How many calories do you need to lose weight?

30-Nov 2013, by Lee Sandwith

how-many-calories-to-lose-weightIf you’re trying to lose weight, the most fundamental thing to understand about your body is how many calories it needs. This article explains in simple language exactly what you need to know and, more importantly, how to calculate your target calorie intake for weight loss and weight maintenance.

What is a calorie?

To start off, it’s worth reminding ourselves what a calorie is. Expressed as either ‘Cal’ or ‘kcal’ (large calorie or kilo calorie), a calorie is essentially a unit of energy. In the context of food, therefore, the calorie is a measure of how much energy foods contain per unit, commonly called food energy. The most common measure used today is the kilocalorie, or kcal, which is provided on the nutritional information found on most food packaging.

Where does food energy come from?

When it comes to food and nutrition, calorie content comes from different sources, namely macronutrients and micronutrients. Our main concern when it comes to nutrition for weight loss is mainly macronutrients: protein, carbohydrates and fat and in terms of the relative amount of energy, 1g of fat is equal to about 8 kcal compared protein & carbohydrates which are equal to about 4 kcal.

Energy Balance

Everyone knows that if you consume lots of calories then you’re likely to put weight on and if you consume fewer calories you’ll lose weight. However, it’s not a ‘one size fits all’ type of thing as everyone is different: different heights, ages, different exercise levels, body fat percentage, different metabolic rates etc.  As such, everyone has their own personal threshold that determines at which point their calorie consumption exceeds the body’s needs and, therefore, at what point they start to gain or lose weight.

Base Metabolic Rate

The important factor in all of this is called ‘Base Metabolic Rate’, or BMR for short. BMR is the number of calories your body burns in a steady state, i.e. without factoring in any additional calories burned through exercise, strenuous work and through the process of food digestion (the thermic effect of food). By factoring in these other activities you can calculate your daily calorie burn which is essentially your BMR + calories burned through exercise and food digestion. Simply put, if you consume more calories than your calorie burn you gain weight, if you eat less calories than your calorie burn you lose weight. It’s that simple! There are many other factors at play, however, this basic principle is the most important factor to consider as it helps you to calculate your daily target calorie intake. If you get this right you can easily lose weight fast and maintain your ideal weight for the rest of your life.

How to Calculate Your BMR

There are several methods for calculating BMR and, as with lots of things related to weight loss, it’s a bit of a mine-field. Essentially, there are two different approaches, depending on whether or not you have a body fat percentage reading, and several different formulas beyond that. There will inevitably be variation across all methods making it difficult to work out which is most accurate but my preference is the Mifflin St Jeor Equation which does not require a body fat reading. If you want to research some other methods you can read up on the Katch-McArdle (KA) formula or the Harris Benedict Method. If you want to do this manually you can check out the equations found through the above links but if you want to save time you can use our free weight loss calculator.

Calorie Burn

Calorie burn is simple to calculate as it is simply your BMR + exercise, however, as with BMR, there is more than one way to do it and it can be a bit of a headache. In my opinion, the best way to calculate your calorie burn is to use an activity multiplier with the below being the most accepted formula as used in the popular Mifflin St Jeor, Harris Benedict and KA BMR calculation methods:


How to Use This Information to Lose Weight

To apply this to weight loss, if you’re looking to maintain your current weight then your daily target calorie intake should be close to your daily calorie burn. If you’re looking to lose weight then you should aim to consume less calories than you burn, and if you’re looking to gain weight you should aim to consume more calories than your calorie burn. Simple! For weight loss, my recommendation is to aim for a 20-30% calorie deficit as it’s not too uncomfortable and you should see weight coming off at a steady pace. Use our free weight loss calculator to establish your daily target calorie intake.

Arguments Against the Calorie In/Out Method

Interestingly, there seems to be lots of counter views as to whether the calorie in/out model works and lots of websites have posted convincing arguments against this theory such as Healthy Enough and Authority Nutrition. Famously, the legendary Tim Ferris also puts forward a compelling argument against calories in/out in his book The 4-Hour Body.

In my opinion it’s important to consider every possible angle but bold statements which completely reject the calories in/out model are extremely unhelpful to the average person looking to lose weight.  It is completely undeniable that the best way to lose weight is to eat less and exercise more and this has been proved time and time again by thousands of people the world over and ratified by hundreds of studies into the subject.

If you need to see firm, scientific evidence in favour of calories in/out just spend a few minutes on the Harvard Gazette website and browse the plethora of articles on the subject. I agree that there are complexities within this model but fundamentally the most valuable advice available to anyone looking to lose weight is to get a better understanding of your body’s calorie needs and the calories in the food and drink you typically consume.

Are All Calories Equal?

When it comes to weight loss, calorie management is king, which means you can pretty much eat anything you want as long as you consume less calories than you burn. However, eating the right foods can help your body to burn fat much more efficiently due to the thermic effect of food. As such, what you put into your body matters, not only for weight management but for overall health and wellbeing so while it is possible to eat anything you want and still lose weight, the best way to maintain a healthy, strong body is to choose healthy foods. 

Further Reading

For more information you could check out our weight loss eBook which covers these topics in more detail. The book provides you with all of the information you need to start losing weight along with a bunch of healthy meal plans and a well balanced exercise guide. You can also use our free online weight loss calculator to find out how many calories your body needs for weight loss and weight maintenance.

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