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What are calories?



In this article Barney St Anton discusses the subject of calories;

  • What calories are.
  • The concept of energy balance.
  • How to accurately estimate and adjust caloric intake for your goals.
  • Plus, useful tools that may help you along the way.

Contrary to the quotes you see on social media, calories are not little monsters that live in your wardrobe and sew your clothes a little tighter every night. In fact, there’s nothing scary about them at all!

What are calories?

You have likely come across calories when looking at food packaging. Found on a restaurant menu or even on the screens of the treadmill at your gym. However, you most likely do not know what a calorie actually is.

The scientific definition of a calorie is “the energy needed to raise the temperature of 1 gram of water by 1 °C”.

To put it simply, a calorie is unit of energy. Calories are the energy currency you require for growth, metabolism and other bodily functions. This occurs via complex metabolic processes involving various enzymes and hormones. Foods that contain calories are required in large amounts and are called ‘macronutrients’ (carbohydrates, fat, protein and alcohol), which we’ll learn more about in future articles.

Why are calories important for your goal?

Nutrition can at times be a confusing topic with various sources touting contradicting claims. For every ‘expert’ that preaches the benefits of a low carbohydrate ketogenic diet, there is another who supports an opposing approach.

The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet that in medicine is used mainly to treat hard-to-control epilepsy in children. The diet forces the body to burn fats rather than carbohydrates.

For many people it can be difficult selecting a dietary approach, often falling victim to the misinformed endorsements of celebrities or influencers. There is, however, one key concept that most people can understand and believe. To lose weight you need to eat less and move more, and the reverse will likely result in weight gain. The key factor that governs the success of every nutrition plan or diet is the relationship between calories in and calories out providing an ‘energy balance’.

Energy Balance

Energy balance occurs when your energy intake e.g. food and alcohol intake, perfectly match your energy expenditure. This means you physical activity and basal metabolism in particular. This means that you aren’t over or under eating but consuming just the right amount of energy for your current expenditure. If it were possible to maintain perfect energy balance, a near impossibility, you would remain roughly the same weight year after year. Daily fluctuations would occur due to factors such as water intake, the amount of food in your gut and the menstrual cycle.

Energy balance is the foundation of nutrition for body composition and has the biggest influence on dietary success. To improve body composition by losing body fat and/or gaining lean muscle mass, the number one priority of the nutrition programme should aim for energy balance.

Energy Intake

Energy intake refers to anything we consume that contains energy in the form of calories. This is influenced on a daily basis by intake of:

  • Food: starches, vegetables, fruit, meat, dairy and yummy stuff too
  • Beverages: fruit juices, milk, and alcohol for example

Throughout the rest of this article, we will discuss how you can alter your energy intake to achieve your goals.

Energy Expenditure

Energy expenditure refers to anything we do that uses energy in the form of calories. This is affected by some factors that can be easily altered such as physical activity and some that cannot be easily altered such as keeping warm i.e. thermal regulation, and basal metabolism.

Weight Loss and Gain

Negative Energy Balance leading to weight loss

Negative energy balance occurs when energy intake is lower than energy expenditure. This may be a result from restricted intake through dieting. An increase in physical activity, or a combination of activity and diet appears most effective. The result is an energy deficit that the body must overcome in order to function. The body utilises stored energy in the form of glycogen within fat & muscle tissue to supply the required energy. The breakdown of bodily tissue in this manner results in weight loss as those energy stores are utilised.

In healthy individual’s negative energy balance results in weight loss 

Positive Energy Balance leading to weight weight gain

Positive energy balance occurs when energy intake is higher than energy expenditure. This may result from increased intake or decreased physical activity. More often than not it is a combination of both. Epidemiologists use the term “Obesogenic environment” to describe how the Western world is perfectly set up for a desk-bound and inactive lifestyle with a diet that is rich in calories but deficient in nutrients. This creates an energy surplus with the excess energy being stored as fat, muscle or glycogen. This increases body tissue mass and so results in weight gain. 

In healthy individual’s positive energy balance results in weight gain

Adjusting Energy Balance for Your Goal

Setting realistic targets for weight loss is critical. You may have lofty goals to lose X amount of body fat weight in Y number of weeks. However, this is only achievable through unsustainable crash diet methods. As such, I strongly suggest starting with the aim of losing 1lb per week, treating any extra loss as a bonus. Whilst aiming to lose 1lb a week may not seem significant; such an approach ensures the majority of weight lost is fat and not lean mass compared with losing higher amounts in shorter time-frames. Given that 1lb of human body fat is equal to approximately 3,500 calories of energy, a deficit of 3,500 calories is needed to achieve the above. As there are 7 days in a week, we need to create a deficit of 500 calories per day.

Worked example:
Intake for -1lb/week = energy balance – 500
= 2,953 – 500
= 2,453 calories

Furthermore, I strongly suggest a slightly more conservative approach when looking to increase body mass in order to minimise accumulation of excess body fat. As a result, an energy surplus of just 1,750 calories per week, or 250 per day, is likely a reasonable starting point. Of course, this energy surplus could also be achieved by reducing physical activity, but this would be counter-productive for those aiming to improve muscle size.

Worked example: 
Intake for +0.5lb/week = energy balance + 250
= 2,953 + 250
= 3,203 calories

Tracking Calorie Intake

A simple and effective way to track calorie intake is through Apps such as MyFitnessPal. Using this App you can record your dietary intake by scanning bar codes, uploading recipes or searching the database to find popular household items. This will not only allow you to track your caloric intake, but it will also provide an insight into macro/micronutrient intake. Additionally, you will have the capacity to estimate physical activity expenditure as well. As you become more familiar with this process, look at food labels when you are shopping so you can make informed choices and find alternatives sources of food energy.

A Cautionary Note 

A cautionary note to keep in mind is that whilst calories are important, tracking caloric intake is not always conducive to a healthy relationship with food for some individuals. This doesn’t mean energy balance is any less important to the success of these individuals’ goals, but it should change the tools you use to help them achieve these goals.