What are calories?

‘Calorie’ is the term we use when we’re describing the energy we get from the food and drink we consume, as well as the energy we expend in our day-to-day activities. A calorie is a measurement, just like a gram or an ounce – it’s a simple measure of energy units (calories).


The term, calorie, is shorthand for kilocalorie, although you may also see the term kilojoules (KJ) used – this is the metric measure of a calorie. To convert a kilojoule to calories, simply divide the kilojoule figure by 4.2.

Visit our ‘All you need to know about diets’ page for recipes and more expert advice on weight loss, including low-GI and the Mediterranean diet’

Why is a healthy weight important?

Being overweight puts us at an increased risk of developing serious health problems, including heart disease and diabetes. The extra weight puts additional pressure on joints and makes it harder for us to exercise. You’re also more likely to suffer from sleep disturbances, such as sleep apnoea, which can make you increasingly tired and moody.

If you’re overweight, with a BMI greater than 25.0, losing 5-10% of your body weight can bring many benefits. Not only will you feel better and be able to move with more ease, you can expect improvements in your blood sugar control, experience less joint pain and lower your risk of chronic health conditions for later in life.

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Why are calories important?

Our bodies need calories even at rest. They keep us warm, fuel our activity, help maintain our general health and facilitate cell growth. When we eat food, it’s broken down to release energy as calories, which are either used by the body straight away or stored for later use, depending on our bodily needs. If we eat too many calories, on a consistent basis, it’s likely that we will gain weight.

How many calories do I need?

The number of calories we need varies and depends on our unique requirements, based on our age, gender, build (covering height and weight), activity levels, general state of health and even our genetics.

Your GP or health professional may have already given you a calorie goal. The following information is relevant for an average, moderately active, healthy person. However, be aware that these are estimates and not recommendations.

Children (7-10 years)

This is a period of rapid human growth and development. It’s also during these formative years that many dietary habits and attitudes to food are formed. Studies suggest that being overweight at this crucial life stage can have long-term implications for future health – for example, obese children are five times more likely to grow up to be obese adults.

While having high-calorie needs, this age group has high nutritional needs too. Any weight loss programme for a child should only be conducted under the supervision of a doctor or paediatric dietician. Failing to do so may mean your child missing out on crucial nutrients needed for growth and may put them at risk of developing unhealthy eating habits.

Daily calorie requirements to maintain weight:

Female: 1,530-1,936 kcal
Male: 1,649-2,032 kcal

Teenagers (18 years and under)

There’s a lot of physical change during these years, with growth spurts and hormonal shifts combined with higher levels of activity. Calorie and nutritional needs are significantly increased.

Daily calorie requirements to maintain weight:

Female: 2,223-2,462 kcal
Male: 2,414-3,155 kcal

Women (over 18 years)

Ever wonder what is the calorie intake for women? For women with a smaller body mass, lower levels of muscle and an average 6-11% higher body fat than men. Daily calories for women are generally lower. However, their nutritional needs are also greater, especially for micronutrients such as iron and calcium.

The age-old advice to ‘eat for two’ during pregnancy is sadly a myth, but there is an increased calorie need during the third trimester when an additional average of 200 kcal per day are necessary. (Actual calorie needs will depend on age, pre-pregnancy weight and activity levels.)

Daily calorie requirements to maintain weight:

2,000 kcal
Pregnancy, third trimester: 2,200 kcal

Men (over 18 years)

Men are typically taller and heavier than women. In a nutshell, their larger body size and greater muscle mass leaves them with a higher calorie need.

Daily calorie requirements to maintain weight:

2,500 kcal

Elderly (75 years and over)

As we age, we start to lose muscle mass and become less active. While our calorife needs fall, our need for other nutrients, such as protein, vitamins and minerals, remains unchanged or can even increase. Appetite levels tend to fall at this life stage, making nutrient-dense foods even more important. Women generally start to see this shift in their 50s, whereas for men it can be a decade later.

Daily calorie requirements to maintain weight:

Female: 1,840 kcal
Male: 2,294 kcal

How many calories to lose weight?

Ever wonder how to work out maintenance calories? The national guidelines recommend that for gradual weight loss, a reduction in calorie intake or an increase in activity levels equivalent to 500-600 kcal a day is required for a weekly weight loss of around 0.5kg (1lb). While this may be an effective way to kick-start your weight loss regime, it’s usually only helpful in the first few months, after which hormonal adaptations may hinder any further loss.

As research progresses we’re beginning to understand that the theory of ‘calories in and calories out’ is an over simplification of the way our body uses energy. There are many other factors at play, including the type of foods we eat, how we prepare these foods, our own basal metabolic rate and even the type of bacteria that live in our gut.

A variety of modern diets, featuring different macronutrient composition and calorie counts, have been assessed for their efficacy, and there is no best fit-for-all. The diet that is best for you will be the one that best fits your unique personal circumstances.

If you start to experience a plateau during your weight loss journey, try and incorporate more activity into your day. Studies suggest that optimum results are achieved when calorie restriction and a moderate walking programme are combined. Find out more about walking and its many health benefits.

How can I reduce my calorie intake?

Making a few savvy changes to how you eat can help cut the calories with minimal effort. Try:

• Reduce high-fat and high-sugar foods, such as drinks, fried foods, cakes, biscuits and desserts
• Choose leaner cuts of meat and trim away any excess fat before cooking
• Boil, steam, poach, grill or microwave rather than frying food
• Understand what a healthy portion size is and stick to it
• Moderate the amount of alcohol you consume, and when you do drink choose options with a lower sugar content

Explore our guides and recipe collections for more information on how to approach weight loss in a healthy, balanced way.

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Is calorie counting safe for everyone?

Ever wonder how to count calories? Although some people find counting calories an effective tool for weight loss, it may not be appropriate for us all, especially those with a history of disordered eating or an obsessive or unhealthy attitude towards food.

As with all restrictive diets, pregnant and breastfeeding women as well as diabetics and those on medication, should seek medical advice before embarking on any form of calorie restriction. This is especially relevant for teenagers, children and the elderly who may be at risk of missing out on crucial nutrients for growth and repair.

A few final thoughts

Some people find counting calories an effective way to quantify and manage their energy and achieve weight loss, at least in the short term. However, focusing on calories alone ignores the wider contribution food makes to our health and well-being.

If you are considering attempting any form of diet, please consult your GP first to ensure you can do so without risk to your health.


All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.

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