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thermic foods

The Thermic Effect of Foods and “Negative Calorie Foods”

What if we told you that eating food burns calories? It’s true, your body expends energy to break down food. Of course, foods contribute more calories than they take to digest but that doesn’t mean that all foods are created equal. Some foods contain hardly any calories at all and may even contribute less than they require – although some experts aren’t convinced.

You probably won’t be able to lose weight by eating these “negative calorie foods” but it never hurts to incorporate more of them into your diet. Even if they don’t burn more calories than they provide, they provide a big nutritional bang for their buck.

Metabolism Boosting Foods

Metabolism and Diet

The constant use and storage of energy by your body is called metabolism. Your general metabolism describes how your unique body deals with energy. Some people have “slower” metabolisms that tend toward storing more energy and some people have a “faster” metabolism that tend toward burning more energy.

Part of this variance is genetic and related to the brain and body chemicals that play a role not only in how our bodies metabolize food but also in the ways that our brains and bodies crave food. A recurring trend in this article is that physical work is one changeable factor in our health. However, for many people, the fight for health isn’t just a physical conflict.

While we usually think of ourselves as burning energy through exercise, exercise only accounts for about thirty percent of total energy expenditure in the average person (Pope et al. 343). Granted, this number is significantly higher in the average HTBM reader, but this still goes to show that our bodies burn a lot of energy just by operating at a “basic” biological level.

The pace at which our bodies burn energy without doing much of anything at all is called the “basal metabolic rate” and makes up as much as sixty percent of the average person’s metabolism with the “thermic effect of food” making up a whopping ten percent (ibid.). Interestingly, this breakdown doesn’t vary in the same ways that other metabolic stats do.

Heat Transfer of Digestive Molecules

The thermic effect of food refers to the fact that digesting food requires energy. Just like different foods contribute different amounts of energy, different foods require different amounts of energy to digest. And, just like you can boost your net energy use by working out more, you can boost your net energy use by eating different foods.

Why Does Digestion Take Energy?

There are a number of reasons that digestion takes energy. Some play a bigger role than others.

The first of these has to do with cold foods and beverages. Whether or not your body “actively” heats up cold food and beverages is unclear. That a cold item dropped into a hot environment will warm is just physics. In the case of eating and drinking cold foods and beverages, this cools your body, which then must expend energy to return to its normal operating temperature.

Second, from teeth to toilet, eating and digesting and passing food is a muscular endeavor (Tortora et al. 888). Chewing and swallowing takes energy. Once in the stomach, food is mechanically digested by contractions of the stomach. Then, what’s left is passed through the intestines and out of the body – all of which requires muscular action.

Finally, digestion is also a chemical event. While digesting food often results in the storage of energy in the body (if more energy is consumed than used), breaking down that food also required energy at the chemical level. This is why, in the negative calorie foods list in the next section, the makeup of the food is taken so highly into consideration.

“Negative Calorie Foods”

Foods that require a lot of energy to digest and don’t release a lot of energy in digestion are called “thermic foods” or “negative calorie foods.” No food is actually a “negative calorie food” but foods that don’t have many calories can still require energy to digest, potentially resulting in a net loss of calories.

Now, recall that “calories” are different from “carbs.” As a culture we tend to use the term interchangeably. Carbohydrates produce a large number of calories, but calories also come from protein, fats and oils, and even alcohol.

So, what are some of these “negative calorie foods”?


An egg contains about 75 calories, but most of these calories come from protein. Some people go back and forth on eggs because they do contain fat but, considering everything else that they bring to the table, they’re a regular HTBM favorite.

You may remember eggs from our superfoods article. You may also notice that most of the foods from our superfoods article aren’t on our negative calorie foods list and most of the entries on our negative calorie foods list didn’t make the cut in our superfoods article.

Another HTBM favorite: Mushrooms


The nutritional value of mushrooms varies somewhat, but they generally have about fifteen calories per serving. They do bring some carbs to the table, but the carbs that they cary are about equal to the protein representation. Remember too that mushrooms also bring fiber and some valuable vitamins and minerals.


A cup of chopped celery has just fourteen calories. Crazy, right? All of those calories do come from carbs, but it’s just three grams per cup and all complex carbs. That’s the non-sugar kind that breaks down slowly to give you energy throughout the day.

You’ll notice that celery is the first entry on our negative calorie foods list that didn’t make the superfoods list. We’re not all that jazzed about the other nutrient offerings. They don’t contain many calories, and they’ll fill you with water and fiber, but they don’t bring along a lot of protein or anything like that. That’s kind of a trend for the rest of the foods on this list.

By the way, if you fill your celery stalk with peanut butter and raisins, it starts being delicious but stops being a negative calorie food.


A serving size of broccoli contains around thirty calories. Not the lowest number on this list, but not too shabby either. Most of those calories do come from carbs – about twice as much as in a serving of celery. However, broccoli also brings along fiber, a surprising amount of protein, and a selection of great vitamins and minerals including iron and potassium.


Cucumbers have just eight calories per serving while packing about twice as much fiber and about twice as much protein as broccoli. Their mineral representation isn’t as impressive, particularly not for weight lifters and body builders, but it’s nothing to sneeze at either.


Spinach has one less calorie per serving than cucumbers. Spinach also has a lot less protein. What does it bring instead? How about loads of calcium, iron, potassium, and other vitamins and minerals?


Lean meat has loads of calories. We’re talking about over 200 calories per serving. However, almost all of those calories come from protein. That’s why meat can make up such a huge portion of your net food intake on carb-restrive diets.

If we were to include lean meat on this list (and it’s a tough call) it would be less because it is low in calories and more because of where those calories come from. Further, from a sheer mechanical standpoint, meat is kind of a pain to digest, and that’s what costs calories. 

Is lean meat a calorie negative food, if there is such a thing? Probably not. But, to deliver all of those calories without any carbs and very little fat, it’s definitely something to think about.

On the fat note, we’re talking about lean meat here. If your burger is 40% fat, it’s not calorie negative – it’s health negative.

Other Lists and Other Foods

If you hunt out other lists of negative calorie foods, you’ll find different entries. Why? It is believed that one of the major contributing factors to the thermic effect of food is the water content of that food.

The result is that other lists prioritize foods with high water content, even if the foods have a high sugar content as well. We’re not buying it. Sure, heating water is a major consideration (a calorie is literally defined in terms of heating water). But is it a bigger consideration than sugar content? We don’t think so.

By the way, if you do believe that the most important thing to make a food calorie negative is the water content, just drink water. You should be drinking water anyway but if there is such a thing as a “negative calorie food” it’s definitely water – specifically cold water.

After all, some have argued that a lot of the calories spent in digesting food comes from chewing, but chewiness of food is seldom taken into consideration when compiling these lists, or gum would be at the top of all of them. Arguably, chewiness does take some place: we didn’t think of “chewiness” but we thought about fiber content.

Clean and Pure Supplements from Bulk Supplements

Should You Chase Negative Calorie Foods?

Yes. Yes you should.

We’re being honest: with the possible exceptions of water and sugar-free chewing gum, there might not be any actual “negative calorie foods” but that doesn’t mean that you shouldn’t be thinking about negative calorie foods.

Even if these foods don’t exist, thinking about them more and trying to incorporate more of them into your diet is a worthy endeavor.

The Journey Is the Worthier Part

This is definitely one of those “the destination is the journey” kind of articles. Experts are split on whether or not calorie negative foods even exist. You can believe in them, or you can think they’re a myth. You don’t need to believe in them to eat foods that are low in calories and high in nutrients.

Further Reading

Pope, Jamie; Nizielski, Steven; McCook, Alison. “Nutrition for a Changing World.” Macmillan Learning. New York, NY. 2015 
Tortora, Gerard J & Derrickson, Bryan. “Principles of Anatomy and Physiology.” 14 ed. Wiley. Hoboken NJ, USA. 2014.

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