Did You Know: There’s no such thing as zero-calorie foods — Here’s the truth behind low-calorie veggies and products!

Did You Know: The idea of “zero-calorie” or negative-calorie foods has long thrilled dieters and wellness enthusiasts alike. From crunchy celery sticks to crisp cucumbers and peppery watercress, many believe that some foods could require more energy to digest than they actually contain, effectively burning calories while you eat them. But science suggests otherwise: no natural food has truly zero calories, and there’s no credible evidence that any food causes a net loss of energy by eating it.

Did You Know: What Science Says About “Zero-Calorie Foods”

In popular diet talks and social media posts, celery, lettuce, watercress and similar foods are often touted as zero- or negative-calorie because they are extremely low in calories and high in water content. The thinking goes that the human body uses more energy to chew, digest and absorb these foods than the calories they provide.

However, nutrition experts and scientific studies have debunked this idea. According to research on so-called negative-calorie foods, every food contains calories, and even the lowest-calorie fruits and vegetables contain more energy than the body expends to process them.


For instance, celery, perhaps the poster child of zero-calorie foods, contains measurable calories (about 14 per 100 grams) and the energy needed to digest it does not exceed this amount. The body’s energy expenditure during digestion, known as the thermic effect of food (TEF), generally uses a small fraction of the calories consumed, roughly 5–10% for carbohydrates and higher for proteins, but not enough to make the food net-calorie negative.

Did You Know: Why No Food Is Truly Zero Calorie

From a biological perspective, calories are a measure of energy stored in food, specifically the energy released when molecules such as carbohydrates, fats and proteins are broken down in the body. Because nearly all foods contain at least some of these energy-yielding nutrients, they always contribute calories, even if very few.

Only a handful of consumables such as plain water, black coffee and some artificial sweeteners effectively contain no usable calories. Water provides no energy because it lacks usable nutrients; similarly, certain artificial sweeteners are not metabolised into energy by the human body.

Even foods with minimal calories are unlikely to require more energy to digest than the energy they deliver. A 2019 study using bearded dragons, which have a digestive system similar in basic mechanisms to humans, found that even celery provided a net positive energy gain after accounting for digestion and excretion.

Did You Know: The Thermic Effect of Food Explained

The thermic effect of food (TEF) refers to the energy your body uses to digest, absorb and metabolise nutrients. While this does burn calories, the amount is a portion of the calories provided by the food, not more than them. TEF varies by nutrient type, proteins require more energy to process than carbohydrates or fats, but it always remains a fraction of the total energy consumed.

Because the TEF is relatively small, even extremely low-calorie foods like watercress still provide net energy. To qualify as truly zero-calorie in biological terms, a food would need to require as much or more energy to digest as it supplies, something that, according to current science, doesn’t happen in natural diets.

Did You Know: What This Means for Weight Management

Although “zero-calorie foods” as a concept are scientifically inaccurate, this doesn’t mean low-calorie foods aren’t valuable for nutrition or weight control. Foods high in water and fiber, such as celery, cucumbers, lettuce and watercress, provide bulk and satiety with relatively few calories. This makes them excellent components of a balanced, calorie-controlled diet.

In other words, these foods can still help create a calorie deficit, essential for weight loss, by replacing higher-calorie options and keeping overall calorie intake lower. But the mechanism isn’t magic: it’s simply good dietary practice.

Did You Know: Myth Versus Reality

The bottom line is clear: there is no evidence to support the existence of true zero-calorie foods in the natural world. Every food that contains usable nutrients provides energy, and the energy the body spends processing it does not outweigh the energy it supplies. The allure of zero-calorie or negative-calorie foods may be strong, but the science does not back it up.

That said, choosing low-calorie, nutrient-rich foods as part of a wholesome diet remains a smart strategy for health and weight management, just don’t expect them to burn more calories than you eat!