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The Calorie Myth

Rachel Lett, RNutr

Chief Care Officer


Body weight is an important biomarker for health. This is especially true for type 2 diabetes as excess body fat is contributing factor for metabolic syndrome. A common belief is that 'fatness' or 'thinness' is directly related to energy (calorie) balance. In other words, health is based on weight, and weight is based on energy balance.

The logic is simple. To maintain a stable weight, you must put in, exactly what you put out. So, if you eat more energy than you expend, you will gain weight. Equally, if you want to lose weight, you need to either eat less and/or exercise more so that you are in a calorie deficit. Based on the law of thermodynamics, the rationale makes sense — energy in must equal energy out.

Let's take a closer look at calories

A calorie is a unit of energy. More precisely, the amount of energy required to heat 1 gram of water by 1 degree celsius. In the 1800's, a man called Wilbur Atwater experimented by burning food in a chamber, that was submerged in a vat of water. He noted that different foods elicit different water temperatures, and thus calories.

From his workings, we understand that 1 gram of carbohydrate is 4 calories; 1 gram of protein is 4 calories and 1 gram of fat is 9 calories. To this day, we use this information to calculate the total calorie content of food and decide whether or not it is healthy —  in the eye's of modern day society, the lower the calories, the better.

Health is centered around calories —  you'll find it highlighted with utmost importance on food packaging and restaurant menus. It goes without saying that Atwater's research has made a lasting and impressive mark on nutrition — 'burn' calories, anyone?!

But why and how has this happened?

If you take a closer look, you'll notice that his findings are exclusively based on an apparatus, not a human body. This assumes that a calorie of carbohydrate, is the same as a calorie fat or protein and that calories respond exactly the same in every individual; just like an apparatus.

Our view of calories is over simplified and doesn't take into account the complexity of the human body OR the fact that we're all 'one of a kind', with a unique response to food. Your personal make-up of hormones, microbes and genes will dictate your response to calories (fat, carbohydrates and protein).

As Tim Spector showed in his Predict 1 study, even identical twins who share the same genes, respond differently to the exact same meal of muffins and a milkshake— one twin maintained a normal level of blood glucose and lipids, while the other twin had elevated levels of blood glucose and lipids. Consequently, one twin will find it harder to maintain a healthy weight, despite eating the very same calories as her identical sibling. This goes to show that hormones and microbes play a huge part in weight management.

A calorie is a calorie, right? Wrong

Fats, proteins and carbohydrates all provide energy, so indeed, they are calories. However, a calorie of carbohydrate is very different to calorie of protein. It's misleading to blanket fats, protein and carbohydrates as the same thing, as calories are just one factor of macronutrients.

If you think of it this way, distance is just one factor of a journey — cycling a mile uphill, is very different to a mile downhill. Your input into cycling uphill will be far greater than downhill, and you will indeed, 'burn' more calories! The devil is in the detail, and quality is key.

We know that protein and fat are essential nutrients and we need to eat these. They are integral for normal cell functioning —they service our bodies and keep us in tip top shape. Carbohydrates on the other hand are not essential. We are not required to eat carbohydrates as we can synthesis glucose as and when we need. The fact that protein and fat vastly contribute to health is just one consideration when choosing where you get your calories from. The next is understanding how different macronutrients effect weight and metabolism.

Going against the grain

Fats, protein and carbohydrates are metabolised differently, and influence 'fatness' independent of calorie consumption.

For instance, if you were to eat 500 calories of carbohydrate, your blood glucose and insulin would rise. Insulin promotes fat storage and inhibits energy liberation. In other words, insulin prevents weight loss.

On the other hand, if you were to eat 500 calories of protein or fat, blood glucose and insulin would not rise. The absence of insulin promotes energy liberation and weight loss. As you can see, what we eat effects our hormones, and hormones play an integral role in whether or not we gain weight.

Eating the right calories from the right kind of foods can also boost metabolism. A low-carbohydrate, moderate protein and high fat diet has been shown to increase muscle mass and mitochondrial expression. Mitochondria are the engines of our cell that use energy. Greater muscle cells and mitochondria means greater energy demand and thus a higher metabolism — meaning 500 calories will be used more efficiently and faster, resulting in an energy deficit. So in fact, eating the right diet and foods will improve your metabolism, and allow you to eat more calories.

However, with that said, calorie intake is never normally an issue with a low-carb diet. This way of eating is rich in nutrient dense fat and protein that invariably leads to satiety and a controlled appetite — you won't even want the extra calories that you could have.

Think of quality, not quantity

As you can see, one calorie is not the same as another — the quality of your calories matters, and has a huge effect on hunger, hormones and energy expenditure. We need to move away from calorie counting as a tool for weight loss and health, and instead focus on food quality. We're all different, so tune into your unique response to different foods. How do you do this? Experiment and test! A low carb diet is a good place to start. It will nourish your cells, increase metabolism, reduce insulin and balance hormones. Try it out for yourself and see if moving away from carbohydrates leads to natural weight loss and better health, independent of calorie counting.

Like what you’re hearing?

Stay tuned for more guides, to help you with your health journey.

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Take care 👋Rachel

I’m sure you’re curious about the science behind all this 🔬 Here are some recent medical publications about this topic:

And some books...
The calorie myth by Jonathan Bailor
The diet myth by Tim Spector

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