Calories & Macronutrients Explained

You’ve probably heard a lot about calories and macros when it comes to losing fat or achieving a body composition goal. But do you know what these actually are and the importance of them? Let us help break it down for you… 


Before we talk about macronutrients, aka “macros”, we have to first talk about calories. A calorie, as commonly referred to on food nutrition labels, is a unit of energy. More specifically, a calorie is the amount of energy it takes your body to raise 1 gram of water by 1 degree Celsius. For those of you new to the world of nutrition, it’s easier to think of a calorie as a measurement of the energy we need to fuel our bodies.

The total amount of calories a food contains is dependent on the macronutrients that make up that food (protein, carbohydrate and fat).


When you consume food, your body can do two things with the energy that it absorbs; burn it or store it. The calories are either used by the body to keep us alive and moving, or if they aren’t used, they are stored as chemical energy.

As you can imagine, this becomes fundamental when it comes to managing your body weight. To put it simply:

  1. If you burn more calories than you eat you will lose weight (calorie deficit)
  2. If you eat more calories than you burn you will gain weight (calorie surplus)
  3. If you eat the same amount of calories that you burn your weight will remain the same (calorie maintenance)

Once you know how many calories you personally burn in a day (you can use a TDEE calculator to work this out) you can calculate how many calories you need to eat each day in order to achieve your body composition goal – whether it be weight loss or weight gain.


Macronutrients are nutrients that are required in large amounts to provide the energy needed to maintain body functions and carry out the activities of daily life. There are three main macronutrients – protein, carbohydrate and fat – which are molecules contained in different amounts in all food and beverages. Each of these molecules have a corresponding caloric value which give the total caloric value of the food:

  • Protein = 4 calories per 1 gram
  • Carbohydrate = 4 calories per 1 gram
  • Fat = 9 calories per 1 gram
  • Alcohol = 7 calories per 1 gram

This information can be found on the nutritional label on the food or via a food tracking app or nutrition data website.


Proteins are the primary building blocks of our bodies. They are used to build tissues like muscle, tendons, organs, and skin, as well as many other molecules that are essential to life such as hormones, enzymes, and various brain chemicals. Numerous studies have shown that a high protein diet has major benefits for muscle gain, fat loss and metabolic health. It is essential for building muscle, maximising muscle retention when dieting and also helps you feel fuller for longer.


Carbs are the body’s primary fuel source. They allow our heart, lungs, kidneys, brain and muscles to function properly. Carbs are particularly important to fuel the brain, helping us to think clearly and to balance our mood, as well as to enable our muscles to work effectively during exercise. They also prevent protein from being used as an energy source and enable fat metabolism. Sources of carbs such as starchy foods, vegetables, fruits, legumes and dairy products are an important source of fibre and nutrients such as calcium, iron, and B vitamins.


Fat is a vital source of essential fatty acids that our bodies cannot produce and has many important roles in the body including providing energy, maintaining healthy skin and tissues, proper functioning of our nerves and brain, absorption of vitamins, and hormone health. In addition to all of these important physiological functions, fat in our diet can also help us to feel fuller for longer which can make the dieting process easier.


By tracking your calories alone, you can influence your body weight, but not so much your body composition (muscle to fat ratio). In other words, you’ll just become a smaller or larger version of yourself without looking significantly leaner or more muscular.

By taking it a step further and tracking your macronutrients (in particular your protein intake), you can specifically target improvements in your body composition. Eg. you can target fat loss or muscle gain as opposed to just weight loss or weight gain.

This is what is going to result in a more significant visual change in your body, especially when in conjunction with a resistance-based training program.

Want to achieve your body composition using effective, science-based methods? Click here to find out more about our Personalised Coaching.

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