During our nightly rest, our brains have a vital mission, to repair everything that went wrong the previous day. That is when our muscles, joints, and vital organs are restored, and it’s one of the reasons why we feel refreshed in the morning.
Every little process in our bodies requires energy. When you do a simple movement of an arm, it involves the activity of your brain in making a decision to move, firing signals through neurons, and finally activating muscles, which results in a hand gesture you were trying to make. Some people don’t understand this, but there are millions of cells involved in this, and every single one of them requires energy.
Metabolism represents the reactions that happen in our bodies, and it is defined by two parts. Katabolism is burning of the more complex molecules, during which we get energy, and anabolism represents reactions in our bodies where smaller chemicals are used to create building blocks for our bodies, such as proteins, amino acids, and fats.
We get our energy from food, that is constructed of proteins, carbohydrates, and fats that we burn down or store once they enter our body. The amount of energy that food provides us with is mostly measured in calories. Most energy-related processes happen in the mitochondria, and that’s where it got that nickname “the powerhouse of the cell.”
Most people think that their body and mind are inactive while sleeping, which is not true as our brains are active during sleep, and our body still requires energy to function. During our nightly rest, our brains have a vital mission, to repair everything that went wrong the previous day. That is when our muscles, joints, and vital organs are restored, and it’s one of the reasons why we feel refreshed in the morning.
Energy expenditure depends on many factors. It is the highest in newborn babies, as their growth rate is incredibly high. Infants double their size in the first six months of their lives, and at the end of the first year, they grow as much as three times. After that, the growth rate is slowed, and then it bursts again in the adolescence, which affects energy expenditure. The elderly need less energy to maintain their body functions, and this amount starts dropping after 40 years for men, and usually after menopause at about 50 years for women.
The amount of energy spent is also affected by your sex. Males spend 16% more power than females, and that is mostly attributed to different hormonal statuses, and different compositions of the bodies. Energy expenditure depends on metabolism and fitness levels as well. People who have more muscles and less fat spend more energy on average. Muscles burn more calories and require more energy to maintain, so that’s why fit people need to ingest more calories than inactive people. That is part of why men need more energy, as they usually have more muscle, while women have a bit more fat stored on average.
Humans need energy for the following:
At the beginning of sleep research, the idea was that the sleep was a state in which we were inactive, in it passively served to conserve energy. Nowadays, studies are showing something completely different. Our brain is very much active during this period, and it is doing the needed housekeeping. Also, this is the time when our memories and knowledge are consolidated.
We spend 90% of the energy during sleep that we usually spend during the awake resting period, or we spend 0.9 of our BMR. There haven’t been considerable differences observed in energy usage, between different stages of sleep, but there haven’t been too much research done in that area either.
Out of all the energy we use, 20% goes to brain energy consumption. That is an extremely high amount for an organ that is that small. But that shows you how important the central nervous system is, as no function in our body can go without its supervision.
A calorie is a standard energy measuring unit, and it is defined as the energy needed to increase the temperature of 1 kilogram of water for 1 degree Celsius. On average, a 125-pound person spends 38 calories per hour while sleeping, a 155-pound individual spends 46 calories an hour, while a 185-pound person burns around 56 calories per hour. You see that the more you weight, your BMR is higher, and the more energy you need to maintain your body. These numbers might not be correct for everybody, as there are a lot of different factors affecting that other than body weight.
If you spread these numbers to a whole night of sleep, ranging between 7 to 9 hours, you get that a 125-pound person burns 266-342 calories, a 155-pound person burns 322-414 calories, while a 185-pound person spends 392-504 calories each night.
Metabolic equivalent (MET) is an objective measure of metabolism rate during some activity compared to a sitting and resting state. The more physical the action, the more energy, and oxygen are used, and the higher the MET will be. Here is the list of some activities, and the energy required for them:
| Activity | MET | Energy usage (Described in calories, for a 30-minute activity for a 70 kg man) | Energy usage (Described in calories, for a 30-minute activity, for a 57 kg woman) |
| Mild | |||
| Playing accordion | 1.8 | 66 | 54 |
| Horseback riding | 2.3 | 85 | 69 |
| Playing piano | 2.3 | 85 | 69 |
| Billiards | 2.4 | 88 | 72 |
| Golf (with cart) | 2.5 | 92 | 75 |
| Walking (2mph) | 2.5 | 92 | 75 |
| Dancing (ballroom) | 2.9 | 107 | 87 |
| Voleyball (noncompetitive) | 2.9 | 107 | 87 |
| Moderate | |||
| Walking (3mph) | 3.3 | 121 | 99 |
| Cycling (leisurely) | 3.5 | 129 | 105 |
| Calistenics (no weights) | 4.0 | 147 | 120 |
| Swimming (slow) | 4.5 | 165 | 135 |
| Walking (4mph) | 4.5 | 165 | 135 |
| Vigorous | |||
| Chopping wood | 4.9 | 180 | 147 |
| Tennis (doubles) | 5.0 | 184 | 150 |
| Ice skating | 5.5 | 202 | 165 |
| Cycling (moderately) | 5.7 | 209 | 171 |
| Dancing (ballet) | 6.0 | 221 | 180 |
| Surfing | 6.0 | 221 | 180 |
| Roller skating | 6.5 | 239 | 195 |
| Skiing | 6.8 | 250 | 203 |
| Climbing hills | 6.9 | 254 | 206 |
| Swimming | 7.0 | 257 | 209 |
| Climbing hills (5kg load) | 7.4 | 272 | 221 |
| Walking (5mph) | 8.0 | 284 | 239 |
| Jogging | 10.2 | 375 | 305 |
| Squash | 12.1 | 445 | 362 |
Because you burn fewer calories while sleeping than being awake, some people thought that it would be a good idea to skip sleep and stay awake instead, as that would lead to more calories burned and losing weight. Don’t do this, as it is not good for your health, and it won’t even have the desired effects. Lack of sleep affects leptin and ghrelin, the body’s hormones in charge of hunger. When you are sleep deprived, their production is all messed up, so you will eat more, and you will gain weight. Not only do you crave more food when you are sleep deprived, but you are also more likely to for full of sugars unhealthy meals. Lack of sleep also increases the levels of cortisol, a hormone that is stimulating your body to store more energy as fat.
There are a few things you can do to help boost your metabolism.
Dusan is a biologist, a science enthusiast and a huge nature lover. He loves to keep up to date with all the new research and write accurate science-based articles. When he’s not writing or reading, you can find him in the kitchen, trying out new delicious recipes; out in the wild, enjoying the nature or sleeping in his bed.
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