The Weight Loss Equation

image source: Microsoft clip art
Image source: Microsoft clipart
The 'secret' to my weight loss was basically an equation.  Based on a target loss of 1lb a week, I calculated my net calories for the day (which can be defined as: Calories consumed (food) - Calories burned (exercise) = net calories) and stuck with them. This method may seem counter-productive at first, because it means eating back the calories you've just burned off (which is why my motto is 'burn it to earn it'). It works because in the calculation of you own personal net calories for the day, a deficit of 500 calories has already been made. 

A deficit of 500 calories a day is necessary for a steady, health weight loss of 1lb a week. The way the formula below works: it provides you with the amount of calories you'd need to eat to lose weight before exercise - in other words,  the 500 calorie deficit would be coming from food alone. To make it easier, as well as gain the other health benefits from exercising, my advice is that you then workout to 'earn' more calories to eat but stay within your net calorie goal. This way a deficit has been created from both food and exercise. 

This may sound confusing for now so allow me to demonstrate how to calculate your net calories and then illustrate how it works using an example. I will also explain at the end how to track your calorie consumption and expenditure so that you can but the numbers into action an start losing weight. 

Calculating your allotted daily net calories in three steps:    

1. Firstly, we need to calculate your BMR (Basil Metabolic Rate). This is often described as the number of calories we would burn if we were to lay in bed all day. In other words, what our body burns just to operate your organs and handle the various processes that take place internally.

To to this you'll need to accurately know your weight in KG and height in CM. 

If you need to, you can use google's built in conversion to convert your weight from lb to KG. Simply type in [Your Weight]lbs in kg, for example typing "148lbs in kg" into google brings back "148 pounds = 67.1316708 kilograms" so we would round this to 67kg. 

Now pop these details into the appropriate Mifflin-St.Jeor equation below: 

Male: BMR = (10 × weight) + (6.25 × height) - (5 × age) + 5

Female: BMR = (10 × weight) + (6.25 × height) - (5 × age) - 161

Once you've done this, you have your BMR. Now we need to add on the calories for your daily activity, NOT including any additional exercise. So base this on your job/occupation rather than any workouts.

2. Calculating your daily activity (excluding workouts)  
  • Sedentary: Spend most of the day sitting (e.g. desk job):  BMR x 1.200
  • Lightly Active: Spend a good part of the day on your feet (e.g. nurse, sales assistant) : BMR x 1.357
  • Active: Spend a good part of the day doing some physical activity (e.g. waitress, mailman): BMR x 1.550
  • Very Active: Spend most of the day doing heavy physical activity (e.g. construction worker): BMR x 1.725
If, like me, you're not really sure which category you fit into (whether you're unemployed, or your days vary too much, or maybe you work on a casual basis) then I advise you go with sedentary Then when you are being active without working out, for example, walking to the shops, count these calories using a pedometer or a HRM and add these in the same way as you would exercise. (Which we'll come to in a minute.)

Ok, so by now you'll have a number that takes into account your BMR an daily activity. Still with us? Great. Now for a very simple step 3:

3. Creating a deficit

For 1lb a week weight loss, (which I recommend as it's healthier and far easier to manage long term than overly ambitious 3lb + a week) subtract 500 from the number you have in front of you. For 1/2lb a week subtract 250 calories (ideal if you're on the last 5 lbs of your goal or if you only have a little to lose in the first place). 

An example:
Now I'll show you an example of the whole calculation so you can check you're on the right track:

Say we have a 21 year old woman who is 196lbs and 5ft 2 making her obese, so she needs to lose 1lb a week to eventually reach a healthy BMI of 22.

First, we'll convert her stats so that they fit into the Mifflin-St.Jeor BMR equation:

That's 89kg and 157cm.

Female: BMR = (10 × weight) + (6.25 × height) - (5 × age) - 161


BMR = (10 × 89) + (6.25 × 157) - (5 × 21) - 161

which then becomes: BMR = 890+ 981.25 - 105 - 161

The answer to which is: 1605.25 which we'll round to 1605

So this woman's BMR is 1,605. Now, we'll add her daily activity (not including exercise) as sedentary. So that's BMR x 1.200.

1605 x 1.200 = 1926

So if this woman wanted to maintain her weight, she would eat 1,926 calories a day, plus anything extra that she burns through workouts or walking to the shops. This woman however, wants to lose 1lb a week to get fit and healthy, so we make a deficit of 500 calories. 

1926 - 500 = 1426

So to lose 1lb a week, this woman will need to eat a net of 1,426 calories a day. 

Notice we said a net, that means, she can eat 1,426 calories, go for a walk, burn off say, 250 calories, eat 250 calories back, and still net at 1,426 calories. 

This little part of it seems to spark a lot of controversy, even among the community sections of the site that pioneers this method, My Fitness Pal. Many can't figure out why it's advised to eat your exercise calories back and you can find endless back and forth debates within My Fitness Pal's forums. The general consensus of many of the members and the site itself however, is that this method ensure your body had plenty of fuel to carry out it's daily tasks, and additional  fuel is provided on the days you work out. A deficit has already been accounted for when calculating your allotted net calories and it is this that results in weight loss.   

Another very important point to note here is that it is strongly advised that you do not eat less than 1,200 calories a day. If your equation comes out to a figure less than this when the deficit is put in, then use a smaller deficit (i.e. 250 calories instead of 500). It's argued that this is to prevent your body going into 'starvation mode', another heavily debated over issue which you can google and find lots of 'for' and 'against' evidence for. My argument for this is that if you're eating less than 1,200 calories a day, you are very unlikely to be obtaining the nutrition that you require. 

Tracking your calories 
So, debates and equations aside, how do you go about tracking your calories? Well, you could use a simple notebook and pen. Find out the calories you're consuming from packets, restaurant nutrition guides (often available on their websites) and books that have the nutritional information of fresh foods (for example, this book has these tables in it's appendix). You can then add on your exercise calories tracked using gadgets like pedometers and heart rate monitors, or again use books that have tables that provide rough estimates of calories burns per hour of activity. To work out your net calories for a particular day, simply add up the total amount of calories consumed (food) an subtract the total amount of calories burned (exercise). 

The simpler and much quicker way to carry out this task is to use a website like My Fitness Pal (ideal, as it uses the above equations and even calculates them for you! Among other handy features). This particular website also has apps that you can download for your iPhone, BlackBerry, Windows or Android phone which are synchronised with the website version. This means you can count calories on the go and log your workouts in the gym locker room!

TIP: Make sure you re-calculate your daily net calorie allowance for every 5-7lb lost. 

Disclaimer: Any calorie restriction equation (yes, there are others) is designed to be a guide only. Most of the time they are pretty accurate and work for many people, but there are always exceptions to any rule e.g. pregnancy, breastfeeding, athletes, etc. I am not a qualified doctor and therefore I strongly recommend that you seek the advice of your doctor before starting any weight loss plan. My advice in this post, or any other post on this blog should be treated as a suggestion, based on my own personal experience of what works and not from medical training. 

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