This is part 3 of a series. If you want, you can read from the beginning.
The information in this section has been inspired by Dr. Jason Fung. If I may, I will borrow his analogy of various kitchen appliances to explain how energy is stored in the body.
If you’ve been living on this planet for some time you’ve probably heard about the “calories in and calories out” concept. This school of thought says that your body requires a certain amount of calories per day to operate, and that losing weight is a straightforward maths problem where you simply need to put less calories into your body than you need, to lose weight. If you manage to eat less calories, or exercise, calories then you should lose weight.
The problem with this concept, or idea, is that the body just doesn’t actually work that way.
How many times have you gone on a diet and counted calories, and probably exercised diligently, only to see the weight fall away, only to eventually come back again? Almost nobody ever manages to lose weight and keep it off by restricting calories this way.
Why then do we keep hearing the same tired old advice over and over again, when it clearly doesn’t actually work in the real world?
Your body is not just a single compartment where energy flows in, fills up, and then empties out over time.
So why is the one compartment idea wrong, and why can’t most of us really lose weight by counting calories?
Well, your body is a very advanced machine, and it knows how to use three different types of energy sources. The main two sources of energy are glucose, and fat. The third type is protein and can be thought of as emergency energy for extreme situations.
If you have a lot of fat then your body will barely ever mess with your protein stores and will instead preferably operate on glucose and fat. We’ll talk more about protein in a later section, so we’ll focus more on glucose and fat for now.
The way your body stores energy really is more like two compartments. When you eat carbohydrates (sugar, bread, rice, pasta, potatoes etc.) this is very quickly converted to glycogen and stored in the liver. The liver can only store a limited amount of glycogen and fills up quickly. It’s kind of like your refrigerator at home where you store relatively small amount of things in it for short amounts of time.
If you go shopping and bring home an extra large amount of groceries then you’d fill up your fridge, and after that you’d probably have to store some of the groceries in your freezer. The same thing happens with glucose that you consume – the liver gets filled up and then the excess energy is stored as fat. Any fat that you eat also goes straight to your fat stores.
Your fat stores are your long term storage for energy, and a practically unlimited amount of fat can be stored on your body. If you’re like me, then you probably have a lot stored up.
The interesting part, is that when you consume energy you use up your glycogen first. This is a built in behaviour and is the same for everyone. Your glycogen gets used up first, and then you go to your fat stores (the “deep freeze”) to tap into your emergency energy. If we didn’t have fat stores then we’d die very quickly once we ran out of glycogen, so it’s a good thing we have them.
If you want to lose fat, then the only way to do that is to use up all the energy you have stored as glycogen first. However, if you keep topping up with new glucose all day long by eating meals and snacking then you’ll never be able to access the fat stores.
“But, wait!” I hear you thinking, “If we just put less food into the fridge won’t it eventually just empty out and we can access all the stuff in the freezer?”
This is a great point, and is really a very important point, and it’s the main reason that “calories in and calories out” is pretty much just nonsense.
For most people, as you empty out the fridge and use up all the stored glycogen, your body senses this and starts conserving energy by making you feel hungry. You’ll probably also not feel like moving very much and will want to sit down and watch tv, or have a sleep. If you keep going with not re-stocking the fridge them your body will reduce your metabolic rate.
Oh no! Are we doomed then? No, we’re not. Fortunately our body does have a built in mechanism for deciding whether or not our fat stores can be accessed once the glycogen is all used up. This mechanism is the hormone insulin and we’ll talk about that next.