When it comes to getting to grips with how your body stores food as fat, the analogy of your body as a fridge and freezer has got to be one of the easiest to understand.
I’m not sure where I first came across this analogy, (I think it may have been by Dr Jason Fung)  but wherever I first heard it, it stuck. It stuck because it is easy to remember and it makes understanding how our eating habits can cause us to gain or burn fat very simple. In this article, we are going to look at Fat Storage and we are going to look at it though the analogy of a fridge and freezer…(cool).
The body’s cold storage
The human body has only 3 places it can store excess calories, in the liver, in the muscle tissue and in the adipose tissue (fat). In the liver and muscles these excess calories are stored as glycogen (a type of storage sugar) and in the adipose tissue they are stored as fat. Glycogen stored in your liver is easily accessible and its job is to keep your blood sugar levels balanced between meals. Glycogen stored in your muscle is locked away, ready for when the muscle is called into action and once locked away it is kept there until used. Calories stored as fat are there for when sugar supplies run low and your glycogen stores are under pressure to balance your blood sugar levels by themselves.
In many respects the liver and muscles can be seen as a small, under the counter, fridge. Food goes in easily and when we are hungry it comes out easily again too, (from the liver anyway). One problem your “under the counter fridge,” does hove however is its size; it’s not very big but as long as you keep topping it up it will continue to supply you will all the fuel you will need and if you buy too much food not to worry because the excess can just be stored in your body’s chest freezer, (your fat cells).
Fat is your chest freezer. Food is put there for long term storage and as long as there are adequate stores of food in the fridge, food that goes into the freezer stays in the freezer. Your chest freezer is also a lot bigger than your fridge and if you do happen to fill it all the way to the top that’s not a problem either, because while you can only every own one fridge you can have as many freezers as you like.
The fridge vs. the freezer
As I have already said, your natural freezer is already bigger than your fridge… a lot bigger. So, before
you start adding more and more freezer space to your body let’s first have a quick look at just how big
difference there is.
For this thought experiment, we are going to compare the fully loaded fridge and freezer of a 6-foot-tall 80kg man with 10% body fat. (That’s lean enough to see a full six-pack of abs). Here’s a picture to give you a better idea and let’s call him Bob.
To test Bobs Fridge and Freezer capacity’s we are going to send him on a bit of walk. First, he is going to walk off all the stored glycogen in his body and then he is going to walk off all the stored fat. We are going to then compare how far bob can walk on either fuel.
So, with Bobs, liver and muscles fully loaded with all the cabs he can shove in there he will have about 400 to 500 grams of glycogen fuel at his disposal. Let’s give Bob the benefit of the doubt and call it 500 grams. So, given that there are 4 calories in every 1 gram of carbs Bob has 2000 calories of glycogen to walk off.
Assuming it takes 100 kcal to walk about 2 km, then using only his fridge for fuel Bob can walk about 40 km. before he runs out.
Now let’s look at how far Bob can get on his freezer food. At 10% body fat and at 80 kg, Bob has about 8 kg of stored body fat in his freezer. 8 kg of fat is 8000 grams of fat and given that fat has 9 kcals per gram of fat that gives Bob a staggering 72,000 calories of stored fuel.
So, assuming it still takes 100 kcal to walk 2 km, then using only his freezer fuel, bob can walk 1,440 km. before he runs out of fuel.
So what this tells us is that with our fridge able to hold about 2000 kcals of fuel and just 1 freezer able to hold 72,000, topping up our fridge all day long when we are trying to reduce the size of our freezer is probably not the best way to go.
To burn Fat don’t fill the fridge.
As you can see from the analogy above, humans have lots and lots of room in their freezers to keep them going for long periods of time and only very little room in their fridges. The reason for this is that for millions of years, humans and their ancestors didn’t have a whole lot of access to sugars. Sugary fruits and most starchy vegetables generally only grow in the summer months so to make the best use of these short-lived bonus calories the human body evolved to get as many of them as possible off the trees and bushes and out of the soil and into long our term storage as fat on our bodies as fast as possible so that when food was scarce in the winter we could survive. This can only be done by having a small fridge and a large Freezer.
In fact, the main reason most of us find sugary foods so delicious and so hard to resist is that as soon as our body detects them in our system it assumes it must be summer and therefore time to start storing fat for winter, triggering cravings to eat more and more of them.
Remember, once your fridge is full there is no other place for extra sugars (carbs) to go other than into long term storage in your freezer (fat cells). So, the trick to burning fat is to keep your fridge at least a little bit empty, that way food stored in your freezer can be utilised to make up the difference and not the other way around. Since carbs are the fuel that fill our fridge, limiting or at least controlling them is the key to reducing our fat storage, or the fuel in our freezers.
The exception to the rule
Just before you go let me add one more image of information to our fridge and freezer analogy. We all know at least one person who seems to able to eat just about anything and not gain weight. So why do they not start filling their freezer every time their fridge is full? The reasons some people can eat just about anything without putting on weight are many and complex, one example being the amount of un-coupling protein they have in each of their mitochondria and their mitochondria’s ability to use them, but to keep things easy to remember and even easier to understand, think of it like this.
People who have difficulty gaining weight don’t put all their food in either the fridge or the freezer…. They throw a lot of it in the bin. In other words, their bodies never store it in the first place. Once their fridges are full their bodies just burn off the excess as heat.
If you are having difficulty losing weight this might seem a bit unfair but then biology has never been about being fair it’s about survival and the good thing to know is that by fixing your body and slowly gaining control of your weight your body will start to use the bin a bit too… it just needs to learn how and that starts by not constantly filling the fridge in the first place. It is also worth remember that the ability to gain weight is the only reason any of us are here at all. If we all kept throwing our extra food in the bin instead of the freezer, then as a species we never would have survived the last ice age.
Oh, and one more thing to remember… just because someone is not storing excess fat does not mean their diet is not doing them a lot of damage. Weight gain is only one symptom of an out of kilter diet, heart disease, Alzheimer’s, diabetes, heart disease, high blood pressure and stroke are a few more of the symptoms and none of them are mutually exclusive. At least if you gain weight when you eat badly you can tell there is something wrong but if your damaging diet is being hidden from you by a low body fat reading, missing the signs could well prove fatal.
So even gaining weight easily has its advantages.