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In order to be a calorie deficit, you need to;

  1. Estimate your maintenance calories
  2. Based on that, set a daily/weekly calorie target
  3. Stick to that target consistently 
  4. Monitor weight, activity and calories consistently so you know when/if you need to reduce your calorie target to lose more weight


A calorie deficit is a state where you’re taking in fewer calories than you burn, over a given period of time.

So, if on a given day you burned 3000 calories, but only ate 2000 calories, you’d be a calorie deficit of 1000 calories. The bigger deficit you’re in, and the longer you maintain that deficit, the more weight you’ll lose.

When we say ‘burn’, we don’t just mean through ‘formal’ exercise (e.g. running/cycling), we mean your total TDEE (Total Energy Expenditure), which is made up of several factors.

These factors are;

  • Your RMR (Resting Metabolic rate) i.e. how many calories you’d burn if you just layed down all day N.B. this is also known as BMR (Basal Metabolic Rate)
  • Your Formal Exercise, i.e. how many calories you burn through formal exercise like lifting weights or running
  • NEAT (Non-Exercise Activity Thermogenesis) – how many calories you burn through stuff like walking around, fidgeting, or doing the housework
  • TEF (Thermic Effect of Food) – how many calories you burn through the digestion of food. Some food takes more calories to digest than others, for example, protein requires more effort to digest than fat

The sum of these four aspects will determine the total amount of calories you burn each day

metabolism (NEAT, BMR, etc)


If you burn more calories than you eat over a given period of time, you will lose weight.

Let’s use the above example.

If you burned 3,000 calories, but only fed your body 2,000, the energy for that other 1,000 has to come from somewhere – of course, the desire for most people will be that this 1,000 calories will come from bodyfat, and the likelihood is that most of it will, but some may come from muscle.

What does a 1,000 calorie deficit in a day actually mean for weight loss?

Well, if you were in a 1000 calorie deficit everyday, it would take 3.5 days to burn 1lb of fat (or 7.7 days to burn 1kg of fat). This is because 1lb of fat contains 3,500 calories (1kg of fat contains 7,700 calories).

If you want to lose more weight, you simply increase the size of the calorie deficit.

Let’s say you wanted to lose 10lbs (4.5kg) of body fat. That means creating a calorie deficit of 35,000.

If you wanted to do that over a 3 month period that would mean an average daily calorie deficit of 389 calories.

If you currently maintain your weight on 2,000 calories, that would mean that you need to eat an average of 1,611 calories per day for 3 months.

Simple maths.

Except we’re talking about the biochemistry of the human body, psychology and behaviour so it’s not always quite that simple…



But calories in do affect calories out – so although you might assume you’re in a deficit of 389 calories per day (using the example above), you may not be.

When you drop your calories, your activity levels will subconsciously drop – this is because your body notices a decrease in energy intake, and so will dop energy expenditure to compensate. This may be small stuff like fidgeting, stretching or walking around the house, but it all adds up over time.

Let’s take a look at an example of how energy intake can affect energy output.

We’ll use a completely made up person – this is Anne, 42 from London. Anne maintains her weight on 2000 calories, and decides to start dieting on week 4.

Average Daily Energy Intake (calories)Average Daily Energy Output (calories)Size of Deficit
Week 1200020000
Week 2200020000
Week 3200020000
Week 4 (start of diet)18002000-200
Week 518002000-200
Week 616002000-400
Week 716002000-400
Week 816001900-300
Week 916001900-300
Week 1016001800-200
Week 1116001800-200
Week 1216001700-100

In this example, you can see that Anne reduces her calorie intake to 1800 calories at the start of her diet, creating a 200 calorie deficit, in week 6, she reduces it by a further 200 calories, creating an even bigger deficit (400 calories).

But there’s a plot twist, in week 8, her average daily energy output falls by 100 calories, meaning the size of the deficit is reduced.

A deficit still exists, so weight loss will still happen, but it’s smaller than before, so the weight loss will happen a slower rate.

The graph below represent this in a more visual way – the yellow line (size of the deficit) reduces as the energy output reduces (red line) BECAUSE energy intake has been reduced (blue line).

All of this means that weight loss isn’t necessarily a linear, predictable process because there are so many moving parts.

You can do all of the calculations in the world, but your body may not respond to a certain amount of calories the way you suspect.

Does this mean that trying to calculate a calorie deficit is pointless?

Absolutely not – but it does mean that you can’t just set a target, stick to it and expect a consistent level of weight loss, you need to continually track and monitor your progress so you know when to adjust your calorie intake based on your rate of weight loss.

Anyone can do this themselves with a bit of hard work and patience, but hiring a weight loss coach will make the process a lot easier.


So now we’re armed with the knowledge of what a calorie deficit actually is and how it works, how can we go about actually creating a calorie deficit?

The first step is to calculate our maintenance calories, otherwise known as our TDEE or total daily energy expenditure.

There are many different ways to do this and while some people may claim that one is the most accurate, none of them can be 100%, so be aware whatever method you use will be an estimate.

If you want a free e-book guide for calculating maintenance calories, stick your email below and I’ll send you one.


Once you’ve got your maintenance calories (remember this is an ESTIMATE), you can then go and set a calorie target target for yourself.

This should be based on two things;

  1. How Much Weight You Want to Lose
  1. How Quickly you want to lose it

Let’s say you want to lose 10lbs (4.5kg). You then need to establish how quickly you want to lose it

As we established above, 10lbs of weight requires a 35,000 calorie deficit (in theory), so the sooner you want to lose it, the more aggressive your diet would need to be.

Let’s also assume our maintenance calories are 2000 per day.

Here’s how many calories you’d need to eat per day on average to lose 10lbs across different timeframes

TimeframeRequired Daily Calorie Intake
1 month333
2 months1417
3 months1611
4 months1708
5 months1767
6 months1806

Clearly, as the timeframe increases, the severity of the required deficit reduces.

Which timeframe should you pick? It depends how aggressive you’re prepared to go with calories, and what your willpower is like.

I certainly wouldn’t recommend that ANYONE try to lose 10lbs in a month; sticking to 333 calories everyday simply won’t be sustainable.

The more calories you give yourself, the easier it’ll be to stick to, so I’d recommend trying to strike a balance between speed and sustainability – sustainability will always trump speed however.


Well, if you can’t stick to your target calories,  you likely won’t end up losing any weight. Better to take things slow and get the result rather than rush, and give up because it’s too difficult.


There’s no right answer to this question, it really depends on the individual.

If you have a hard target for your weight loss (e.g. a wedding or holiday) then you’re kind of backed into a corner.

If there’s no hard target, you can take this a bit slower (although you should still set an end date).

How long you give yourself will depend on how hard you can diet.

If you’re a busy professional that’s always on their feet and out for lunches, dinners and drinks then an aggressive calorie deficit may simply be too difficult to stick to.

If you work from home and have a relatively consistent daily schedule, it’ll probably be a lot easier.

This ultimately comes down to you.

What I wouldn’t advise is setting an arbitrary figure. A 500 calorie deficit is a number that seems to be thrown around quite a bit and while it’s a nice round number, it won’t suit everyone.

Let’s say you’re a small female weighing 50kg and you currently eat and maintain your weight on 1500 calories per day, 500 is a huge and very noticeable chunk to cut out (33%) of your calories.On the other hand, if you’re an active 90kg male you might maintain your weight on 4000 calories per day, in which case, 500 isn’t a huge amount to take out (12.5% of daily calories).

Use the methods described above if you have a clear amount of weight you want to lose in a predetermined time frame. If not, make sure the size of your calorie deficit is proportionate to your current maintenance calories.


As you can see above, the math around creating a calorie deficit is quite simple, the difficult part is creating that calorie deficit in a sustainable way, i.e. in a way that fits into your lifestyle and you can maintain for a long time.

There are many well-known diets out there that help you create a calorie deficit and lose weight. The problem is, most of these diets are NOT sustainable.

Let’s look a couple of examples;

Weight Watchers

Weight Watchers is a dieting ‘club’ in the UK with an in-person community aspect and ‘leaders’ that will conduct weekly weigh-in sessions. This is highly motivating for many, and I personally know lots of people that have lost weight during their membership.

But what happens when you stop your membership? Weight Watchers assign ‘syn’ values to food that are essentially made up (as opposed to just focusing on calories, which are real). You don’t know how to eat in a way that maintains your weight, so you’ll most likely put it all back on.


This is a method of dieting which bans pretty much all carbs.

And guess what? It works for a lot of people.


Because carbs make up a large part of most people’s daily calories (fruit, bread, rice, pasta etc), if you get rid of them, you eliminate a lot of calories so you’ll lose weight.

But this is because of the CALORIE reduction rather than the CARB reduction. If you reduced fat or protein you’d see similar results.

So what happens when you stop doing Keto? You regain all of the weight you lost because you don’t know how to maintain your weight while eating carbs.

And let’s be realistic, NO ONE is going to stop eating carbs for the rest of their life.

So, how can you create a calorie deficit, that will help you lose and MAINTAIN your weight in a sustainable (i.e. you can do it forever) way?

Weekly rather than daily calorie targets

Having a calorie target will give you something to aim for, but daily targets can be quite restrictive – if you go over your calories one day you might feel like you’ve screwed up your diet and give up.

This is why weekly targets are much easier to stick to. Look at the two examples below, which looks more like a ‘normal’ lifestyle;

Daily Targets:


Weekly Targets:


Both examples have a total of 14,000 calories taken in throughout the week, but the person with weekly targets has much more flexibility, which allows them to up their intake on Saturday to account for a takeaway and drinks (for example).

Food Volume

Just eating ‘what you want’ while sticking to a prescribed amount of calories sounds great – and it can be as long as you ensure you’re eating a way that will make you feel full and energised enough to go about your life.

While you theoretically CAN lose weight just eating chocolate and cake and cheese, I wouldn’t recommend it.


Those foods won’t fill you up, and if you’re hungry all the time, you’re going to feel like trash.

You’re far better off prioritising low calorie dense foods – i.e. food that weighs a significant amount, but doesn’t contain a lot of calories, this means it’ll take up room in your gut and make you feel full and satisfied.

Great examples of these foods are vegetables, fruits, beans/legumes, yogurts and lean meats like chicken, turkey, certain cuts of pork and white fish. Here’s a list of some low calorie dense foods (the nearer the top of the list, the lower the calorie density).

Prioritise Protein

Protein is the most important macronutrient in your diet.

This is because it helps to maintain and/or build muscle, helps you feel fuller, has a high thermic effect (it takes more calories to digest) and it contains (depending on the source) many other beneficial micronutrients.

You should look to base each of your meals around a protein source. E.g.

Breakfast – Eggs or Yogurt

Lunch – Deli meats like sliced turkey or ham

Dinner – Chicken, Steak, Pork, Salmon, White Fish etc

Snacks – Jerky, Protein Bars, Boiled Eggs, Milk

Aim to get at least 1.5g of protein per kg of bodyweight. This means that if you weigh 80kg, you should aim for a minimum of 120g of protein per day


You’ll never be able to calculate exactly how many calories you should be eating for weight loss, but you do at least need something to aim for.

Once you have that, you can track your calories, activity and weight everyday. This will tell you if the amount of calories you’re eating is low enough to produce weight loss, or whether you need to lower it some more.

Remember to eat in a way that means you’ll feel full and satisfied, while leaving room for the odd treat here and there.

It’s simple, but not easy.

Joe is an online coach and qualified personal trainer of 15 years who helps busy, professional men and women lose weight and build muscle.

Having a 9-5 desk-job, Joe understands the struggles of juggling a hectic life with trying to maintain a good physique.

If you want to know more, check out the about page, or get in touch

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