Calories— some of us try to count them, far too many of us miserably try to cut them, and the majority of us unknowingly consume huge numbers of them. Knowledge is power, and whether you’re trying to lose fat, gain muscle, or simply maintain your current weight, being aware of how many calories to aim to consume is one of the keys to long-term success. So, exactly how many are we meant to consume? Our resident dietitian Nicky investigates.
What is a calorie?
A calorie (or kilocalorie) is simply a unit of energy. To put it in even more scientific terms, a calorie is the amount of energy or heat needed to raise the temperature of 1 gram of water by one degree Celsius. We tend to associate calories with food, however calories apply to anything containing energy, from a gas to a burger.
(In metric systems, the calorie it has been replaced by the kilojoule. 1 calorie = 4.186 kilojoules).
Why do we need calories (energy)?
Energy is not a nutrient. It is required, however, by the body for EVERYTHING including metabolic processes, physiological functions, muscular activity, heat production and the growth, repair, and maintenance, of new tissues. Every single process in the body requires energy. Our body’s main sources of energy come from the nutrients in our food, including carbohydrates, proteins, fats, and (on every day except perhaps Friday and Saturday) to a smaller extent from alcohol. Foods are a combination of these three macronutrients.
1g of carbohydrates = 4 calories
1g of protein = 4 calories
1g of fat = 9 calories
1g of alcohol = 7 calories
What affects how many calories I should consume?
The amount of calories you need to consume is influenced by several different factors including your age, gender, height, lifestage, health & training goals, physical activity levels and overall health.
Resting metabolic rate (RMR):
This represents the minimum amount of energy needed to maintain basic bodily functions including maintaining body temperature, heart beat and respiratory rate i.e. how many calories you body would burn if you were to do nothing but completely rest. RMR represents about 60-70% of daily caloric needs and reflects the amount of lean mass (muscle + soft tissue + fluid) you have. The higher your lean mass, the higher your RMR is. It is therefore important to maintain lean mass by not overly restricting calories or over-exercising when you are trying to lose weight.
Physical activity is one of the most important determinants when it comes to energy intake and includes everything from making your bed, lifting weights at the gym, bending over to hang washing and moving around at work. The more physical activity you engage in, the higher your energy requirements are. Physical activity and exercise raise your resting metabolic rate (RMR).
Health & Training goals:
How many calories you will need to consume is dependent on your goals- are you trying to lose fat or gain muscle? These are essentially two opposing processes as one requires an energy deficit and one requires an energy surplus. An individuals estimated daily energy requirements will vary depending on whether they are trying to lose, maintain or gain weight.
During periods of rapid growth and weight gain such as during childhood, adolescence and pregnancy, extra energy is required to create and maintain new cells and tissues. The elderly are generally far less physically active and have a much lower lean mass meaning that your grandma or grandpa probably don’t need to be eating anywhere near as much as you.
During times of illness, whether it be acute such as a common cold or flu, or chronic such as inflammatory bowel disease or cancer, energy requirements are increased in order to help repair the body’s tissues, strengthen the immune system and combat inflammation.
Does it matter where my calories come from?
Hell yes it does, and anyone who tells you a calorie is a calorie needs a wake up call. A calorie from protein, fat, carbohydrate and alcohol all behave very differently in the body and it is important not only to look at the quantity of calories we consume but also the quality! Every person is unique in their requirements but as a general rule of thumb aim for:
Good sources of protein include: cheese, milk, yoghurt, chicken, fish, seafood, lean meat and tofu.
Good sources of fat include: grass fed butter, nuts, seeds, avocado, salmon, coconut oil (in sensible amounts), olives, nut & seed oils (e.g. macadamia, sesame) and oily fish (salmon, sardines, mackarel, tuna).
Good sources of carbohydrates include: good quality grain bread, soy & linseed bread, sourdough bread, light rye, oats, wholegrain cereals, quinoa, pearl cous-cous, brown rice, basmati rice, wholemeal pasta, rice noodles, fresh fruit, legumes, milk, greek yoghurt, sweet potato, corn and carsima potatoes.
So how many should I aim for?
We suggest booking in for a total body composition scan to help find out your RMR based on your lean mass. Our dietitian can then tailor this according to your health and fitness goals, macronutrient needs and activity levels.
Below is a generalised energy target for the average individual, and will therefore need to be adjusted. These figures represent average requirements for the Australian population. Actual energy needs for individuals will vary considerably depending on activity levels, body composition, state of health, age, weight and height.
|Adults over 70 years||9,450kJ||8,300kJ|
NOTE: to convert into calories, divide kilojoules by 4.2.
National Health and Medical Research Council. 2005. Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes.
National Health and Medical Research Council. Dietary Energy. Available from: https://www.nrv.gov.au/dietary-energy