The false belief that some foods ‘burn’ more calories than they provide can lead you to gain weight when incorporating them into your diet.

Cold water with lime.

When it comes to losing weight as a New Year’s resolution, any means seems to be a good one: from impossible diets with wacky names, to detox shakes or fallacies based on magical thinking but without scientific evidence.

One of the “tricks” that has become popular in Spain are known as negative calories. In theory, there would be foods that burn more energy to consume and digest than the calories they provide. By eating them, therefore, we would lose weight.

Unfortunately This is neither true nor has it ever been proven, as recently clarified by 3 experts in nutrition and human physiology on the platform Metafact.io.

The truth about negative calories

As Louise Dunford, an expert in nutrition and physiology at the University of Montford in the United Kingdom, points out, some need to be clarified basic concepts: a calorie, or rather kilocalorie, is the unit of energy in food.

Packaged foods usually express their level of kilocalories (kcal) for every 100 grams of product on their labeling. We consume calories when we eat food, and by processing and digesting it, we also expend energy.

In short, it will take energy to perform three basic activities in life:

– Energy for keep us alive at rest, that is, for the basic processes of life.

– Energy for digest food, or what is known as the thermal effect of the food. There is an increase in the metabolic rate or energy expenditure each time we eat, since energy is required to digest food and absorb its nutrients.

– Energy for engage in physical activity and exercise, beyond the basic processes at rest.

It should be noted that the metabolism is divided into more activities where caloric expenditure is required, as we already explained in its day in EL ESPAÑOL, but this is a good summary in this regard.

The theory behind negative calorie foods It would imply that these foods would have a lower energy or caloric content than the amount of energy needed to digest and absorb them.

As Dunford explains, in theory it could be plausible; however, even food very low in calories like celery they contain more calories than is necessary to break them down and absorb them.

Some of the so-called “negative calorie” foods It would be precisely celery, tomatoes, cucumber, broccoli, lettuce or carrots. They are all low in calories and nutrient dense, but have no “negative calories.” Currently there is no scientific evidence in this regard, and it has been studied a lot.

Another of the experts consulted, Tim Crowe, expert in nutrition of the environment Thinking Nutrition, talks about celery again: contains 95% water, but still has about 15 kcal per 100 grams of food.

Although it is true, he explains, that the thermic effect of food has been studied and is real, this only represents approximately 10% of the energy of the food consumed. Therefore, even celery would imply a consumption of additional calories after its digestion. It would be very little energy, but it would not be a negative effect in any case.

It has even been mentioned that cold water could have negative calories, as Cornelie Nienaber-Rousseau, of the nutritionist, explains Noth-West University from South Africa. In theory, although water does not contain energy, if its temperature is low, the human body would use energy to maintain the basal temperature after it is consumed.

A thermogenesis effect would be induced. Several studies have been carried out in this regard, with the aim of elucidating whether this mechanism would be beneficial for weight loss: the results indicate that the caloric expenditure on thermogenesis is minimal or null.

Until the chewing gum has been included in this supposed negative calorie effect. But studies have once again banished the myth, as Nienaber-Rousseau comments: chewing burns 11 kcal per hour, and a stick of gum contains about 10 kcal; it would take an hour or more to chew to burn the same energy that chewing gum provides.

The mistake when it comes to losing weight

Although foods such as celery or cucumber do not have negative calories, they are always included in diets to lose weight. And in fact they tend to work, since the individuals who follow them lose weight. But it’s not because of the negative calories, as these three experts explain.

What actually happens is that these foods are very low in calories, but bulky, therefore they have a great satiating power without contributing a large number of calories to the body. Likewise, a little more physical activity is usually carried out when these types of diets are carried out. Both factors, taken together, end up leading to weight loss.

On the other hand, if the consumption of bulky foods such as celery, lettuce or broccoli is encouraged, also unhealthy foods are often avoided like fast food. It is another factor to take into account.

Is about various factors that should be part of the diet plan, consciously, but not through deceptions or fallacies: it is not about negative calories, but about healthy foods dense in nutrients but low in calories, while filling and displacing other undesirable foods.

In addition, experts explain, it is important to take into account this “substitution”: It is useless to add these foods to the diet without displacing those based on processed or ultra-processed, dense in calories and not very dense in nutrients. Otherwise, all you do is add calories to the diet, even if only in small numbers.

Although it is easy to explain, it is often difficult to do. As Nienaber-Rousseau explains, studies indicate that people tend to underestimate the energy content of meals when there is healthy food on the plate, even as a side dish. It is known as “the illusion of negative calories“. However, these so-called negative calories do not exist, and they are not a real weight loss aid.