Calorie Counting: Flawed Science

01/21/2021

Calories in, calories out. The diet industry is based upon this simple idea and currently, it defines the weight-loss strategy for hundreds of millions of people across the world. We are bombarded by advertisements, sport and health trainers, weight loss calculators, and calorie counting apps telling us to use this "science" as a way to improve our weight and health. But is this approach scientifically flawless?

The central idea behind calorie-restricted diets is self-evident, more energy (calories) use than energy entering your body equals weight loss. However, contemporary research shows that it is not that simple. Let me explain it to you.


Energy IN 

Energy-in is the number of calories consumed. A calorie is a unit of energy. It's a way of describing how much energy your body could get from eating or drinking. This would be the information that is available from food packaging or calorie trackers. However, in most countries, there is not a specific law about how accurate the information on the labels should be, and in the few ones that exist a regulation, the nutrition information on the food label can be legally off by up to 20% and still be considered compliant. So, the calories you see on the nutrition label may be quite different than what you're actually consuming. 

Even if we could accurately measure the calorific value of a meal, the relationship between those calories and our body is much less straightforward. The number of calories in food may not actually equal the number of calories you absorb from that food.  We know that the way that food is cooked alters its structure and therefore how much energy it provides. For example, a raw beef-steak tartare will provide fewer calories than a medium-rare cooked burger.  

Other factors that can affect your body's rates of absorption are: 

  • How food is processed 
  • The fiber content 
  • Gastrointestinal health state
  • Gut  bacteria (microbiome)

An example of this is corn. How the body uses and stores the energy gained from food as difficult to digest as corn on the cob is very different from how it uses energy from cornbread or from cornflakes processed (heated, pressured, and roasted).  To confuse things further, research shows that foods interact with each other, and their calorific content can vary when they mix. For example, the rate of energy released from a ham sandwich is different from the value of the bread and ham eaten separately at different times. Yet the simplistic calorie intake theory treats the energy gained from each case as the same.

Knowing all this, to calory count efficiently, you would need to cook every meal yourself from ingredients that you had weighed and measured with complete accuracy, considering the precise heat exposure of the food, and then eat an exact proportion of everything you cooked, and eat then separately!  As you can see, the idea that we can measure the energy value of any food precisely is nonsense.


Energy OUT

Energy-out is the energy consumed by the body. The process to determine the energy out is also far from simple. You have to take into account not only the physical activity,  but a combination of different factors like metabolic rate, the thermic effect of food, and the non-exercise thermal activity thermogenesis.


  • Physical Activity: This is our purposeful exercise like going to the gym, jogging, riding your bike, etc. The amount of energy expenditure is highly variable depending on the individual's unique activity levels.
  • Resting metabolic rate: This is the number of calories you burn each day simply at rest. This rate supports bodily functions like breathing, blood circulation, organ function, and brain function. This represents about 60% (the majority) of our energy output or "metabolism". The base metabolic rate can vary by 25 percent in normal, healthy people.
  • The Thermic Effect of Food: This is the amount of energy or calories required to eat, digest and absorb food. The amount of energy expenditure varies per macronutrient. For example, carbohydrates and fat require 5-15% of your energy output to digest, while protein requires 20-35%.
  • Non Exercise Activity Thermogenesis: These are the little unconscious things you do that use energy, like sitting up straight, moving your legs when sitting, touching your hair, etc. This makes up about 10-15% of your energy output.


To determinate scientifically metabolic rates researchers in human metabolism use a calorimeter chamber surrounded by sensors to measure the rate people use up oxygen and expelled carbon dioxide. This way they find the amount of energy that each person uses doing tasks like lying in bed, standing, or walking stairs. This precise technology is obviously not accessible to the general population. 

Additionally, there are some factors that determine strongly the rate that our bodies use calories, like genetics, age, gender, weight, and even our digestive health. Some people produce up to three times more starch-digesting enzymes (amylase) than other people, allowing them to break down starch and release more sugar far quicker. Another factor that can lead to a huge variation in our digestion is the make-up of our unique gut microbiomes. These microbes provide us with different abilities to digest food and convert the contents into energy. All these different variations between individuals in the amount and efficiency to metabolize food can have a big impact on how many calories our body absorbs and converts into energy. We can't ignore either how and when you eat the calories, and that different food of the same calorific value may have different metabolic effects on our body.

The assumption behind calorie-restricted diets is that everyone burns the same fuel in the exact same way and at exactly the same level of efficiency, however, this is a very simplistic a non very scientific way to understand how our bodies work. 


Misleading Calory Counting 

As we can see, even if we could quantify to some extent what energy goes into our bodies (that we have already established is extremely difficult), we have seen that it is not possible to determine what gets burnt off. 

And now you may think if calory counting is so imprecise, why is it so popular? Calorie counting gives us a false sense of control, security, and precision. It is a simplistic approach to a multifactorial and complicated subject as is weight loss. Additionally, psychologically calory counting can lead us to obsessive thoughts and over-worry about eating and food. This can precipitate eating disorders like orthorexia, characterized by an excessive preoccupation with eating healthy food. 

To summarize, if you are not an elite athlete or don't have to restrict your food intake due to a specific medical condition, don't take calorie counting too seriously. Use your time and energy to learn the benefits of a balanced diet and a healthy lifestyle. Enjoy your food following the principles of intuitive eating and relearning to listening to your body's natural hunger and satiety cues.


Let me help you to create a nutritional and lifestyle plan to achieve your health goals.