Try to imagine this for a second: Picture a food that burns more calories than it provides. In essence, this food would allow you to lose weight just by eating it! That’s exactly the claim made about a class of foods that have come to be called “negative calorie foods.”
These foods, with celery as their poster-child, have been promoted throughout the fitness industry and are a key component of many diets. According to proponents, these negative calorie foods are extremely high in fiber but very low in calories. Since chewing and digesting food uses calories, the logic goes, these foods make your body burn more calories than they provide.
But, is there actual science to back this up? Do these foods live up to the hype or are they just another fitness myth?
A Look At The Science
It is absolutely true that your body uses fuel to chew, breakdown and absorb all the components of the food you eat. But the amount of energy used for this purpose is extremely low, only accounting for about five to ten percent of your daily caloric expenditure, according to the Mayo Clinic.
The fact remains, though, that it is possible for negative calorie foods to exist in theory, at least. There is no real science that proves that any food requires more calories to digest than it actually provides. Basically, there is no proof that negative calorie foods work. And, with the prevalence of this concept, it would stand to reason that if this were a provable fact there would be studies to back the claims by this point.
But there’s a very real danger associated with belief in negative calorie foods. When people are told grapefruit is a negative calorie food, for example, they usually do one of two things. Either they restrict their diet to an extreme and impractical degree, so that they are eating nothing but grapefruit or they try to work grapefruit in to every meal. The thinking behind this second approach is that the negative calories in the grapefruit will, like a black hole; suck up all the excess calories from the rest of their diet.
Let’s look at these two techniques individually to understand their full impact.
- Just Short Of Starving – This first method, of only eating negative calorie foods, amounts to starving yourself. To be sure, you will lose weight and you will lose it very quickly. But this rapid weight loss is extremely unhealthy. Not only is this type of restrictive diet denying your body the fuel it needs to perform all of the necessary functions that keep you alive, but it’s also lacking vital vitamins and minerals. Eventually, these extreme diets will likely backfire but forcing your body into starvation mode. At this point, you still begin to store fat instead of burning it and your body will turn on its own muscles for fuel.
- Self-Deception – Adding these negative calorie foods to a meal isn’t inherently bad for you. In fact, many of these foods are extremely healthy and should be eaten regularly. The problem is that this myth has had a negative connotation towards peoples’ perception of their meals. A 2010 study for Northwestern University tested how a healthy side can change the way that people see their meals. The subjects were given a bowl of chili and asked to estimate how many calories it contained. They guessed 699 calories. The test was repeated again but, this time, with a side of green beans. Somehow, in the subjects mind, the entire meal now lost calories and only contained 656 calories. Of course, the beans probably didn’t add many more calories to the meal. They most definitely did not, however, take calories away from the chili.
The bottom line, then, is that there is no basis for the belief in negative calorie foods. This is not a complete harmless misunderstanding, however. When people make dietary decisions under the guidance of this type of misinformation, they could be putting themselves at risk for some serious health conditions. Instead of following any sort of overly-restrictive diet, the sound advice is to practice moderation.
Your body needs a wide variety of nutrients that are found in a rich assortment of foods so you should never feel as though you can only choose from a small selection. Of course, you should try to stick to whole grains, lean meats skim products, unsaturated fats, and minimally processed foods but don’t go overboard. If you don’t enjoy a dietary lifestyle, you aren’t going to stick with it for any considerable length of time. And, ultimately, the healthiest changes you can make to your diet will last for years and support a happy, active life.