What is a calorie? The term calorie is commonly used as shorthand for kilocalorie and written as kcal on food packets. Calories are a measure of the amount of energy in food and by knowing how many calories are in our food can help us to balance the energy we put into our bodies with the energy we use, thereby keeping to a healthy weight. We measure the amount of energy contained in an item of food in calories, just as we measure the weight of that item of food in kilograms. If you’re trying to lose weight, it’s a good idea to eat less and be more active, even if you already have a balanced diet.
Within a healthy, balanced diet, a man needs around 2,500 a day to maintain his weight and a woman around 2,000 a day. These values can vary depending on age, metabolism and levels of physical activity, among other things.
Other factors to consider are:
- Growing children and teenagers may need more energy
- Your lifestyle and how active you are
- Your height and weight can affect how quickly you use energy
Also some factors affect how much energy you burn:
- Some hormones, the chemicals produced by the body, such as thyroid hormones
- Some medications, such as glucocorticoids, a type of steroid used to treat inflammation
- Generally being in poor health
- The amount of lean muscle mass you hold, lean muscle burns calories faster, even at rest
- The activities you do, for example a minute of running is rarely the same as a minute of cycling
- How much you push yourself in the activities you do, the more you sweat and struggle to catch a breath, the more calories you’ll be burning
A body builder or well-trained athlete may need three times as many calories as the ‘average’ person a day just to maintain their weight, that could be up to 6,000 calories for some athletes. Exercise builds muscle and muscle is the body’s most efficient calorie burner, therefore by keeping active can be a more efficient way to watch your weight, even walking the dog for 10 minutes longer each day or hoovering the stairs that bit more rigorously all counts. Your personal trainer can help with exercise programmes and calorie intake advice.
Knowing the calorie content of foods can be a useful tool when it comes to achieving or maintaining a healthy weight. It can help you to keep track of the amount of energy you are eating and drinking, and ensure you are not consuming too much. The calorie content of many foods is stated on the packaging in the nutrition label, which you will often find on the back or side of the packaging, under the “Energy” heading. The calorie content is given in kcals, which is short for “kilocalories”, and also in kJ, which is short for “kilojoules”. Kilojoules are the metric measurement of calories. To find the energy content in kilojoules, multiply the calorie figure by 4.2. The label will usually tell you how many calories are contained in 100 grams or 100 millilitres of the food or drink. Many labels will also state the number of calories in one portion of the food, always remember that the manufacturer’s idea of one portion may not be the same as yours and this could differ from the size of the portion you serve yourself.
Not all calories are the same, for example calories in processed sugar are digested quickly and can cause a surge in blood sugar levels, which then crash soon after eating, making us tired and hungry again. Whereas eating a diet rich in fibre will help you feel full for longer and so avoid over-eating. It is not simply the calorie count we consume that we have to think about, the type of food we eat can make a difference to our daily calorie intake too. Calories come from protein, carbohydrates and fat. Your personal trainer can advise you on a nutritional diet to suit your body needs taking in the appropriate ratio of protein, carbohydrates and fat calories.
We need calories to survive, without energy our cells would die, our hearts and lungs would stop, and if we consume just the number of calories our body needs each day, every day, we will probably enjoy happy and healthy lives but if our calorie consumption is too low or too high, we will eventually experience health complications.