A dieter’s worst nightmare. A burger with fries from Red Robbin Gourmet Burgers, Mike Gonzalez, CC-BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Red_Robin_burger.jpg

For the past couple of years, the idea that the calorie is the best representative of energy content in food and energy expenditure by the body has dominated nutritional thought. The debate on whether a ‘calorie is a calorie’ runs rampant in the comment section of many Instagram fitness pages, and is the central focus of many weight loss, gain and maintenance plans. Yet, strangely enough, when I began to ignore the caloric content in foods and focus on its nutritional value and metabolic properties, I lost 20kg.

To understand why this is, we need to understand the calorie’s scientific origins as well as the manner in which it fails to be the focal point of a balanced diet.


The calorie can be defined as ‘the amount of energy needed to raise the temperature of 1g of water by 1 degree Celsius and is equivalent to 4.186 joules. The calories you see on nutritional labels on various foods are determined in two ways:

· Using a bomb calorimeter: A bomb calorimeter is an apparatus that consists of a sealed container placed in water. The food is then placed in this sealed container and burnt, with the rise in temperature then being equated to the amount of calories present.

· Using the Atwater method: This method is premised on adding up the calories provided by the different energy containing components of foods, such as fats, carbohydrates and proteins. The caloric values of these components are usually stated in units of calories per gram, with these values being determined by burning each component and calculating an average.


The idea that ‘a calorie is a calorie’ was first proposed by Atwater, and describes the belief that a calorie is a sufficient means of describing the energy content of food as well as it’s effect on the body. My first encounter with this argument was in the Instagram’s fitness world, where many weight loss pages indicate that weight loss boils down to one simple equation:


I believe that this logic, whilst it may work for some, is based on the assumption that the human body is an isolated system, i.e., that it will treat the ingested foods the same way a bomb calorimeter would. Whilst an isolated system can be understood as one in which energy and mass remain constant, it could thus be tempting to say that by basing a weight loss plan on the notion above, that because there is an imbalance in calories in and calories out, that the body is not isolated as energy-in the form of fat- is being lost. However, if one considers that the logic is founded on experiments that were performed on an isolated system (a bomb calorimeter), with the logic then being transplanted on a system that does not react in the same way (the human body), I think the notion that the logic is flawed still holds, especially considering that your body, unlike the bomb calorimeter, does not actually burn the food.

In attempting to count calories in and calories out, one may fail to account for the manner in which the food is metabolised, and thus, the different levels of hunger and satiety they achieve. Consider a hypothetical thought experiment where your hunger can be numerically quantified, and you happen to be experiencing a hundred calories worth of hunger. You are given the choice between 100 calories of a fizzy drink and 100 calories of a complex carbohydrate such as sweet potato. If we stick strictly to our ‘a calorie is a calorie’ reasoning, today we decide to opt for the fizzy drink, because we are presented with the same energy content, but in different forms, and we accounted for this 100 calories on our calorie counting app, and we’re also craving the fizzy drink. What we do not know from making our decisions based on caloric content is that the body absorbs 30 calories of the fizzy drink per minute compared with 4 calories per minute from the complex carbohydrate, meaning that with our choice, we’ll be hungry for another 100 calories in 3 and a third minutes, but, if we judged the foods some of their other nutritional properties, and chose the sweet potato instead, we would only be hungry for another 100 calories in 25 minutes, which means we would be fuller for longer, and achieve the smaller portions we’re focusing on (without feeling hungry).

The calorie fails to account for the manner in which the body will respond to foods consumed by not taking into account yet another factor: insulin levels. Consider yet another hypothetical thought experiment: you are presented with 100g of fat and 100g of sugar. Armed with the knowledge that sugar contains less calories than fat, you opt for the 100g of sugar, as you believe it will ensure you adhere to your daily caloric deficit. By making this decision armed purely with caloric knowledge, you are not aware that the 100g of sugar you just ingested will prompt a spike in your insulin levels. High levels of insulin have been found to prevent the breakdown of fat in adipose tissue and facilitate the entry of glucose into adipose tissue, where it is converted to glycerol, and later, fat. So, despite our best intentions, we end up accumulating fat instead of shedding it.

The final manner in which the calorie has failed us is that it does not indicate how food will behave in out gut. Not only do individuals have vastly different gut microbiomes, which affects the breakdown of food, but we also have different gut lengths. Our final thought experiment: my gut is 4m long whilst yours is 8m long. This means that, compared to you, I have a shorter digesting time, with my body absorbing less calories from food than you, which mean’s you’ll likely be fuller for longer. We’re also the same weight, height, age and BMI, and we’re looking to lose the same amount of weight, so, our coach gives us the same caloric deficit, and we eat the same meals. This strategy fails to account for the manner in which our bodies digest the food: my shorter gut length means I could eat more but weigh less because I don’t absorb as much as of what I’m eating than you are. Granted, the calorie is a measure of energy, and we shouldn’t expect it to say all this, but by making it the master scheme of weight loss, we’re telling people that it does.

Bonus: calorie counting apps and watches don’t really account for the energy burnt digesting the food, with various food groups using up different amounts thereof, so you could be restricting yourself to the magical caloric allowance of 1200–1600 calories per day, when actually, you could be giving yourself a little more.


Many people praise the UK’s National Health Service, which even has weight loss plans on its website. However, a quick look at this 12 week plan reveals that it is premised on a daily caloric allowance of maximum 1400 calories for women and 1600 calories for men, without accounting for all our different builds and body types. It’s thus clear that, not only do we impress this notion on ourselves: one can see the manner in which governments also entrench this ‘calorie is a calorie’ notion in their citizens. I think the design of the calorie has good intentions, but the manner in which we treat it makes it one of the most misleading measures on nutrition labels. Maybe, instead of obsessing with Fitbit, we should ditch the processed stuff, and improve our relationship with food: I see a wonderful journey ahead.

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