Energy and Calories

We're publishing a series of posts on nutrition which we hope will be useful to those who are keen to find out more about what’s in the food we eat and how we can incorporate healthier options into our lifestyles. This week we’ll be kicking off the series with the energy balance and calories.

The Need for Energy

Our bodies need energy in order to function. We use up energy when breathing, eating, and even thinking! Whenever we eat or drink, we obtain energy from what we consume which is then used as ‘fuel’ for the body so that it can perform the necessary bodily processes to function properly.

Energy Intake and Expenditure

Energy intake comes from everything we consume and energy expenditure is based on physical activity. Weight gain occurs if energy intake is consistently greater than energy expenditure over a period of time because the excess energy is stored in the body as fat. On the other hand if energy intake is less than energy expenditure over a prolonged period of time, weight loss occurs. Body weight remains stable if the energy intake and expenditure is the same. So, if you happen to overeat on some days, this can be balanced out by consuming less on other days.

Energy Requirements

Various factors affect the amount of energy we need:

Size and shape
Height
Age
Amount of physical activity

It is important to know the calorie content of food to maintain a healthy weight. As a guide, the average man needs around 2500kcal (10500kJ) to maintain his weight, and the average woman needs 2000kcal (8400kJ). If you find that a single meal is more than 1000kcal it’s more or less half of your daily energy requirement - if you finish it! Therefore, your other meals throughout the day should be lighter so you are not at risk of consuming a surplus of calories which could result in weight gain further down the line.

Calories and Kilojoules

When talking about the amount of energy in food we use the term ‘calories’ and on food labelling you’ll almost always see this referred to as kilocalories or ‘kcal’. We get most of our calories from 3 key nutrients, also known as ‘macronutrients’.

Fat - 9 calories per gram of fat
Carbohydrates - 4 calories per gram of carbohydrate
Protein - 4 calories per gram of protein

If your goal is to lose a few pounds, it’s a good idea to reduce your fat intake as you can see that it is the most concentrated source of energy.Alcohol can also provide calories - 7 calories per gram of alcohol. However, it is not considered to be a nutrient as it is not required by the body for growth or repair.Kilojoules (kJ) are another form of measurement for food energy and you will also see this displayed alongside kcal on food labelling in the EU. Many other countries use either kcal or kJ and not both - in the US the kilojoule unit is rarely used. One kilojoule is equal to the calorie value multiplied by 4.2.

Maintaining Energy Levels

We all have days when we’re feeling a little slow and sluggish. Here are a few tips on the types of food that can help you get that extra spring in your step:

Opt for wholegrain foods such as oats, wheat, corn or wholemeal varieties of bread or pasta. These release energy slowly over time. Gluten free options include brown rice, quinoa or millet.
Eat more fruit and veg, some of which have natural sugars which can sustain your energy levels. What’s more, they tend to release energy gradually so they won’t cause a sugar crash. Examples include: red peppers, broccoli, apples, strawberries and cherries which are easy to snack on.
Eat iron-rich foods such as red meat, spinach and fortified breakfast cereals. Iron helps transport oxygen throughout the body and low levels can cause poor energy levels and fatigue.
Eat regularly and have around three main meals a day.