The topic of calories is one that brings a lot of confusion and dispute. Misunderstanding of this subject can lead to poor health choices. Smart application of the relationship between calories and health, however, can provide many benefits.
Before we take a deeper look at what I call ‘the calorie trap’, let's get our head around some basics…
Why do we eat food?
We eat food for many reasons: it provides essential nutrients which allow for the proper functioning of our body systems, and it provides energy for movement, growth, and repair. Food also plays a fundamental role in regulating our immune systems, reducing risk of injury and disease, as well as influencing mental health, cognition, emotion.
Food, and therefore nutrition, plays a key role in health.
This is why we have developed ways to track food consumption, because it allows us to gauge whether we are meeting our nutrient and energy needs, and therefore fostering good health.
This is where calories come into play… So, what exactly are calories?
In the context of nutrition, calories are a measure of the amount of energy within a given quantity of food. One calorie (technically a kilocalorie – which is why we see ‘kcal’ on food labels) is the amount of heat required to raise the temperature of 1 kg of water by 1°C.
Tracking the caloric content of our food therefore allows us to estimate the amount of energy we consume. When combined with an estimate of the amount of energy we spend in a day (also measured in calories), this allows us to get an idea of the amount of energy left over at the end of the day. If you consume more calories than you spend, you’re left with a surplus, and if you spend more calories than you consume, you’re left with a deficit. Surplus energy is stored in adipose (fat) tissue, and leads to weight gain, whereas a deficit of energy requires stored energy to be used up, leading to weight loss.
That’s the whole idea of calories. Calorie surplus = weight gain. Calorie deficit = weight loss. It’s sound science (based on simple physics) and is a pretty simple idea to understand. So, ever since the 70s, public understanding and use of calories has been increasing, to the point that today it influences nearly every food and exercise decision some people make.
So, what is the calorie trap?
It’s very easy to fall into the habit of using calories as the primary metric by which you measure health, and once the habit is adopted, other factors of good health are often forgotten about or underappreciated. Alternatively, someone may still be aware of the other important factors but care so much about calories that they will prioritise them when making food decisions. Either way, the diet gets shaped by calories, not by quality, and over time, caloric content becomes synonymous with its healthiness. This is what I call the calorie trap.
This is a problem because the method of using calories to measure health is flawed, for many reasons…
First of all, whilst the science behind energy balance is undeniable, calorie counting is an imperfect method of calculating it. In other words, the principle is sound, but the practical application of this idea brings complexity and confusion, making it difficult to put into practice. Let me try to explain why…
Calories eaten does NOT always equal calories absorbed. Our bodies are shaped like a tube; food enters the mouth and travels through this tube (AKA the digestive system) then is excreted out the other end as faeces. Only when food crosses the border into the body is it actually absorbed – and only absorbed food counts as calories. This is important because, whilst the digestive system is very efficient at extracting and absorbing nutrients, a small amount can remain in the tube and exit with the faeces. This is especially true in individuals with gastrointestinal disorders. This is also influenced by the state of our microbiome – which itself is influenced by our diet. Ultimately, this means that our estimated caloric intake may be incorrect (unless you want to dissect and analyse your poo).
Processed food provides more energy. When we think of processed foods we think of fast/junk food, but the term food processing actually refers to any modification that happens to the food after leaving the farm (processed foods have just undergone LOTS of processing, giving them their name). Processing covers everything from cutting to cooking to mashing, and partially breaks down the food. This means that when you eat it, some of the job is already done for you. As a result, more processed foods require less energy to digest. Take a raw vs cooked potato – both contain the same number of calories, however, the cooked one has undergone a change whereby the carbohydrate structures are partially broken down, and so require less energy to digest. This means that whilst the number of calories you consume is the same, the amount of energy you spend digesting them is different. Essentially, energy balance is not only affected by the caloric content of the food, but also by the state in which that food is eaten.
Different nutrients impact our metabolism differently. Once absorbed, different types of protein, carbohydrates, fats, vitamins, minerals, and various plant chemicals all have distinct actions in the body. These different nutrients have varying impacts on metabolic rate, appetite, behaviour, mood, digestion, sleep – and many other factors. This is important because through altering these factors, nutrients can either ramp up or turn down food consumption as well as ramp up or turn down energy expenditure. Caffeine for example, is a highly ‘bioactive’ plant compound that influences energy intake by modulating digestion, appetite, and behaviour, and has been shown to increase energy expenditure by boosting metabolic activity. This doesn’t mean caffeine directly leads to weight-loss, it just highlights that certain foods have distinct effects on energy – and when you collate all those distinct effects from all the different nutrients… it gets complex.
There are many other factors that make calorie counting an imperfect measure of energy balance (autoregulatory changes in resting metabolic rate, consumer calorie estimates are often inaccurate, errors and bias in food composition analysis, environmental factors influence nutrient density). So, even though the “energy in Vs energy out” theory still holds true – it is the practical, everyday implications of this equation that make it complex and often unreliable.
There is another reason why the method of using calories to measure health is flawed. If we look back to WHY we eat food, we see that food plays many important roles – only one of which involves energy. However, for many people, calories have become a representation of health itself – rather than just one small part of it.
Let me ask you this: if a low calorie brownie has 87kcal, and a banana has 105kcal... which would you choose as a snack?
You’d be surprised how many people would choose the brownie simply because it has fewer calories. However, this is part of the calorie trap as a banana offers more dietary fibre, minerals, vitamins, and phytonutrients. And a question of price… that brownie costs 89p, I can buy a fair-trade, organic banana for less than 40p.
Why does this belief of calories as a representation of health still pervade? There are a number of reasons… 1) there is a clear link to health since energy surpluses can lead to obesity and its associated health risks. 2) it is a relatively logical and straightforward concept to get your head around (in comparison to understanding micronutrient content, for example). 3) a ‘beach body’ and self-image centered culture fosters overdependence on the caloric content of foods. 4) companies can make a lot of money from selling low-calorie foods, meaning it works in their favour if calories are viewed as the be-all and end-all.
When all is said and done, considering calories is still the most effective way to measure energy intake and expenditure – therefore there are times when it is worthwhile using. Athletes training for an event, for example, should track their calories in order to maximise training and recovery. Even in non-athletes, perhaps it could be beneficial to spend a small period of time better understanding the energy content of different foods, so they can make informed choices. However, no matter the person, time, or reason, caloric content of food should never be the only variable considered. Fostering genuine health, after all, is critical to longevity, mental health, as well as a sustainable planet.
I give calorie counting 5/10.
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