Susie Burrell

‘your food, your body, your life’

How many calories do you need?

Many of us know that we eat calories, and we know that we burn them off when we exercise yet knowing exactly how many calories we need each day can be a complicated calculation. In saying that, having some knowledge about your daily calorie requirements can be exceptionally helpful when learning how to eat to lose or even maintain our weight. So without needing to spend 24 hours in a calorimeter, here are the easiest steps to take to work out how many calories you are likely to need each day to support slow but sustainable weight loss, and what those calories should be made up of.

1. Calculate your baseline

We all have a baseline number of calories that we will approximately burn each day, known as our resting metabolic rate. 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.

2. Create a deficit

To lose ½ – 1 kg 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 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.

3. Next add in your activity

Now this is where many people seeking weight loss go wrong. They cut back on their calories but they forget that they will also need more if they are exercise. The reason for this is that 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 strange as this may sound. As a general rule of thumb we will need at least 200 extra calories per hour of physical activity that we do. That means if you go to the gym for an hour and are a small female trying to lose weight eating 1200 calories, most likely you will need more calories or 1400-1500 calories to lose weight when you are exercising.

4. Pay attention to your hunger

While we have these rough ways to calculate the number of calories we require, another powerful sign may be how hungry we are. If you are eating 1200 or 1400 calories and are hungry all the time, it is the body telling you that you actually need to eat a little more. The best time to add an extra 100-200 calories, early in the day, at either breakfast or lunch or before the time that you exercise. Experiencing a little hunger in between meals is ok, it is relentless hunger and extreme cravings that we need to pay attention to.

5. Check your macros

It is commonly thought that when you consume fewer calories than you need you will lose weight but this is not always the case. The wrong balance of our key macronutrients – protein, carbs and fats can impact our ability to burn body fat as well. For example, diets can actually be too low in carbohydrate to support fat metabolism but not low enough to induce ketosis – it is this grey area of carb intake that can often explain weight loss plateaus in individuals who are actively trying to keep their carb intake low. The average person will successful drop ½ – 1kg a week on diets that contain 30-45% carbohydrate, 30% or less of fat and 25-30% protein. You can check your macronutrients on MyFitnessPal or have a dietitian calculate them for you.

6. And….. change things around

The interesting thing about weight loss is that we do need to change things around as you lose body fat and become more efficient at burning calories. While you may initially lose weight on a 1200 calorie plan, over time you will find that you may actually need to eat an extra 200-300 calories to continue to lose weight. So if you find your weight loss has plateaued you may find that eating a little more is the key to ongoing success, especially if you are hungry, or you may also need to exercise more to build more muscle and increase your metabolic rate.