They are listed on food labels, frequently referred to in popular diets and something we talk about without necessarily knowing what they should mean to us in terms of our daily food choices – calories.
What are calories?
The units of energy produced when food is digested, and ultimately what determines if we are gaining or losing weight.
Each and every person has different calorie requirements depending on their age, gender, activity levels and the goals they have for their body, and as such there is not a set number of calories a person requires.
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That’s why many diets are based on significant calorie reductions which ensure weight loss should the regime be followed. But there are a number of metabolic consequences that come from consuming too few calories over an extended period of time.
When it comes to calories, less is not always best. So, how can you work out how many you need, especially if the goal is sustainable weight loss?
Fewer is not the goal
The risk when it comes to calories is that we hold the belief fewer is better. What’s important to remember is that the body requires a certain number of calories each day to preserve metabolic rate.
For the average small woman, this is roughly 1000 calories. This means diets that promote extreme restriction, or calorie intakes less than 1000 a day for long periods of time, are inevitably resulting in a reduction in metabolic rate. Over time, this means muscle mass will be reduced, and weight control will actually become more challenging.
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Working out your baseline
We all have a baseline number of calories that we will approximately burn each day, known as our resting metabolic rate — the bare minimum your body needs to actually function.
There are some online applications such as ‘myfitnesspal’ that can help you calculate this based on your height, weight, age and gender, although there will always be slight inaccuracies depending on how much muscle mass each individual has. As a rough guide, a female will need a minimum of 1200-1400 calories each day, whereas a male who generally has more muscle mass will need 1400-1800 calories.
If your goal is weight loss
To lose ½ – one kilogram of body fat each week, you will need to create a calorie deficit of 200-300 calories each day. It is for this reason that weight loss diets often focus on 1200 and 1500 calories – they are roughly 200-300 calories less than the person needs to function.
You can easily cut back on calories each day by watching portion sizes, minimising mindless munching and cutting back on high calorie foods such as cakes, biscuits, chocolate and alcohol which contain at least 200-300 calories per serve.
Don’t forget to consider your exercise
Now, this is where many people seeking weight loss go wrong.
They cut back on their calories but they forget they will also need more if they are exercising. The reason for this is an active muscle burns extra calories, and if we do not eat enough calories to fuel the muscle, fat loss will slow down.
This explains why people training an hour a day and eating only 1200 calories do not always lose weight, they actually need to eat more.
As a general rule of thumb, we will need at least 200 extra calories per hour of physical activity we do. That means if you go to the gym for an hour and are a small woman eating 1200 calories, most likely you will need closer to 1400-1500 calories to lose weight when you are exercising.
Keep a eye on any extras
The funny thing about calories is that it is not our day-to-day intake that tends to derail us, rather the little extras that slip in on a daily basis – the mouthfuls of kids’ dinners, or extra chocolate at work, or the extra-large glass of wine.
For this reason, if you are not sure why you are not getting the results you are looking for with your current diet, tracking a day or two of everything you eat is an easy way to see where little extras may be slipping in and blowing out your daily calorie intake.
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Author Susie Burrell is a leading Australian dietitian and nutritionist, founder of Shape Me, co-host of The Nutrition Couch podcast and prominent media spokesperson, with regular appearances in both print and television media commenting on all areas of diet, weight loss and nutrition.