The Times Australia
The Times World News

.

how do we know the energy content of food, and how accurate are the labels?

  • Written by Lauren Ball, Professor of Community Health and Wellbeing, The University of Queensland
how do we know the energy content of food, and how accurate are the labels?

Everything we consume contains energy our bodies use to move, grow and maintain health. To work out how much energy is in different foods and drinks, we need to first look at a few core concepts.

Firstly, you’ve probably heard of the units of measurement for energy – calories – as well as the metric equivalent, which is joules. One calorie is defined as the amount of energy required to raise the temperature of 1 gram of water by 1℃.

In human nutrition, the amounts of energy needed to maintain health, and to fuel a body, are much larger than the tiny singular calories used to heat up a gram of water. So, the term “calorie” in nutrition commonly refers to a kilocalorie[1] (or kcal), which is 1,000 calories. When you see the word “calories” on a nutrition label, it’s likely referring to kcals.

The energy stored in food and drinks is released when the body breaks down one or more of the four macronutrients inside the food (carbohydrates, proteins, fats, alcohol). The body then uses that energy for activities such as keeping our heart beating, our lungs breathing and our muscles moving.

When energy in food is estimated, it is the amount of energy food and drinks provide for these bodily processes. The four macronutrients provide different amounts of energy[2]:

  1. 1 gram of carbohydrate provides about 4 kcal of energy
  2. 1 gram of fat provides about 9 kcal of energy
  3. 1 gram of protein provides about 4 kcal of energy
  4. 1 gram of alcohol provides about 7 kcal of energy.

How are calories estimated?

There are two ways to estimate the amount of energy in food and drinks.

The first is called “bomb calorimetry”. This gold-standard method involves placing a small sample of food or drink inside a device known as a bomb calorimeter. The food is burned in the presence of oxygen, releasing heat.

The amount of heat released is directly related to the amount of energy in the food, allowing a calculation to be made. This method is most commonly used for foods rich in fats and is considered the most reliable (but expensive) method.

The second method, the Atwater system, is a much less expensive method for estimating energy content. It is more commonly used when calculating energy of most food and drinks sold in supermarkets. Named after legendary food researcher Wilbur Atwater[3], this system uses a standard conversion factor for each macronutrient found in food and drinks. By estimating the amount of each of the four macronutrients, an approximate calculation of the total energy can be made.

However, this method requires detailed knowledge of the ingredients within composite foods (such as muesli bars or hamburgers) – which may reduce accuracy. There is also a margin of error to expect with the Atwater system, because it assumes each ingredient is always the same in composition.

For example, a cup of oats grown in one part of the country won’t necessarily have the exact same nutritional content as another cup of oats grown elsewhere, due to climate and soil differences. So, this system is an estimation based on an average.

Importantly, both methods estimate the amount of energy in food and drinks. But the actual energy our bodies extract from these foods and drinks can vary due to factors such as individual differences in digestion and absorption, as well as food processing and cooking methods.

Why do foods have calories written on them?

In Australia, it’s a legal requirement[4] for packaged food items to have a nutrition information panel that displays the number of kcal it contains.

However, homemade food items sold at places like a fresh market may not be required to provide a nutrition information panel. This will depend on the type of food being sold and the scale of the business operation.

Fresh foods such as fruit, vegetables and meat also don’t require a nutrition information panel. To find out the number of kcal in them, you can either run an experiment with a bomb calorimeter or look up an estimated value in an online nutrition database.

Food composition databases such as CalorieKing[5] compile information about the energy and nutrient content of various foods. Dietitians and other health professionals often use these databases to estimate the energy content of foods to inform dietary recommendations.

Different international standards

Both kJ and kcal refer to energy – they are just two different units of measurements (such as how inches and centimetres are two different units for measuring length). Kilojoules (kJ) is part of the International System of Units (SI).

Australia, New Zealand and some parts of Europe use kJ. The United States and the United Kingdom use kcal. To convert between calories and kilojoules you use the conversion factors:

  • 1 kcal = 4.184 kJ
  • 1 kJ = 0.24 kcal (about ¼).

For example, if you have a packet of chips with an energy content of 200 kcal, you can convert it to kJ as follows: 200 kcal × 4.184 = 836.8 kJ.

As for how many calories are acceptable to eat, the Australian Guidelines for Healthy Eating estimate the average adult requires about 7,000kJ or 1,670Kcal every day. However, differences in age, gender, size, health and physical activity will influence how much energy a person needs.

To estimate your personal energy requirements, you can use this nutrients and dietary energy calculator[6].

Read more: It's time to bust the 'calories in, calories out' weight-loss myth[7]

References

  1. ^ kilocalorie (www.sciencedirect.com)
  2. ^ different amounts of energy (www.sciencedirect.com)
  3. ^ Wilbur Atwater (www.sciencedirect.com)
  4. ^ legal requirement (www.foodstandards.gov.au)
  5. ^ CalorieKing (www.calorieking.com)
  6. ^ nutrients and dietary energy calculator (www.eatforhealth.gov.au)
  7. ^ It's time to bust the 'calories in, calories out' weight-loss myth (theconversation.com)

Read more https://theconversation.com/calories-and-kilojoules-how-do-we-know-the-energy-content-of-food-and-how-accurate-are-the-labels-211613

Times Magazine

Building a Strong Online Presence with Katoomba Web Design

Katoomba web design is more than just creating a website that looks good—it’s about building an online presence that reflects your brand, engages your audience, and drives results. For local businesses in the Blue Mountains, a well-designed website a...

September Sunset Polo

International Polo Tour To Bridge Historic Sport, Life-Changing Philanthropy, and Breath-Taking Beauty On Saturday, September 6th, history will be made as the International Polo Tour (IPT), a sports leader headquartered here in South Florida...

5 Ways Microsoft Fabric Simplifies Your Data Analytics Workflow

In today's data-driven world, businesses are constantly seeking ways to streamline their data analytics processes. The sheer volume and complexity of data can be overwhelming, often leading to bottlenecks and inefficiencies. Enter the innovative da...

7 Questions to Ask Before You Sign IT Support Companies in Sydney

Choosing an IT partner can feel like buying an insurance policy you hope you never need. The right choice keeps your team productive, your data safe, and your budget predictable. The wrong choice shows up as slow tickets, surprise bills, and risky sh...

Choosing the Right Legal Aid Lawyer in Sutherland Shire: Key Considerations

Legal aid services play an essential role in ensuring access to justice for all. For people in the Sutherland Shire who may not have the financial means to pay for private legal assistance, legal aid ensures that everyone has access to representa...

Watercolor vs. Oil vs. Digital: Which Medium Fits Your Pet's Personality?

When it comes to immortalizing your pet’s unique personality in art, choosing the right medium is essential. Each artistic medium, whether watercolor, oil, or digital, has distinct qualities that can bring out the spirit of your furry friend in dif...

The Times Features

How much money do you need to be happy? Here’s what the research says

Over the next decade, Elon Musk could become the world’s first trillionaire[1]. The Tesla board recently proposed a US$1 trillion (A$1.5 trillion) compensation plan, if Musk ca...

NSW has a new fashion sector strategy – but a sustainable industry needs a federally legislated response

The New South Wales government recently announced the launch of the NSW Fashion Sector Strategy, 2025–28[1]. The strategy, developed in partnership with the Australian Fashion ...

From Garden to Gift: Why Roses Make the Perfect Present

Think back to the last time you gave or received flowers. Chances are, roses were part of the bunch, or maybe they were the whole bunch.   Roses tend to leave an impression. Even ...

Do I have insomnia? 5 reasons why you might not

Even a single night of sleep trouble can feel distressing and lonely. You toss and turn, stare at the ceiling, and wonder how you’ll cope tomorrow. No wonder many people star...

Wedding Photography Trends You Need to Know (Before You Regret Your Album)

Your wedding album should be a timeless keepsake, not something you cringe at years later. Trends may come and go, but choosing the right wedding photography approach ensures your ...

Can you say no to your doctor using an AI scribe?

Doctors’ offices were once private. But increasingly, artificial intelligence (AI) scribes (also known as digital scribes) are listening in. These tools can record and trans...