Metabolism – the truth about it

It is in everyone´s mouth lately – metabolism. Good and bad, fast and slow. But what is it actually. What is true about alle the rumours, what do you need to know about it? Let´s talk about all of that. In this blog post I am going to cover the definition, explain how the metabolism works, what the metabolic rate is and give insights into the topics: “spicy food, lemon water and green tea”, “intermittent fasting “and last but not least: “dieting and metabolic damage”


The Metabolism is defined as the sum of all of the chemical reactions within the human body. This includes any chemical process by which a substance is broken down (catabolism), produced (anabolism), or chemically modified. Often the metabolism is described in terms of food and nutrient use within the body, primarily because it is simpler to understand.

Every living thing has a metabolism, from a bacterium to a plant to you, But in this blog post I am only going to address the metabolism in regards to food and nutrients.

how does the metabolism work?

The metabolism is made up by two biochemical reactions: The catabolism and the anabolism. The anabolism are building processes whilst catabolism referres to processes that break something down.


Imagine you are eating a piece of pizza: The slice contains many key nutrients that are essential for life: proteins, starches and fats. In order to use the essential nutrients the body has to break down the proteins and starches into smaller components like amino-acids and sugars. This is also what we understand by “digestion” – we break down the food into it´s smallest components to make use of it.

The body needs amino-acids for example for muscle and tissue growth, the immune system and hormones. Sugars are essential for energy and fats for the production of hormones and energy as well.


After breaking down the food into their smallest components, we use the the materials to produce the ones we need. For this the smaller “building blocks” the body just broke down from the food (catabolism), are then joined together differently to build structures in the cell, or even to help build new cells.

But no energy transfer is 100% efficient. So no all the energy that gets broken down is also going to be used efficiently to build up new components. Every time the energy changes it´s form, a small amount is converted into a non-usable form – for example heat. (for example night sweats)


the metabolic rate

Your metabolism varies, depending on your age, gender, activity level, fuel consumption, and amount of your lean body mass. Cause of these factors your metabolic rate varies throughout your life.

Simply said the metabolism rate is the amount of energy (within a set time) your body needs to hold it´s homeostasis upright. With other words: it indicates how long your body needs to break down fuels and build up new ones to keep your organisms functions running.

the basal metabolic rate

Shortly said: the baseline of an organism. It is the part of the metabolic rate, an organism needs at rest: calm, unstressed, in a thermoneutral environment and not actively digesting food. Basically what your body needs to keep all necessary functions up (when at complete rest!!).

As I mentioned before – this varies from person to person depending on your age, fuel consumption, lean body mass (muscle-fat tissue ratio), stress, how tall you are, …

TW (calories mentioned, skip the next part if any kind of numbers are triggering for you)

Human adult males typically have a BMR of 1600-1800 kcals/day, and human adult females typically have a BMR of 1300-1600 kcals/day. That doesn’t mean that’s all the calories you should eat or need, though! Most people have a higher metabolic rate than this just from carrying out daily activities like standing up, walking around, eating and working or studying.

Physical Activity Level

As the name already says: this referres to the energy an organism burns when being active: walking, working out, eating, … The more active someone is the higher is the metabolic rate. It makes sense: when you are more likely to be hungry, when you are running up a hill rather than sitting at your desk. The average adult has a metabolic rate of 1.5x of the basal metabolic rate. (For instance someone with a basal metabolic rate of 1600kcals/day, needs 2400 kcals just to maintain it´s weight)

Even when tough you´re burning more calories the more active you are – this should not be the goal. Physical activity is good and healthy up to some amount. You don´t have to work out and go for long and draining walks for hours to maintain your body weight. The goal is to be in tune with your hunger and fullness signals, so your body can tell you exactly how much you need.

Unravelling myths

1. Spicy food, lemon water and green tea

Spicy food – it´s a fact that when you are eating spicy food, it builds up heat in your body, which the organism is going to regulate against in order to maintain its´ homeostasis. But we are speaking here about a very insignificant amount, it really doesn´t change much. Trust your taste buds – after all the satisfaction-factor plays a greater role when it comes to feeling good in your body and your eating behaviors.

lemon water – it´s a myth. Drinking lemon water is doing absolutely nothing regarding to your metabolism. It´s a fun way to add some flavour to your water but it´s nothing more than a trend.

green tea – Green tea has a modest thermogenic effect, meaning that it can increase the amount of calories that your body burns via heat. However, these effects are so minor it is actually not worth being mentioned.

There is no food that is going to significantly speed up or slow down your metabolism to such an extent that you should actively pursue eating or not eating them.

2. dieting and the metabolism

Restrictive diets (either calorie or food diversity wise) can disrupt your metabolism. It is adaptive – so when you are restricting calories, it adapts to the less energy and slows down the metabolism. It doesn´t mean it´s broken or ruined. By eating more consistently again, it will adapt to this situation as well. Not eating a wider range of foods can lead to malnutrition and a lack of nutrients/minerals/vitamins, which can disrupt the homeostasis. So restricting calories or any kind of food (especially carbohydrates and fats), can slow down your metabolism.

detoxing and metabolic “therapy”/diets do not work. Just such as any other diet.

3. intermittent fasting to speed up the metabolism

Speaking about diets – let´s also address intermittent fasting. Because that´s a diet as well. The harsh truth is: your body doesn´t care, when you are eating. Fact is, when you are going without food for too long and you´re carbohydrate storages are empty, your body catatabolises itself and shuts down not so much life-essential functions. Such as producing hormones (wrecks with your hunger, fullness and satiety, your period, …)

Focus on eating real and nourishing meals and add snacks whenever needed (very essential in recovery from an eating disorder!) and your metabolism will just do it´s work the way it is supposed to.



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