The Short Answer: You can set a caloric deficit for weight loss by using the following formula:
66 + ( 6.2 × weight in pounds ) + ( 12.7 × height in inches ) – ( 6.76 × age in years )
655.1 + ( 4.35 × weight in pounds ) + ( 4.7 × height in inches ) - ( 4.7 × age in years )
There's simply no greater truth when it comes to diet than this one simple fact. If you are using more energy than you are taking in from your food, you will lose weight.
You're probably thinking, that’s a pretty simple way of looking at things, and to be fair you would have a point. After all, the human body is amazingly responsive and when you factor in just a few of the following considerations:
- Food preparation - How you prepare and cook your food
- The thermic effects of food - The energy your body utilizes to consume, digest, absorb and store your food
- Nutrient absorption - The total nutrients your body absorbs from the food you eat
- Changes to metabolic rate - The chemical processes happening all the time in your body and the speed at which they occur
- Exercise Activity - The energy you expend during deliberate exercise
- Non-exercise activity thermogenesis (NEAT) - The Calories you use during non-deliberate exercise activities e.g. fidgeting, walking to the kitchen.
Not to mention external factors such as food labels being out on total calories by up to 20% while still being considered compliant. Based on all of this, it’s fair to say a Calorie isn’t necessarily a Calorie.
But let's get real for a second.
The practicalities of losing weight
For most of us, it just isn’t practical to factor in that many different variables and hopes to remain even moderately sane when dieting. The truth is that all things being equal, it is virtually impossible not to lose weight while in a caloric deficit. So while there are some important considerations, there isn’t any significant advantage to be had in over complicating things.
That’s not to say setting and following a caloric deficit is a simple business. Like anything related to the human body and nutrition, there are right and very wrong ways to go about it and based on your approach the outcomes can vary pretty wildly, as can the overall impact on your health.
We’ll dive into all of this in the following, but first, let’s break down the accepted meaning of a caloric deficit. We'll then take a look at the math behind it and some of the ways your body will process a change in caloric intake.
Caloric Deficit Meaning
To accurately explain what a caloric deficit is (and how to go about calculating one for yourself) it’s important to get familiar with the concept of Homeostasis.
Homeostasis: The body’s tendency to maintain equilibrium through physiological processes.
You can consider Homeostasis simply as energy balance - the balance between the energy taken in from the food you consume and the energy being used by the body.
Remember a Calorie is a unit of energy, and if you consume more energy than your body burns up, you will find yourself in a positive energy balance or caloric surplus. When you are in a caloric surplus, you are going to gain weight. It doesn't matter if the foods you are consuming are reasonably healthy or consist of scoffing triple deep-fried chocolate chip ice-cream when it comes purely to the weight you gain.
The reason junk food is the biggest culprit here is that it's more calorically dense than most whole foods, meaning you eat a lot less for the same high number of Calories. Even worse, in most cases, this kind of food isn't as filling, meaning your appetite won't be under control for long.
On the other hand, if you are burning up more Calories than you are taking in through your food than you will find yourself in a negative energy balance or caloric deficit. If that's the case, you can bank on the fact that you will be losing weight.
To calculate a deliberate caloric deficit, we need to perform some basic math.
Specifically, we need to know our total maintenance Calories i.e. the number of Calories we require each day to continue to function and maintain our current weight, not including deliberate exercise. We do this by taking into consideration our gender, age and of course starting weight.
Basal Metabolic Rate
This figure is known as your Basal Metabolic Rate or BMR, which is simply a measure of the Calories your body burns at rest.
The formula most often used to calculate this total is known as the Harris-Benedict equation which is as follows:
BMR = 66 + ( 6.2 × weight in pounds ) + ( 12.7 × height in inches ) – ( 6.76 × age in years )
BMR = 655.1 + ( 4.35 × weight in pounds ) + ( 4.7 × height in inches ) - ( 4.7 × age in years )
BMR = 655.1 + ( 9.563 × weight in kg ) + ( 1.850 × height in cm ) – ( 4.676 × age in years )
BMR = 655.1 + ( 4.35 × weight in pounds ) + ( 4.7 × height in inches ) - ( 4.7 × age in years )
Once we have an established BMR, it’s simply a case of increasing this total amount to factor in your current activity levels (energy used during deliberate exercise). I’ve listed these below.
(No exercise) - multiply your total BMR by 1.2%
(Light exercise 1 - 3 times per week) - increase your total BMR by 1.375
(Moderate exercise 3 - 5 times per week) - increase your total BMR by 1.55
(Heavy exercise 6 - 7 days a week) - increase your total BMR by 1.725
(Very heavy exercise 6 - 7 days per week) - multiply your total BMR by 1.9
Once you have factored in your activity levels the next step is to reduce this total by your chosen caloric deficit.
How Large a Calorie Deficit is Required to Lose Weight
The truth is everybody is different. Some of us respond differently to different approaches to weight loss, such as higher or lower caloric deficits, but for almost all of us, the goal of losing weight is very much achievable.
In some cases, it may also take time for your body to adjust before it starts to respond, especially if you have been yo-yo dieting and haven’t been consistent in a nutritional sense.
What this all boils down to is the fact that you are going to need to be your own test case study to some extent. Be patient, monitor your results, get a feel for what is working for you and adjust accordingly.
In any case, when considering the ideal caloric deficit for you, consider your goals first and foremost (what exactly are you trying to achieve) and then take an honest look at where you are starting from (are you already in reasonable shape or do you have a lot of weight to lose?).
Taking it to extremes? Maybe not such a good idea
Regardless of your goals and current condition, you should never push things too far.
Extreme approaches to dieting can be at best detrimental, and worse case can be dangerous. For instance, an extreme caloric deficit can wreak havoc on your metabolic rate and hormone levels, which can affect your general mood, concentration levels, your training, sex drive and a range of other functions.
There’s also the fact that most of us want to retain as much muscle as possible and focus predominantly on burning fat. I’ve written about burning fat and retaining muscle in depth here, so I we won’t go into detail, suffice to say Catabolism (when the body consumes muscle tissue as an energy source) isn’t as large a problem as some gym bros like to think. It's also a good idea to measure your fat loss in comparison to your overall weight loss. A good set of scales that measure body fat levels is the easiest way to keep track of things yourself without requiring professional assistance.
Muscle is the most metabolically active tissue in the human body, so it makes sense that the more you have on your body, the more efficient your body will be at burning fat. So it’s something you are going to want to retain as much as possible while being in a negative energy balance. It's just a whole lot smarter to incorporate a moderate (sensible) deficit if you want to retain muscle and mostly burn fat.
Remember, if you take things slowly and plan to lose weight gradually you will keep more muscle than you would if incorporating a larger caloric deficit.
The Ideal Caloric Deficit for Weight Loss
So what is the ideal starting caloric deficit?
It’s best when considering your deficit to calculate it as a percentage. For most of us, a good starting point would be somewhere between a 10% and 20% reduction in Calories.
Why a percentage?
A percentage based approach is the most practical because it takes into account different weight ranges e.g. the more overweight a person is, the more body fat they have to lose and the less likely their bodies will consume muscle tissue while in a caloric deficit.
Just providing a number e.g. 400 Calories might be useful if you are around 195 pounds but if you are much heavier, a larger deficit is advised, or your progress will be slow.
Alternatively, if you are quite lean, to begin with, you are going to want to start with a lower caloric deficit to preserve lean muscle mass.
Let's consider the following typical example.
Say you are an average size male (as per our example above) e.g. 195lbs and in reasonable health. A good starting point for this subject would be anywhere from a 200 to 500 Calorie deficit per day. For women (approx. 166lbs) this number would be slightly less e.g. approx. 200 - 300 calories per day.
Give yourself every chance of success
When you are calculating your ideal deficit, don’t just take into account results, give strong consideration to how sustainable this many Calories per day will be for you. You can always make adjustments as you go along so try to give yourself a realistic starting point to achieve success. Regardless of how committed you are, most of us cannot stick to a diet that is too limiting.
If you have been following along you should now have a pretty good handle on BMR, activity levels and what makes for an effective deficit.
Simple enough right?
For the most part, it is, but we do need to keep in mind one critical factor. Metabolism.
Metabolic Rate and Weight Loss While In Caloric Deficit
So what is Metabolism and how does it play a role?
Metabolism is more or less a fancy term to describe the chemical processes happening in the human body, keeping us alive. Our Metabolic rate is a measurement of the rate at which Metabolism occurs and is being controlled by a range of factors including but not limited to:
- Dietary intake
- Fat to muscle ratio
- Amount of exercise you deliberately undertake
- Non-exercise activity
- Hormone function.
Your metabolic rate will have a say in your weight loss efforts. When dieting, dietary intake is altered (see above) along with your fat to muscle ratio and hormone function. For most of us, attempting to lose weight is also a two-pronged approach that incorporates exercise which, as you might expect, also has an impact on metabolism.
What this means is your body will continuously be making adjustments due to the changes in your body as a result of your efforts to lose weight. For instance, if you are in extreme caloric surplus did you know your body will speed up your metabolism (all chemical reactions occurring in the body) and utilize/burn more Calories?
Alternatively, if you are in an extreme deficit, your metabolism will slow down and preserve energy, making results from dieting inconsistent and confusing.
Remember that concept we discussed earlier? Homeostasis. Well, your body is constantly trying to reach it, and that can sometimes work directly against you.
Don’t worry, while our bodies can be stubborn there are a few tricks that can help (more on this soon). Put simply, if you maintain a caloric deficit you will lose weight. Your body can’t fight the law of Thermodynamics (energy can neither be created or destroyed) it just delays things for a little while sometimes.
Macronutrient and Micronutrient Ratio while in Caloric Deficit
You may be surprised to learn that if you maintain a caloric deficit even if consuming junk food every day you will still lose weight. That’s right; it's well documented.
The fact is if you are undertaking a caloric deficit while consuming calorically dense foods with no nutritional value you will still end up leaner than you were previously but you can bet your health will suffer. That doesn't sound like a good plan to me.
To ensure our health is prioritized it’s important to consider your Macronutrient and Micronutrient intake.
It isn’t, we are simply talking about the amount of Protein, Fat, Carbohydrates and Vitamins and Minerals you should be consuming per day as part of your allocated daily Calorie allowance. Your body relies on specific nutrients to keep performing the functions we require of it e.g. to keep producing enzymes that facilitate chemical responses in the body.
As a result, it’s important when undertaking a diet of any kind that you are wary of deficiencies occurring as this may also begin to work against your best efforts to lose weight. When it comes to the Macronutrients (Protein, Fat, and Carbohydrates), there are specific guidelines based on body type that I have addressed below.
Micronutrients, on the other hand, are a little more complicated. To keep things simple I recommend taking a vitamin supplement and ensuring you maintain a balanced diet while in a caloric deficit. Ensure you are getting plenty of servings of vegetables. (5 - 6 serves per day is recommended).
Lastly, for many of us when dieting our intake of fiber can also become a problem. If you find this is the case, be sure to add a fiber supplement to your daily intake.
Body Type Considerations
While not an exact science, we can break most people down into three specific body types:
- Ectomorph: Naturally thin
- Endomorph: Naturally athletic
- Mesomorph: Naturally thick set.
Depending on your body type and your individual goals (in this case weight loss) you would be well advised to adjust your macronutrient ratios to suit your particular body type.
Each of the body types listed above have different macronutrient requirements and in general, will tolerate Carbohydrates differently.
When it comes to your Macros, it helps to think of Protein as the building blocks of your body and Fats and Carbohydrates predominantly as fuel sources. Fats are also critical when it comes to maintaining hormone levels. Based on this; fat consumption should never dip below 15 - 20% of your total Calories.
While there's a whole lot more we could talk about when it comes to Macronutrient ratios and different approaches to diet e.g. low carb, we’re talking about improving the body’s efficiency for weight loss, and creating a fat burning environment.
The ratios below are guidelines for each of the three body types:
Ectomorphic: Naturally Thin
Mesomorphic: Naturally Athletic
Endomorphic: Naturally Thickset
As you can see from the varying ratios above, Carbohydrate tolerance is the primary variable here. A lot of people still mistakenly believe dietary fat is most responsible for body fat, but this isn’t the case.
To put it in simple terms, our bodies draw energy from our blood sugar, otherwise known as Glucose. Glucose comes from Carbohydrates which as mentioned above are an energy source. (Fat can also be manipulated as an energy source if on a low carb diet for instance, but that’s a whole other story.)
Depending on your body type, you will have different tolerances when it comes to Carbohydrates. For the naturally thickset (Endomorphic) increased Carbohydrates will result in more body fat, as any glucose we do not use as an energy source can be converted to stored energy (body fat) thanks to the hormone Insulin. Ectomorphs, on the other hand, tend to tolerate higher amounts of Carbohydrate in their diet with less body fat gained.
By now you may have realized we are going to need to count Calories to ensure we stick with the caloric deficit we have outlined.
It’s true; you are going to need to, at least initially. However, once you have a feel for what you can eat and keep within close range of your allocated daily Calories you won’t need to count them religiously every day. Experienced health and fitness professionals will often go on instinct.
There’s no harm in keeping a close eye on the numbers though and besides as you lose weight you will have to adjust your results which in turn will require you to adjust your allocated daily Calories.
What if you get stuck in a rut?
It’s not uncommon for weight loss to slow down or even stop altogether for periods of time even if maintaining a caloric deficit.
There are a few reasons for this. Firstly, when beginning a new diet most of the weight you will lose initially is what's known as water weight. Losing a high amount of water weight is particularly likely if you undertake a low carb diet, as water more or less binds to Carbohydrates. Reducing your Carbohydrate intake will reduce the amount of water your body retains.
Those who had attempted to diet before and lasted at least a few weeks will be very familiar with losing water weight. You can’t compare the amount of weight you lose in the first fortnight with the amount you may be losing after two months. Secondly, we have to consider our metabolism and the fact that it will slow as a reaction to a lower caloric intake. One way around this is to include a cheat meal.
A cheat meal is exactly what the name implies. I recommend enjoying a cheat meal e.g. take away food every 2-3 weeks. The reasons for doing so are relatively straightforward; we are essentially tricking our body into increasing our metabolic rate.
Doing this can help you break out of a rut. Don’t go overboard, however, stick to just the one cheat meal every 2-3 weeks. Don’t let things devolve into a cheat day or even worse a cheat week.
Summing Up Caloric Deficit
As I outlined at the beginning of this article, a caloric deficit for weight loss is critical if you want to achieve weight loss success. It’s easy to get lost in the details of dieting and the myriad of different approaches, but when we break things down we can reduce some of the mystery that is often associated with successful weight loss by just understanding this one simple fact. If you are burning up more energy than you are consuming from your food, you will lose weight.
I hope the information above helps you achieve your weight loss goals. If you have a question or would like to share your experiences, please be sure to leave a comment below and join the conversation.