What Is A Calorie Deficit And How Big Should It Be?

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February 5, 2024 - Updated February 5, 2024

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If you’re at the start of your health and fitness journey or have been leading an active lifestyle for a while, you’ve likely heard the term “calorie deficit” thrown around - especially at the start of a new year.

We know that weight management, weight loss and even understanding caloric theory aren’t goals or priorities for everyone (nor should they be!), but if you’ve been wanting to get your head around all things calories and the role it can play, we wanted to make it easy to understand. 

We’ll start by laying some essential groundwork and explain what a calorie even is in the first place, before diving into all things calorie deficits, calculations, calorie counting, how to eat, building muscle, why you might not be losing weight, and who calorie counting is not a good approach for.

Back to basics: What is a calorie? 

Simply put, a calorie is a unit of measurement used to measure energy, in the same way you might use inches, kilometres or miles to measure space or distance. 

Every day, your body burns a certain number of calories at rest to maintain your bodily functions such as heart rate and digestion. This is known as your basal metabolic rate (BMR) or resting metabolic rate (RMR). Your body also burns calories through movement and exercise, whether you’re taking the bins out or doing a 30-minute HIIT workout. Where do these calories come from? The source your body uses can either be stored energy in the form of fat or muscle, or calories consumed through food and drink. 

What is a calorie deficit?

Your BMR is the certain number of calories your body needs each day to power basic bodily functions. If the number of calories you’re consuming each day in the form of food and drink matches the number of calories you’re burning, the energy scales are balanced and you will maintain your current weight. 

If the number of calories you’re consuming each day is less than the number of calories you’re burning, the energy balance becomes tipped and you’re in a calorie deficit. If you’re consistently in a calorie deficit, your body will draw on energy stored in your body and you’ll gradually lose weight. 

The Cleveland Clinic and Mayo Clinic summed up a calorie deficit nicely by saying that losing weight essentially comes down to the one thing - burning more calories than you’re eating. Changing the energy balance and creating a deficit can be done through eating less (calories in), moving more (calories out), or a combination of the two!

How to calculate a calorie deficit

The easiest way to calculate a calorie deficit is to use an online calculator, which will typically ask for details such as your age, height, weight, sex and activity level to determine the closest estimated number of calories your body burns each day.

Depending on how much of a calorie deficit you want to be in, you would then minus this from your daily energy requirements. For example, if your body burns 2,500 calories each day and you want to be in a 500 calorie deficit, your new daily calorie intake would be 2,000. 

It’s important to remember that any calorie calculations are always estimates and there are several factors online calculators can’t take into consideration, such as genetics, medications, stress and health conditions. 

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How much of a calorie deficit do you need to lose weight? 

Before reducing your calorie intake, it’s always recommended to consult your healthcare provider, but the Cleveland Clinic says that generally, losing about 500g or one pound per week is considered to be a healthy and gradual approach to weight loss, which translates to (roughly) a 500-calorie deficit each day. If this sounds like a significant deficit or you’re happy for your weight loss to occur at a slower rate, no problem! You can go for a smaller calorie deficit. A deficit is still a deficit, whether it’s 100 calories or 500!

On the flipside, it’s not recommended to significantly increase your calorie deficit to achieve a faster rate of weight loss. While the math equation makes sense on paper, Harvard Health caution that reducing your calorie intake too sharply can negatively impact your health by depriving you of nutrients. Not to mention, you probably won’t  be feeling your best. 

If you create a calorie deficit that is too large you’ll not only be ravenous but may also experience unwanted side effects such as nausea, constipation, headaches, fatigue and irritability. Not fun for you, and not fun for your loved ones either! A deficit of 500 calories or less is a far more healthy, gradual, enjoyable and sustainable way to lose weight. 

How to count calories

The most common and convenient way to count calories is to use calorie-counting apps, where you can enter the food and drinks you’ve consumed each day and see the tally add up in real time. This can be time consuming and take some practice getting used to, as you not only need to enter the ingredients but also the weight or size of your portion.

For many people who habitually count calories, understanding the rough calorie value of different foods and beverages often becomes second nature, without having to check an app.

If you’re trying to get a better understanding of the energy and nutritional value of different foods to improve your diet, calorie counting apps can help, even if you only use them as a short-term educational tool.  

Is calorie counting bad? 

Calorie counting in itself isn’t bad for you, it’s simply a tool that can assist with weight loss, management or understanding food and energy. By the same token, that doesn’t mean calorie counting is right for everyone. 

As the University of Sydney explains, calorie counting can do more harm than good for some people if it takes the pleasure out of food or contributes to an unhealthy relationship with food, exercise or your body in general. It also isn’t a recommended approach for those with a history of disordered eating, as research has shown it can trigger, contribute to or worsen symptoms.

If you’re currently calorie counting and it’s having a negative impact on your relationship with food or your overall wellbeing, it might be time to try a different approach or see a professional for advice. If you’ve never counted calories and are planning on giving it a try, it can help to schedule regular check-ins with yourself to reflect on how you’re feeling and whether it’s working for you.

For people who want to lose weight without counting calories, there are plenty of other strategies you may have success with, such as eating smaller portions, increasing your consumption of fruits, vegetables and protein, and cutting down on fast food, alcohol, and sugary treats. You can also visit a nutritionist or dietician for a meal plan tailored to your needs!

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How to eat in a calorie deficit

Eating less than you burn sounds simple enough if you’re trying to achieve weight loss, but what’s the best way to actually do that when it comes to your food choices? What should you eat? While there’s no one size fits all approach (just look at the nutrition section of a bookstore), it’s best to make sure your habits are sustainable, gradual while still providing your body with plenty of energy and nutrition. 

Aside from the task of calorie counting itself, here are some common, healthy strategies that can help to reduce your overall calorie intake:

  • Reduce or eliminate your consumption of alcohol which is high in calories and lacks nutritional value

  • Eat smaller portion sizes

  • Eat less fried foods, sugary drinks, takeaway foods, baked goods, or foods high in sugar or saturated fat

  • Focus on eating more fruits and vegetables which are nutrient-dense and low in calories, meaning you can eat plenty!

  • Focus on eating plenty of protein to keep you full and maintain your muscle mass. Protein also has a higher thermic effect than carbohydrates and fats, meaning it requires more energy to digest which can contribute to a higher daily calorie expenditure

  • Reduce the hours in which you eat (aka intermittent fasting), which can mean consuming less calories overall

  • Reduce snacking when you’re not hungry

  • Choosing leaner cuts of protein

  • Eat more homemade meals so you know what you’re eating 

This isn’t an exhaustive list, but some of the strategies we don’t recommend when it comes to healthy and sustainable weight loss include:

  • Cutting out food groups unless you have allergies or intolerances

  • Crash or detox diets such as juice cleanses and tea detoxes

  • Significant calorie restrictions

  • Overtraining

  • Liquid diets

  • Having meal replacement shakes instead of food 

  • Only eating a limited number of foods

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Can you build muscle in a calorie deficit?

Yes! If you’re strength training while in a calorie deficit, it is possible to build muscle, you just need to focus on two things. Firstly, make sure your deficit isn’t too significant - you still need plenty of energy to sustain your training. Secondly, focus on eating plenty of protein - the macronutrient key for building and repairing muscle (and keeping you full!). The Cleveland Clinic highlights that eating a higher protein diet over a long period of time has been linked to eating less and weighing less. 

Some people who have goals to increase muscle also use calorie counting apps, not necessarily focusing on the calories themselves but on how many grams of protein they’re eating each day to make sure they’re consuming enough for muscle recovery and growth. This is what people mean when they talk about counting macros or macronutrients!

Why am I not losing weight in a calorie deficit?

This question opens up a big can of worms and it’s hard to give a solid answer when everyone’s situation and body is different, but here are a few of the things which could be at play.

If you’ve only been in a deficit for a week or two and you’re not seeing any weight loss, give it a bit more time for your body to adjust. On the other hand, if you’ve been in a deficit for several weeks or months and you’re not seeing any weight loss (or you’re gaining weight), you’re either not in a deficit, or there’s something deeper going on, so it’s always best to see your healthcare provider for advice in this situation. 

If you’ve been in a calorie deficit for a while but it was your first time calculating your calorie requirements, the University of Sydney says it’s important to remember these calculators only provide an estimate and there are so many other factors they don’t consider. It is definitely possible the calculations of your daily energy requirements and your recommended deficit weren’t 100 percent accurate, and you may need to experiment with a slighter larger deficit.

Another situation is when you’ve been steadily losing weight and suddenly things have come to a halt. As you lose weight, your metabolism shifts and your daily energy requirements actually decrease. Basically, a smaller body requires less energy to power! If you’ve reached a healthy weight, fantastic! Otherwise, you may need to increase your deficit slightly again or redo your calorie calculations with your new weight.

The University of Sydney also points to research suggesting each of our bodies have a “set point weight”, meaning a genetically predetermined weight your body tries to maintain regardless of what you eat or how much you exercise. This can trigger increased hunger signals or slow your metabolism to try and prevent your body from losing too much weight and encourage you to fuel up more! 

Again, with any reductions to your calorie intake you plan on making, confusion about what a healthy weight is for you, or questions about why you’re not seeing change, see your healthcare provider or a dietician to make sure you’re making any adjustments in a safe and healthy way.

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And fuel yourself forward

Calorie counting isn’t good or bad - it’s just a tool. Your best friend might find calorie counting a helpful, straightforward way to understand food and weight management, while for you it might suck all the joy out of food and be a soul-destroying task. When it comes to food and fitness, it’s all about finding what works best for you.

Looking to better understand food, weight management or achieve weight loss goals? Your best place to start is always your healthcare provider who can guide you in the best direction to ensure you’re taking a gradual, healthy approach and still nourishing your body each day.

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A more empowered you starts with Sweat, and our editorial team is here to bring you the latest fitness tips, trainer recommendations, wellbeing news, nutritional advice, nourishing recipes and free workouts.

* Disclaimer: This blog post is not intended to replace the advice of a medical professional. The above information should not be used to diagnose, treat, or prevent any disease or medical condition. Please consult your doctor before making any changes to your diet, sleep methods, daily activity, or fitness routine. Sweat assumes no responsibility for any personal injury or damage sustained by any recommendations, opinions, or advice given in this article.


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