costs a bit of energy. Heating 500 milliliters of near-freezing water by roughly 37°C uses about 18–19 kcal. If you actually eat ice, melting it adds another energy cost, but most people drink cold water, not slush.
Even then, the impact is small. You would need a lot of very cold water to make a meaningful dent in daily energy expenditure, and your body compensates fluid and temperature fluctuations in other ways. Hydration helps appetite management and performance, but it isn’t a weight-loss shortcut.
Chewing gum
Chewing modestly increases energy expenditure—think a trickle, not a torrent. Sugar-free gum often lists zero or a handful of calories per piece, and a brief chew will burn a few calories in the act. Net effect: negligible for weight, though some people find gum helpful to curb snacking, freshen breath, and stimulate saliva.
Konjac noodles, fiber, and the satiety advantage
Konjac (shirataki) noodles and certain gelatinous jellies are mostly water and soluble fiber, registering 10–20 kcal per 100 grams. Fiber is not fully digestible, so fewer of its calories are absorbed, and it slows gastric emptying—both of which can help you feel full on fewer calories.
That doesn’t make them negative-calorie foods, but it does make them useful. Building meals around high-fiber vegetables, legumes, intact whole grains, and water-rich foods is a proven way to reduce calorie density without sacrificing volume. Add lean protein—which has the highest thermic cost—and you get a one-two punch of satiety and a slightly higher processing burn.
Why we don’t engineer “negative-calorie” foods
Occasionally, proposals surface to design foods that are energetically expensive to process or impossible to metabolize. Ideas range from creating mirror-image “D-protein” structures the human gut can’t use to inventing compounds that bind glucose or ATP so the body can’t access them. On paper, that might sound like forced energy loss. In practice, it flirts with real danger.
For starters, the digestive tract is built to break proteins into amino acids before absorption; feed it exotic proteins or polymers and you risk immune reactions, microbiome disruption, or worse. Molecules that sequester energy carriers could cause hypoglycemia or interfere with fundamental cellular processes. History is littered with cautionary tales—think of early weight-loss drugs that blocked nutrient absorption but caused serious gastrointestinal and metabolic side effects.
The safest, evidence-based ways to create a meaningful “processing cost” are already on your plate: prioritize protein, fiber, and minimally processed foods, and let the thermic effect work for you within normal physiology.
The real math of metabolism
Your daily energy burn has three main parts: resting metabolic rate (the baseline to keep you alive), physical activity, and the thermic effect of food. Resting metabolism is the largest portion for most people. Activity is the most flexible lever. Thermic effect is the smallest slice—helpful, but not a magic bullet.
Can you nudge that “processing tax” upward? Yes. Emphasize protein at each meal, choose intact complex carbohydrates and fibrous vegetables over refined options, and chew thoroughly. Small tweaks compound over weeks and months. But the negative-calorie promise—the idea that a food alone can erase its own energy content and then some—doesn’t survive contact with physiology.
How to use the myth to your advantage
- Front-load protein and fiber. Aim for at least 20–30 grams of protein per main meal and include vegetables or legumes for bulk and micronutrients.
- Lower calorie density, not pleasure. Build half your plate with water-rich, high-volume foods—vegetables, fruit, broth-based soups—then add satisfying fats and starches thoughtfully.
- Hydrate strategically. A glass of water before and during meals can help with appetite awareness and pace, even if it isn’t a caloric furnace.
- Eat slowly and chew more. Beyond mindfulness, thorough chewing slightly increases diet-induced thermogenesis and gives your gut-brain axis time to register fullness.
- Be label-savvy. “Zero calories” can reflect rounding rules that permit up to a few calories per serving; small amounts add up across many servings.