17 Facts About the Metabolism That Will Teach You How to Stay Healthy
Knowing these facts about how the metabolism works will help you stay healthy
The metabolism is one of the most important functions in the human body but is also an extremely misunderstood function. Here are 17 facts that will give you a better understanding of the metabolism and in the process help you understand how to better keep yourself fit and healthy.
The metabolism is not an organ, it is the name for a group of chemical reactions
Most people think the metabolism is like an organ or something. It is not. The metabolism is the name for the numerous complex chemical reactions that happen inside each cell where calories are transformed into the required fuel to keep us alive.
That means every cell has its own metabolism i.e. chemical reactions which transform calories into fuel. Though a better way to imagine it is that each cell metabolises the compounds that our body sends to it so as to transform them into what is needed to keep us functioning.
The metabolic process is complex — really complex
After we eat food, the digestive system uses enzymes to firstly, break proteins down into amino acids, to secondly, transform fats into fatty acids, and to thirdly, transform carbohydrates into simple sugars.
These compounds are then absorbed into the blood which carries them into the cells. Once they enter the cells, the cells begin metabolising the compounds i.e. reacting with them, to release energy either for use now or to be stored in the tissues for later use — the latter is how fat is built up.
So, our cells metabolise calories to transform those calories into energy, some of which are used right away and some of which are stored for later use. The more that is stored for later use, the more fat that a person will build up.
The metabolism involves two kinds of reactions that go on at the same time
The metabolic reaction is made up of two reactions, a catabolic reaction and an anabolic reaction. A catabolic reaction is a reaction that produces the energy needed for cells to do what they need to do. So, it transforms calories into energy which can be used for anything from heating the body to basic muscle function and much more.
An anabolic reaction is a reaction that takes energy from the catabolic reaction and uses it to build new cell tissues and create energy stores for future use. So, it’s about supporting the growth of new cells, the maintenance of body tissues, and most importantly the storage of energy for future use.
The reason some people struggle to lose weight is that their body focuses too much on the anabolic reaction, so the part which stores energy for future use i.e. rather than just burning off excess calories through a catabolic reaction, it saves all excess calories for future use by anabolising them.
The metabolism is controlled predominantly by the endocrine system and the pancreas
Metabolic rate is controlled by several different hormones from the endocrine system, with the pancreas deciding whether the catabolic or anabolic reaction will be dominant at any present time. Typically, after eating there is more anabolic activity than at any other point because our body is working to transform those calories into energy stores for future use.
However, in some people, their bodies have less anabolic activity all-round than others which is why they find it easier to manage their weight. So, if you struggle to keep weight off or manage your weight, blame your pancreas.
The vast majority of our calorie intake is used to keep us alive — this is why weight loss can be so difficult
The number of calories required for our bodies to keep their basic functions functioning is called the basal metabolic rate — also known as the resting metabolic rate. The resting metabolic rate relates to how many calories our bodies utilise while doing absolutely nothing i.e. how many calories we would need to keep our body functioning if we did nothing throughout the day.
The average person is required to expend between 1,500 and 2,000 calories a day even if they do absolutely nothing. That means we utilise between 60 and 80 percent on average of our calorie intake just to fuel basic bodily functions.
On top of that, we also use a further approximately 10 percent of our calorie intake to transform food into energy. So, the metabolic reaction expends 10 percent of all calorie intake to transform those calories into energy.
This means in total people use between 70 and 90 percent of their average calorie intake just to keep their bodies functioning, which means we only use approximately 10 to 30 percent of our average calorie intake for physical activity.
This means that 500 calories of stored energy can provide us with fuel for a hell of a lot of physical activity, which is why burning off fat for many people can be so difficult i.e. when it comes to physical activity, a small number of calories above our basal rate gives us a lot of fuel.
There technically is no such thing as fast or slow metabolism
What is a fast metabolism and what is a slow metabolism? From reading the previous points, many may assume it is how fast the metabolic reaction is. However, that is not the case.
Imagine two 12 stone men of the same height, one of these men has a basal metabolic rate of 1,500 calories a day, and the other has a one of 1,700. The one with 1,700 has the “faster” metabolism. That’s because this man while doing nothing would burn off 1,700 calories a day, while the other man would only burn off 1,500.
This would mean that the man who needs 1,700 calories just to function would have to eat more to put on weight than the man who required just 1,500. However, the reverse is also true, the man who needs 1,700 calories just to function would not need to cut down as much to lose weight.
So, a “fast” metabolism is a metabolism that — on a pound-for-pound basis — expends more calories while doing nothing than the average, and a “slow” metabolism is a metabolism that — on a pound-for-pound basis — expends fewer calories while doing nothing than the average.
The reason we call the former a fast metabolism and the latter a slow is that they are the simplest way to explain the extremely complex reality that has just been explained i.e. some people burn through calories faster because they use more on a pound-for-pound basis and some people burn through them slower because they use fewer.
You technically can’t speed up or slow down your metabolism, you can only change the balance between your weight and your required calorie count
If you eat a lot and pack on a lot of fat you will need more calories to sustain yourself. If you work out a lot and eat healthily and put on a lot of muscle you will need more calories to sustain yourself. However, it’s more complex than that.
If you utilise the former method, you will “slow” your metabolism because on a pound-for-pound basis you will need fewer calories to fuel your larger size. On the flipside, if you use the latter method you will “speed” up your metabolism because on a pound-for-pound basis you will need more calories to fuel your larger size.
This is because more muscle and less fat equal a higher energy usage for your body weight, whereas more fat and less muscle equal a lower energy usage for your body weight.
That means you never speed up or slow down your metabolism per se, you just alter the number of calories you need to sustain yourself compared to your body weight i.e. the more calories you need and the less weight you have, the faster your metabolism, the fewer calories you need and the more weight you have, the slower.
Food does not speed up your metabolism
When people say if you eat this it will “speed” up your metabolism they are spreading misleading information. Yep. Food cannot speed up your metabolism because it plays no effect on your basal metabolic rate.
Technically, some foods, due to us requiring more energy to process them, will increase our energy burn rate while we process them. But it’s negligible and not much use in weight loss.
Also, this increased burn rate is only because unlike most foods, which cost us 10 percent of the food’s calorie count to transform it into useful energy, these foods cost us more than 10 percent i.e. we get less energy from the food because we use more energy to transform it into useful energy.
That means if you’re hoping that eating certain foods will speed up your metabolism, unfortunately, you are likely to be sorely disappointed. Only by eating healthy food and losing fat content and increasing muscle content through exercise can you speed up your metabolism.
Building muscle and losing fat are the best ways to speed up your metabolism
The brain, the liver, the kidney and the heart account for approximately half of the energy we burn while at rest. The body’s muscles largely account for the rest though fat and the digestive system also play parts.
This is why the more muscle and fat you have the higher your basal metabolic rate i.e. the more calories you need to eat each day to keep your body functioning.
But — like said earlier — because muscle burns more calories than fat, inevitably the more muscle you have and the less fat you have, the easier it is to burn calories because your basal metabolic rate on a pound-for-pound level will be higher, meaning you need a higher fuel requirement to fuel your body making it easier to both lose weight and keep weight off.
That means the more muscle and the less fat, the easier it is to stay fit and healthy and burn off excess fat, the more fat and the less muscle, the harder it is to stay fit and healthy and burn off excess fat. Yep, fat loss truly is extremely difficult.
Note: this is why men typically find it easier to lose weight than women, men naturally have a lower fat level than women do and more muscle. This combination gives men a fat-burning advantage because it means they can burn off more calories both while at rest and through exercise when compared to women.
A fast metabolism does not necessarily mean a person will be thin
Many studies have found that some people who are overweight have fast metabolisms, meaning a fast metabolism does not necessarily per se mean a person will be thin. The reason being, some people — due to their fast metabolisms — burn through calories so fast, to compensate they ate a lot, which causes them to put on weight and keep putting on weight.
So, they need more calories to keep functioning and so overcompensate by eating too much. This means one of the key factors behind people who find it easier to manage their weight, is that for some reason their desire for food is more closely matched to their required calorie needs than those who find it difficult to manage their weight.
That means often, one of the main reasons why people struggle with their weight is that their desire for food is greater than the number of calories their body actually needs.
In terms of why many people are this way, it is believed to be because most people historically lived in a world of undernutrition and so needed extra motivation to go out and find food. So, that extra motivation to eat more used to be helpful, now it’s not.
No one is sure why some people have evolved to struggle to burn off fat while others have evolved to find it hard to put on weight — but the immune system is believed to be the key
Some people find it virtually impossible to burn off fat and scientists are unsure why this is. But some theorise it’s because like said that our bodies are trying to protect against undernutrition.
So, due to an erratic diet in which people go through periods of decent nutrition and periods of undernutrition, to protect against the periods of undernutrition, some people have evolved genetic processes to hold on to their fat to protect them during these periods.
It’s believed by many that the immune system is at the core of this response. So, if we suffer a period of undernutrition, the immune system begins to anabolise more of our calories as fat to store for future reserves to try to cope with future periods of undernutrition. The more erratic the diet i.e. the more periods of undernutrition, the more the immune system will try to do this to cope with the periods of undernutrition.
But this only happens in some people — most people in fact. What happens in others, those lucky few who can’t seem to put on weight no matter what, is that their immune system seems to do the opposite. It seems to be designed, rather than to protect against undernutrition, to protect against overnutrition.
That means their bodies don’t hold on to excess calories, they burn them off. This is typically why those with metabolisms like this don’t handle undernutrition as well as those who struggle to keep weight off.
It should be noted that many dispute these arguments, asking the question of why we are not all one way or the other? But, in response, it is argued that that is because some have lived in areas where food has been abundant, and others have lived in areas where access to food has been erratic.
It’s believed that the people who struggle to put on weight are likely linked to ancestors who have predominantly lived in a world of good and consistent nutrition, and so have needed to develop a system to burn off excess calories. Those who struggle to keep weight off, on the other hand, are likely linked to ancestors who predominantly lived in environments of poor and inconsistent nutrition, and so have evolved the means to cope with that by storing any excess calories as fat.
The reason most people struggle in the modern world with their weight is likely that historically there are not many places that offered abundant access to good and consistent nutrition, so inevitably most people are better suited to handling undernutrition rather than overnutrition.
The key to weight management is matching calories to energy requirements
For the majority of people, what will define whether they are a healthy weight or not is whether they consistently eat a healthy diet that matches the calorie count that their body requires.
That means one of the key factors for attaining and keeping to a healthy weight is working out how many calories your body needs to sustain itself. The fact that this is so difficult is why many people struggle to maintain a consistent weight.
Fidgeting is a common sign of not just a fast metabolism, but also a metabolism that keeps weight off
One of the most common trends seen in people who struggle to put on weight — no matter how much they eat — is fidgeting and hyperactivity. It’s believed this fidgeting and hyperactivity is how these people’s bodies respond to having eaten above their required calorie count.
So, when they eat above their needed calorie count, rather than their metabolisms anabolising the excess calories and storing those calories as fat — which happens in the majority of people, even those who just have fast metabolisms — their metabolisms instead catabolise the excess calories, flooding the person with excess energy which they need to burn off. One of the ways they do this is through fidgeting and hyperactivity.
That means if you see somebody fidgeting all the time, and they are thin. The probability is that their body does not store excess calories as fat, it demands that they burn that excess energy off.
Note: if a person with a metabolism like this eats a calorie count way above their required level, it can cause real problems with both their insides due to the excessive speed with which their body will process the food i.e. they will likely empty themselves frequently. It also can have a very detrimental effect on their mental health. This is because the body becomes so hyper due to the flood of energy that their body demands they burn off, it can send their emotional state haywire. In some people, it can even cause a form of mania. It also, once the energy has been expended, can cause the kind of energy crashes and mental crashes that follow mania. Yep, there are downsides to being able to eat as much as you want.
Fidgeting does not guarantee a person has a fast metabolism
Fidgeting as a sign of a person with a fast metabolism is not a perfect science. In some people, they have fast metabolisms and are fidgets which helps them burn off more calories, but even still they can’t eat anything they want and expect not to put weight on.
So, fidgeting does not necessarily mean a person will be thin, nor does it even mean they will have a fast metabolism. People with slow metabolisms can be fidgets. It’s just most people who are super fidgety have a metabolism that demands they burn off excess calories, and that is why they are so fidgety — especially after big meals. So, it’s a good rule of thumb for identifying them.
Our basal metabolic rates begin to slow from a young age
Once we are past the age of 18, our metabolic rates begin gradually slowing. That means our basal a.k.a. resting metabolic rate decreases as we age, so we need to burn fewer calories to stay alive. This reality perplexes scientists to this day, and nobody can explain why we need to burn fewer calories to stay alive the older we get despite having all the same functions as we get older.
Some link it to the fact that we produce fewer cells as we age and have less muscle and typically more fat but the maths doesn’t seem to add up even when taking into account these losses. It seems our bodies just for some reason get more efficient and so require fewer calories to keep us going. This is of course why as we get older, it can be even more difficult to keep off weight and lose weight.
Crash diets can be disastrous — they can permanently decrease our basal metabolic rate and make us want more food forever
The body fights very hard to stop itself from losing weight, so when a person achieves a consistent calorie deficit and so begins to lose weight, small changes start to happen, most notably increases in hormone levels and changes in the brain. These changes lead to increased feelings of hunger and decreased food satisfaction feelings.
That means dieting — especially crash dieting — makes you less satisfied with food and makes you more hungry, and these feelings continue even after you have ended the diet. On top of that, there is a slowing of the metabolism. Specifically, the resting metabolism. That means dieting causes your body to adapt and require fewer calories to function while at rest, and it does this to a higher level than any fat loss could account for. This change will be permanent.
The reason this happens is that our bodies get used to a certain body weight and start to worry when we go below that body weight. So, what it does is when we start losing weight, it starts to make us feel more hungry to try to inspire us to eat more, and it doesn’t stop making us feel this way even after we are once again eating more. It also makes certain that we can survive with fewer calories — because it assumes food availability must be scarce — and so it doesn’t change this once we start eating more calories.
So, it makes us able to survive with fewer calories but motivates us to fight to have even more calories. The reason it does this is that it wants to make certain we never achieve a calorie deficit again i.e. by making us permanently want more food despite needing less food it aims to inspire us to work harder to ensure we don’t ever have a calorie deficit again.
A consistently healthy diet is the best way to manage your metabolism
It is true that if you wish to burn off fat you will need to achieve a calorie deficit. It is the only way to lose fat. But that calorie deficit should always be a slight one. So, gradual weight loss is the best way to protect yourself against the chemical changes that weight loss can cause which make weight loss — and keeping weight off in the future — ever more difficult.
That means consistently eating a healthy diet that matches your required calorie count is the best way to ensure your metabolism always works for you rather than against you, and the aim should always be to only ever slightly deviate from that count, either for weight loss or weight gain.
Final words
The human metabolism is complex as likely this post has shown, which is often why losing weight for most people can be so difficult. But the one tried and tested method that will work for everyone is exercise and eating a healthy diet.
No matter who a person is, if they consistently eat a healthy diet in which the calorie count matches their body requirements, and they consistently exercise, then they will end up healthy. That means there are no shortcuts because crash dieting and sudden explosions of intense exercise — which can mimic the effects of crash dieting — in most people simply create short-term gains for long-term losses.
That’s all from me, thanks for reading! If you enjoyed this post, you may also enjoy the following:
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