Weight Loss 101: Calories in Vs Calories out

Hi, my name is Trent, @tzonedevlin, and for the last 10 years I have been helping people just like you achieve their fitness goals, whether that be losing weight, gaining muscle, competing in sports events or even just posing on the beach.
In the next few articles I'd like to impart some knowledge that will help you move from the unfit, effort shy, gym bunny paying monthly fees to corporate fitness vampires into an all-terrain, all-weather, all-location fitness machine.

People tend to train for a multitude of reasons, but by far the most common is weight loss. There are numerous different factors to take into account when losing weight, from hormones, to stress levels, sleep patterns and obviously how many pieces of chocolate cake you have with that full fat caramel latte

But by far the most important thing to consider is:

Calories In Vs Calories Out

Now there are a number of schools of thought when it comes to this simple equation, first,

The Whole Food Fascists
You know, the ones who harp on about organic this and naturally produced that, the ones who sneer disdainfully as you rush by with that hurriedly bought pre-packaged sandwich because you're late for work and they sip on their wheatgrass and tofu smoothies, they would have you believe that everything you eat is wrong and killing you from the inside out like the cute dude from the Alien films.

Then you have the other team,

The Pot Bellied Power Lifters
These are the guys you see in every gym, troughing down protein shakes between every exercise and giving out unwanted advice, they'll convince you that you can eat what you want as long as you're training.

So which group of annoying busybodies is correct... well, both of them are... to an extent.

If you eat only junk food you're probably going to get poor results from whatever training plan you're following, the often quoted metaphor is that if you had a Ferrari would you fill it with anything less than premium fuel?
To use the same metaphor for the other argument, we could say that even less than premium fuel will be burnt up if the Ferrari is driven enough.

The problem that both of these points of view have is that they don't really focus on the equation itself. The equation is simple and rather than being based in nutrition and biology it is based in the laws of thermodynamics. It takes a certain amount of energy to move a certain amount of mass a certain distance in a certain time. Simple huh?

So how does this relate to us and our quest lo lose weight? Well, calories are simply a unit of energy. We store this energy in the cells of our body, we then use this energy when we move around and go about our general body functions. To replace this energy in our cells we consume calories which then get stored in our body cells and the whole cycle continues.
So to lose weight what we need to do is burn more calories than we consume, this way the calories that are taken from cell storage aren't replaced. This is called:

Calorie Deficit

How do we work out calorie deficit? Well there are two parts, we need to work out how many calories we take in.
This is the fairly simple part of the equation, if you don't want to be checking the calories on the side of every food packet and don't have a calorie chart to check everything as you eat it, you can always keep a food diary.

Once we know how many calories we take in we need to focus on calories out, that is the amount of calories we burn.
Here is where things get a little bit more complicated, the calories we burn are made up of two distinct parts, our resting metabolic rate and the amount of work we do. Unless you have access to some pretty extensive lab equipment working out you resting metabolic rate is going to be more of an estimate, but using a few formulae we can get pretty close.

I tend to use the Mifflin St. Jeor Equation (mainly because it has the coolest name, and it's been proven to be 5% more accurate than the previous one):

P = (10M)+(6.25H)-(5xA)+S

Where 'P' is Calories burned per day, 'M' is weight in kilos,'H' is height in centimetres, 'A' is age and 'S' is +5 for gents and −161 for ladies.

So using this formula, Melissa, a 5ft 3, 35 year old woman who weighs 53 kilos would have an RMR of 1160.
That means just by sitting and existing she would burn 48 calories per hour.

Now I could also write out a formula for working out how many calories different activities will burn and another formula using that figure to work out how much each individual would burn doing each activity for however many minutes, but generally one formula per post is pretty much all most people can handle before zoning out.
Instead let's keep it simple... ish

Take your RMR and use a multiplier based on how active your lifestyle is:

Multiply by 1.1 for a sedentary lifestyle (little or no exercise)
Multiply by 1.3 for a lightly active lifestyle (moderate exercise 1-2 times per week)
Multiply by 1.4 for a moderately active lifestyle (moderate exercise 3-5 times per week)
Multiply by 1.6 for a very active lifestyle (hard exercise 3-5 times per week)
Multiply by 1.9 for an extremely active lifestyle (hard exercise more than 5 times per week)
Multiply by 2.1 for athletes!

So let's apply these multiplier's to Melissa who has a moderately active lifestyle, she works out 3-5 times per week.
Melissa's calories out side of the equation would amount to approximately 1624 so to put herself into a state of calorie deficit she would need to consume less than this amount daily to start to lose weight.

So that's it really, weight loss is down to calories in Vs calories out, everything else fits under one side of the equation or the other.

But let me finish with a few words of warning, obviously the larger the deficit the faster the weight loss, but aiming for a calorie deficit of more than 30% of RMR a day could cause other health related issues and undue stress on the body's other organs. If you want to lose weight, do it safely.

If you would like me to post any specific fitness related content or just want to say hi, please comment below