What is a Calorie?

The food and drinks we consume provide our bodies with energy, which is measured in calories (or kilojoules, depending on which country you are in). We need energy (calories/kilojoules) to fuel our bodies.

A calorie is simply a unit of energy, a measure of how much energy is in the food and beverages that we consume.

When we think about calories it is important to remember that we don’t eat calories, we eat foods that contain calories.

The calories in our food, and listed on our food packaging, technically are kilocalories, although they are always referred to simply as calories - the amount of heat needed to raise the temperature of one kilogram of water by one degree Celsius.

Check out this helpful video by TED Ed:

What is a Kilojoule?

Kilojoules are just an alternative measure of food energy. In the same way that miles and kilometres are both measures of distance!

In Australia we use kilojoules to measure the energy content in foods. Well, technically we should, but most people still think about food energy in terms of calories, and you will generally find both calories and kilojoules on Australian food labels.

One calorie equals 4.2 kilojoules
One kilojoule equals 0.2 calories

Check out this helpful video about kilojoules. As you will see, they are the same concept as calories:

How Is The Energy (Calorie/Kilojoule) Content Of Food Measured?

Originally, the calorie content of a food was measured in a device called a bomb calorimeter. A known amount of food would be dehydrated to remove its water content, placed in a container with a set amount of water. The food was then - literally - set on fire until it is all burned off. The rise in temperature of the water indicated the calorie content of the food.

FUN FACT: Technically, a doughnut contains the same amount of energy as a stick of dynamite. So why don’t we explode when we eat a doughnut? That’s because the dynamites energy is released instantly (BOOM!) whilst the doughnut’s energy is released gradually as it is digested and absorbed.

The BOM Calorimeter was a good-enough method, but not completely accurate. For example, the fibre in foods would burn in the calorimeter but fibre is not burned as energy in our body! So these days, calorie content of foods are determined by the “Atwater indirect method”. Under the Atwater method, calorie content of different foods are calculated by adding up the calories provided by protein, carbohydrate, fat and alcohol. So each different food/meal is analysed to see how much protein, carbohydrate and fat it contains, and then the total energy is calculated using these values:

• Carbohydrate: 4 calories/17 kilojoules per gram

• Protein: 4 calories/17 kilojoules per gram

• Fat: 9 calories/37.7 kilojoules per gram

• Alcohol: 7 calories/29 kilojoules per gram

• Fibre: Any fibre content of the food is subtracted from the carbohydrate calculation due to the fact that our bodies don’t burn fibre for energy.

In the future, there is likely to be other more accurate methods of calculating calories as more is learned about how the human body burns food for fuel. For example, studies show that nuts have less calories than the amount calculated using the Atwater method, due to the fact that a portion of the fats in nuts is stored inside the nut’s cell walls and is not absorbed by our bodies.

How Much Energy Do I Need?

What Determines Our Energy Requirements?

How much energy (calories/kilojoules) you need to consume each day is dependent on how much energy you burn each day, which in turn is influenced by:

1. Your basal metabolic rate (BMR, or your basic metabolism): your body burns a lot of energy simply staying alive - your breathing, heartbeat, circulation etc. Your BMR is influenced by your height, weight, sex, age, body composition (more lean muscle mass means your body burns more energy) and your health status (growth, pregnancy and lactation burns more energy, as does recovering from serious illness)

2. The Thermic Effect of Food (TEF) aka your digestion: 10–15% of the calories we eat is used to fuel digestion.

3. Your Physical Activity Levels: how sedentary you are, how much deliberate and incidental physical activity you get.

How To Calculate Your Daily Energy Requirement

To calculate how much energy (calories/kilojoules) you need each day, you can calculate your EER (Estimated Energy Requirement). There are tables you can refer to (see https://www.nrv.gov.au/dietary-energy) but it is much easier to enter some details into a calculator, like these ones:

• https://www.eatforhealth.gov.au/webform/daily-energy-requirements-calculator

• https://www.healthier.qld.gov.au/tools/kilojoule-calculator/

Is Weight Simply A Function of Calories-In versus Calories-Out?

“Calories in/calories out” is valid - to an extent

So we need energy to fuel our bodily functions and all of the activities we engage in each day. But once these energy needs are met, any “extra” calories will be stored in our bodies. Some will be stored in our liver and muscles as glycogen, and the rest will be stored as - you guessed it! - FAT!

Calories-In-Calories-Out (CICO) or Energy-In-Energy-Out (EIEO) has for the last few decades been the method of choice for anyone wanting to lose weight, or maintain a healthy weight.

And studies do support its validity. The fact is, if you consistently take in a lot more energy than your body needs, you will indeed gain weight. Scientists actually refer to this as “Overnutrition”. And not only will chronic overnutrition cause you to gain weight, it will also place your body into a state of metabolic stress causing inflammation. Over time it can lead to blood sugar and insulin dysregulation, and the accumulation of toxic visceral adipose tissue around your organs, increasing your likelihood of developing heart disease, type 2 diabetes and even cancer.

And the flip side is that if you regularly burn more energy than you consume, you will lose weight.

Health is more than just “calories in/calories out”

While “calories/calories out” is relevant to weight loss and maintenance, not all calories are created equally from a health perspective, which in turn impacts our metabolism and weight.

That’s because the food we eat doesn’t just contain energy/calories. The foods we eat contain NUTRIENTS - substances that provide essential nourishment for our body’s growth and repair. Different foods have different impacts on various systems in our bodies, due to differing nutrient content. I wrote about nutrients HERE.

For example, regularly consuming high amounts of nutrient-bereft refined carbohydrates (like processed snack foods) may over time increase your inflammation levels and push you into insulin resistance, which will increase your body’s tendency to store fat.

Check out this helpful video which shows what 200 calories of different foods looks like:

So, should I count calories?

The amount of energy/calories you regularly consume versus the amount you regularly expend is definitely something I think we should all keep a healthy, non-obsessive eye on, especially if you find your weight creeping up (or down) over time. Remember, chronic overnutrition is a health-risk, so it is always a good idea to make sure you are not consistently burdening your body with more energy than it needs.

But if you focus only on the calorie content of the foods you eat, you are short-changing your health!

Not all calories are created equally. That’s because we don’t eat calories, we eat an area of different foods that contain calories. And the impacts of the foods we eat on our weight and our health go way beyond their calorie content. Not all low-calorie foods are healthy, and not all high calorie foods are unhealthy.

I highly recommend you check out a couple of posts that set out the things I believe we should be tracking to improve our health:

THIS POST sets out a few other things I recommend my clients consider when making their daily food choices.

THIS POST sets out my list of non-food things to count (or track) as you travel along your healthy happy journey.

Check them out!

REFERENCES

Novotny JA, Gebauer SK, Baer DJ. Discrepancy between the Atwater factor predicted and empirically measured energy values of almonds in human diets. The American journal of clinical nutrition. 2012 Aug 1;96(2):296-301.

Baer DJ, Gebauer SK, Novotny JA. Measured energy value of pistachios in the human diet. British journal of nutrition. 2012 Jan;107(1):120-5.