This dieting concept sounds so good you really do want to believe it’s true.
That is, the idea of negative calorie foods…
Basically, some foods require more energy to digest than the calories contained within the food, and so eating them will help you lose weight.
Citrus fruits and celery have both basked in this flattering light down through the years. But, you may have heard anything from cabbage to spinach to grapefruit being called a negative calorie food.
Let’s take celery as an example.
It’s pretty much empty from a nutritional standpoint, made up of water, sodium, some nutrients, and fiber (cellulose). A large stalk of celery contains about 10 calories.
So, negative calorie advocates claim that the process of chewing and digesting this stalk of celery requires more energy than the calories contained in the celery, which means it has negative calories.
Sounds like a win-win option, but is there any substance to this theory?
Unfortunately, this is another of those silly nutrition myths that gets tossed about as truth, but has a severe lack of scientific backing.
Main Issues With The Negative Calorie Theory
There are some important flaws to bear in mind when thinking about this whole idea of negative calories.
Firstly, the theory is far too simplistic.
The digestive system obviously needs calories for fuel, however the calories your body burns for digestion are minuscule compared with the calories in the food itself.
Here’s a breakdown of the 3 factors which have an impact on energy expenditure (EE), to emphasize my point further;
- Thermic Effect of Food (10% of EE): the number of calories required to digest, absorb, transport, and store food.
- Basal Metabolic Rate (60-70% of EE): the number of calories the body needs to maintain body functions at rest.
- Physical Activity (20-30% of EE): the number of calories expended during daily activity and exercise.
As you can see, your body only uses 10 percent of the calories you take in across a whole day, to fuel digestion, and store nutrients from the foods you eat.
If we take celery as our
scapegoat example again, it is true to say that it’s low in calories.
But, it’s an awful leap to say that the body burns more calories chewing and digesting foods like celery, simply because they are a bit more difficult to digest than other foods.
There’s just no evidence of this being the case.
Food List Is Nonsensical
I find it difficult to get my head around this list of so-called negative calorie foods.
In fact, I really cannot say why they have been dubbed as such, other than that they all have a relatively high water and cellulose content;
- Beet Root
- Hot Chili
- Garden cress
- Green Beans
Fruit Cannot Be A Negative Calorie Food
Including fruit in this list of negative calorie foods, is extremely confusing.
Typically fruit does contain a lot of water, with some indigestible fiber. But, it is also very high in natural sugars.
Just to be clear, there are natural sugars contained in vegetables, too, but for the most part, this is less than that contained in fruit.
Anyhow, suggesting you will burn more calories digesting fruit, than the calories present in the fruit, is complete nonsense.
A one cup serving of raspberries, for example, has 64 calories, 14.7g carbs and 5.4g sugar. One cup of watermelon has 46 calories, 11.5g carbs and 9.4g sugar.
While the calorie content of these fruits are certainly low, there is no way your body is going to burn in excess of 64 calories (or 46 calories in the case of the watermelon) simply by digesting these fruits.
This notion defies bio-chemistry, and the Laws of Thermodynamics.
The Lowdown on Negative Calorie Foods
The idea of negative calorie foods is based on very little scientific evidence.
Fruits and vegetables are indeed low in calories, high in antioxidants, vitamins, minerals and phytochemicals, and they are also very filling, so obviously a diet rich in these foods is a good thing, and will help you to lose or maintain your weight.
But, in terms of putting you into a magical negative calorie zone, don’t hold your breath!
Boost Your Metabolism Naturally With Diet
There are a number of ways to boost your metabolism, and these tips are more than just some notion.
(Obviously, exercise is another way, particularly through building muscle, which is more metabolically demanding than fat, but I want to focus on what we eat and drink, for the purposes of this article.)
1. Regular Meals
There is evidence that an irregular meal frequency may lead to weight gain.
Researchers compared the effect of eating anywhere from 3 to 9 meals per day, and found that;
Irregular meal frequency led to a lower postprandial energy expenditure compared with the regular meal frequency, while the mean energy intake was not significantly different between the two. The reduced TEF (thermic effect of food) with the irregular meal frequency may lead to weight gain in the long term.
Protein is often discussed in relation to weight loss for its satiating ability.
But, studies also show it has thermogenic fat burning characteristics. One study concluded;
There is convincing evidence that a higher protein intake increases thermogenesis and satiety compared to diets of lower protein content. The weight of evidence also suggests that high protein meals lead to a reduced subsequent energy intake.
Another study found that thermogenesis was significantly higher after consumption of the protein-rich meal in comparison to a fat-rich meal;
The results indicate that DIT (diet-induced thermogenesis) is higher after protein intake than after fat intake in both lean and obese participants.
3. Spicy Foods
It might sound like another quack recommendation, but there is at least some evidence to support this idea, too.
Researchers have found that spicy foods, like chili pepper, mustard, cinnamon, ginger, ginseng, guarana, and turmeric may have an effect on metabolism.
One study on Thai women concluded;
Within 30 min after consumption of 5 g of Capsicum frutescens, plasma glucose level during the absorption period was significantly inhibited. The metabolic rate was also immediately increased after ingestion and sustained up to 30 min.
We often say that drinking water aids weight loss, but is there any proof?
Well, one study found that water consumption increased metabolic rate by as much as 30%;
Drinking 2 liters of water per day would augment energy expenditure by approximately 400 kJ. Therefore, the thermogenic effect of water should be considered when estimating energy expenditure, particularly during weight loss programs.
They suggest that up to 40% of this increase in calorie burn was the result of the body attempting to heat the water, which is probably why ‘ice cold’ water is bandied about as an aid to weight loss.
What are your thoughts on negative calorie foods?