So let’s say you are a factory owner/manager. Your factory has a couple of machines and you have some employees, you produce goods. Your buildings heating/lighting and the machines run on fuel, so one of your biggest priorities is to make sure you have a daily fuel delivery. Times are good, you usually use 6 barrels of fuel daily, but your delivery sells you 20 barrels a day. You like it that way, better have some storage for when bad days are coming.
At one point you have more than 500 barrels in storage, you had to extend your storage facilities, which also needs more maintenance, lighting and heating, so your daily fuel usage grows to 8 barrels a day, so you’re storing 12 barrels a day! Your factory is thriving; your storage is still growing and it’s even 1000 barrels now.
One day, disaster strikes. The economy crashes and your daily fuel delivery falls to 2 barrels a day. You’re not worried. Your storage is so big, you can withstand a little hitch like this. You go through 8 barrels a day for some time (6 from your storage and 2 from the daily supply), and after 2 months, you see that your storage has declined significantly. But, you’re not too worried, the economy will become better, so you continue like you always do. After another month you become a bit worried. You have 460 barrels left in storage and if you continue like this, you’ll be out of fuel in less than 3 months. So you decide to change some things. First of all, your big storage is not really necessary anymore, so you shut down part of it, which will decline your fuel usage to 6 barrels a day. But, still a bit worried, you also shut down some machines and fire some of your employees, so your daily usage has come down to 4 barrels a day. 2 from your storage and 2 from the daily supply.
You’re a bit relieved, with this rate, you can maintain your factory and have some output, and can continue for almost 8 months if nothing changes. After 5 months, you have 180 barrels in store, and guess what, the economy is in a rise and your daily delivery has come back to 20 barrels a day! So what do you do… you hire new employees, you go back to your old capacity and you start storing those excessive barrels again. But you don’t need the big storage yet, you’re still at a low point, so you can store up to 14 barrels a day!
The factory = your body (simplified)
So now let’s translate this to our body. The factory is the body, the fuel is the energy that comes in through food. You can see that when more food comes in than you need, the body will store the energy (fat). You can also see that when your storage grows, your body will need more energy, a bigger body needs more fuel to maintain than a smaller body.
When the fuel delivery declines, so when you eat less energy than your body needs, it will take energy from the storage, from the fat. But…. your body becomes smaller with less storage, so it will need less energy to maintain it. You’ll see at that point, the amount of energy you’ll take from the storage will decrease. If we translate this to weight loss: if you lose weight very fast with a diet of 1800 kcal, you’ll lose weight slower once you lost a significant amount of weight, because your body needs less energy to maintain it and will take less fat. BUT the body always wants to preserve as much as possible, so in order to maintain for some time, it will shut down a bit, a bit less energy is needed and losing weight will even go slower, because it takes less fat from your storage.
Ok, so what if you were the factory manager, and instead of getting 2 daily barrels, you got 4 daily barrels. What would you have done? Would you have made the decision to lower the factory ouput? I wouldn’t, I would’ve kept going, kept the same output and kept taking 2 barrels from the storage. Your body also works like that. If you keep that energy coming, it won’t shut down that much and will go in ‘preservation mode’ less fast. Lesson number one: Don’t forget to fuel your body with good energy. Less is not more! Eating not enough can lead to your body shutting down (hairloss, feeling tired, feeling cold all the time, dry skin and a lot more, sometimes subtle symptoms).
So, you can see when the economy was rising again, (or in other words, you stop eating less and go back to your old ways), the body starts storing the energy again, so you start gaining fat. But your body is less big than it was when you started your diet, so you’ll even store your fat faster, because your smaller body needs less energy!
More output = more fuel needed
So now you’re the factory owner and 3 times a week you want a bit more output during an hour. So you stimulate your employees to work very hard during that hour, your machines work on maximum speed, your output is big and you use more fuel in this hour to make everything run. After this hour, your employees go back to their normal speed and the machines run as they normally do. But you know, if you do this too much and don’t take time to rest, build and maintain your machines, they can eventually break down or run less well then they used to do. Your output will decline and your fuel usage will also decrease.
What if you would start building some new machines, it takes some time and energy to build them, but when they’re finished and running, you’ll have a bigger output throughout the day (and a bigger fuel usage) without your employees even having to work harder! And if you would push your employees to work harder for an hour in this situation, your output would even be bigger!
Maybe you already guessed, but this is a simplified version of cardio and weightlifting. What you see is that your body will burn more energy during cardio, but after cardio it will go back to it’s usual state. If you do a lot of cardio, and don’t properly take rest, build and fuel the body, it can breakdown some muscle, which will make your daily energy usage decline. Good for preserving energy, not good for losing weight. So with the weightlifting, you build extra muscle, which will burn more energy throughout the day without doing anything special. If you do a mix of both, you’ll even burn more. Lesson number two: it’s important to do a mix of both weightlifting and cardio to burn energy and to build your body, but equally important is to have enough rest and fuel your body right.
IMPORTANT: this is a simplified way of looking at your body. There are more facets to how the body works. If you have any specific questions, just ask!