How can a person burn more calories per day than consumed? Where did the extra energy come from if food not equivalent to that amount was consumed?
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It comes from stores of fat in your body. Once you’ve used up all of the energy you have eaten.
Body Fat is essentially an energy store, so when you have a calorie deficit, your body will start to break down body fat to get the extra energy it needs.
Here’s the order of operations.
1. You eat. The food you eat is broken down into water, stuff you use for construction (proteins), stuff you use for fuel that day (sugars and fats), stuff you save up for fuel for another day (sugars and fats, but STORED as “body fat”, not burned), and stuff you can’t transform (fibre). It’s not perfect, but that’s the general process.
2. If you don’t eat enough, your body grabs some of the “stuff you use for fuel that day” from the previous “stuff you saved up for fuel for another day”. So if you’re dieting, you’re going to dip into some of your body fat.
3. If you don’t eat enough AND you don’t have any body fat, your body then starts dipping into your already-built construction. It starts burning muscle tissue, because that’s all it has to keep operating. (This is why people look like sticks during famines).
So, yeah, body fat’s the answer.
Our bodies require a certain amount of energy (in the form of calories) to perform basic functions like breathing, maintaining body temperature, and circulating blood. This is called our resting metabolic rate. In addition, we burn extra calories through physical activity and exercise. Just simply being alive takes a solid chunk of energy.
If a person burns more calories per day than they consume, it means they are in a calorie deficit. This deficit can come from either reducing calorie intake (i.e. eating less) or increasing calorie expenditure (i.e. exercising more).
When we are in a calorie deficit, our bodies start using stored energy (like fat) to make up for the deficit. This is how weight loss occurs. The extra energy comes from these stored energy reserves.
You use the energy stored in your liver and the energy stored in fat if there is no available food for you to breakdown.
That’s the whole premise of weight loss. If you burn more than you eat you start burning fat/muscle. That’s how you lose weight
It comes from you. That’s literally what weight loss is.
Your body coverts fat stores into energy that your body then uses.
It comes from food you’ve eaten in advance.
What happens on the weekend when you go to a store and buy something with cash? You didn’t earn any money that day. You are spending cash you accumulated in the past and saved up.
All the fat in your body is food you ate one day and didn’t need that day, so your body saved it for later. When you eat a deficit, that’s the “later”. Your body dips into its savings to spend the extra energy you need.
Wait, for all the answers that says you burn fat, this is assuming there are no glycogen stores? It would also depend what activity is causing the caloric deficit? Wouldn’t higher intensity mean carbs/sugars were burned first?
Your body gets its energy a few different ways:
– Sugars (carbohydrates) get converted into glucose.
– Fats turn into fatty acids and glycerol.
– Proteins turn into amino acids.
These parts then swim around in your blood or other body fluids. Your body treats this like a sushi boat and takes what it needs:
– Cells in your body grab glucose or fatty acids to use as fuel.
– Your liver is like a “sugar battery.” It stores some glucose as a backup. When you need more sugar in your blood, the liver turns this backup into glucose. When there’s extra sugar, the liver stores it again.
– Your fat cells are like a “fat battery.” They convert any excess energy fat, and store that fat into fat cells (adipose tissue). When you need more energy, these cells turn the stored fat back into something your body can use as fuel. Your fat battery is a lot slower than your sugar battery.
– Sometimes, your body can use amino acids from proteins as a backup fuel. It can even turn them into a little bit of sugar or fat if needed.
So, when you’re using more energy than you’re eating, here’s what happens:
– Your body uses the sugar in your blood first.
– Your “sugar battery” in the liver kicks in to keep you going.
– Your “fat battery” starts to slowly give you more energy.
– If needed, your body can use protein as a last-resort fuel.
You can live quite a while just using your “fat battery” for energy.
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