Your body’s metabolism, whether you have fast or slow metabolism, has a lot to do with your body weight.
By understanding it, you can make better eating and exercise decisions that align with your body’s needs instead of feeling like you’re fighting against it.
So what exactly is metabolism?
Let’s break it down in a way that’s easy to understand…
Cells benefit from a steady environment
To understand metabolism, it’s important to first understand the concept of homeostasis.
This word comes from homeo, meaning “like; the same; or similar,” and stasis, which means “a state of unchanging balance or equilibrium.”
Putting the two parts of the word together, you get the word homeostasis, which means “a stable unchanging state of equilibrium or a tendency toward such a state.”
Your body, including all its various components (cells, organs, blood, etc.), is attempting to maintain homeostasis. In other words, it’s striving to maintain a steady temperature, keep oxygen levels consistent, provide even levels of glucose in your blood, etc. — keeping everything in as unvarying a state as possible.
The reason for this is that the cells in your body survive, stay healthy, and thrive best when they are in a predictable unchanging environment.
Food is burned to create energy
This brings us to metabolism and its role in maintaining homeostasis in your body.
The biology of metabolism is a somewhat complex thing. But you don’t need to understand all the details to get a good concept of what it is and what it does.
In essence, metabolism involves chemical processing (also known as “burning”) of digested food to convert it into energy that your body needs to survive.
Digested food is distributed to cells throughout your body by means of your circulatory system, which consists of blood vessels through which your heart pumps blood to all parts of your body. Blood carries nutrients and as it flows past cells, they grab what they need from it.
Inside the cells are structures called mitochondria whose function is to burn certain substances pulled from the blood to convert them into usable energy.
The overall rate at which the cells in your body are burning food to produce energy is called your metabolism.
Metabolism directly influences homeostasis
The amount of energy conversion happening in the cells of your body is dictated by various factors, including how much energy is needed by the cells (including tissues and organs) of your body.
But one of the most important factors that regulate your metabolism — which leads to fast or slow metabolism — is the body’s attempt to maintain homeostasis.
The digested foods that your mitochondria burn are mainly in the form of sugars (called glucose) and fats (called lipids). As your cells absorb glucose and lipids from your blood to use for fuel, the levels of these substances in your blood drop. When you eat, you replenish these levels.
Under normal conditions, mitochondria combine oxygen with glucose and lipids to “burn” them and convert them into usable energy. (This, incidentally, is why you need to breathe oxygen to survive.) Just like any other form of burning, this energy conversion process produces heat. This is the primary internal source of heat that keeps your body warm.
From this, you can see that the processing of food into energy by the mitochondria in your cells directly influences, amongst other things, the levels of glucose, lipids, oxygen, and heat in your body. By regulating the metabolic rate (the rate at which your cells are burning food), your body can make adjustments to these levels — all in an attempt to keep them as steady as possible in an ideal quantity to keep the cells happy.
Physical activity improves slow metabolism
As mentioned earlier, the rate of energy conversion occurring in your body — i.e. your metabolic rate — depends on how much energy your body needs for its current level of activity and exertion.
When you are sitting still — reading a book, watching TV, or even sitting at your desk at work — your muscles are undergoing very little exertion and therefore don’t need much energy. So your metabolism tends to slow down to avoid producing more energy than it needs.
On the other hand, when you are physically active — walking, running, playing sports, doing housework or yardwork, etc. — your muscles are expending much more energy and need to replenish that energy. This kicks your metabolism into high gear to convert more food (or stored fat, when sufficient food isn’t available) into energy.
This is why a high metabolism — and activities that keep your metabolism revved up — are helpful in weight loss and maintaining a lean body.
Dieting can slow metabolism
In addition to physical activity, your metabolism is also affected by how much food you are consuming.
When the amount of food you are eating decreases — for example, when you are dieting — your metabolism will tend to slow down as a consequence. Now that you understand the basics of metabolism, this should make sense.
Less food consumed means there is less food for the mitochondria to burn, so you get a slowing down of burning — i.e. a slow metabolism. This is similar to slowing down the rate at which you are throwing logs on a campfire — the fire dies down when there is less fuel to burn.
From this, you can also start to understand why simply going on a diet, without adequate exercise, doesn’t necessarily lead to weight loss. Eating less slows down your metabolism, which means the amount you are eating remains more or less balanced with the amount you are burning. To achieve weight loss, you need to burn more than you are taking in (i.e. have high metabolism with low food intake).
Keeping your physical activity level high while decreasing your food intake is one of the keys to losing weight.
So, overeating is fine, right?
If you’re tracking with this so far, you might be thinking right about now — and it would seem to be a logical conclusion — that eating more food should increase your metabolism to burn up the additional fuel.
Referring back to our earlier metaphor, this would be like throwing extra logs on the campfire. You could expect it to flare up into a large fire to burn those extra logs.
From this, you might conclude it shouldn’t really matter how much food you eat, because your body will always adjust to burning the amount of food you are eating.
Well, unfortunately (or fortunately), there are limiting factors that prevent your body from burning all that extra food you’ve consumed.
One of the major factors that limit this is that the human body evolved in environments where food was scarce. As a result, it has learned to conserve energy and build up as many energy storage reserves as possible.
Excess energy is stored as fat
Your body’s main method of storing energy for later use is to take excess food that is not immediately needed for the body’s current energy needs and convert it to fat. This fat is then stored in various areas throughout your body such as your stomach, thighs, and most anywhere else — including around your abdominal organs.
The fat that is stored out of sight around your organs is called visceral fat. Even if your stomach is relatively flat, you could be packing an unhealthy amount of visceral fat. But don’t be lulled into an “out of sight, out of mind” attitude, because visceral fat puts you at higher risk of serious health complications and diseases such as heart disease, Alzheimer’s, type 2 diabetes, stroke, and high cholesterol.
To avoid packing on fat, it’s important to limit your food intake to only what is required for your current energy needs and remain physically active to maintain an ideal metabolic state in your body.
What is an ideal metabolic state?
The ideal metabolic state would be where your body is efficiently and effectively converting the food you eat into the exact energy needed to support your daily activities and bodily functions.
The mitochondria in your cells play an integral role in maintaining an ideal metabolism for your entire body. To achieve and maintain this, the mitochondria need to be regularly getting the nutrients they need to stay healthy and productive — and to reproduce as needed.
These critical nutrients include amino acids (the building blocks of protein) and fatty acids (building blocks of fats and oils) which cannot be manufactured by the body and need to be obtained through a well-balanced healthy diet.
If your diet mainly consists of a narrow selection of highly-processed foods rather than a wide variety of natural or minimally-processed foods, you run the risk of not providing your mitochondria with sufficient variety and quantities of the nutrients they need to continue operating in top condition.
Junk food can damage your metabolism
Highly-processed foods can poison the mitochondria in your cells, which can sabotage the ability of the mitochondria to maintain an ideal metabolism.
Certain ingredients commonly found in processed foods, such as high-fructose corn syrup and trans fats, have been shown to interfere with a natural process that occurs in mitochondria in which oxygen is used to break down food molecules into smaller units to create energy. This interference can have harmful effects on the mitochondria.
Additionally, the high quantities of sugar, refined carbohydrates, and unhealthy fats found in processed foods create an excess of harmful byproducts — called oxidants — when processed by mitochondria. Too many of these oxidants in your body can cause damage to cellular structures and contribute to the development of various chronic diseases.
Antioxidants are compounds that help neutralize oxidants. You’ve no doubt heard that consuming antioxidants is important for your health, and this is why. You can increase antioxidants in your system by eating more fruits and vegetables.
Another danger of processed foods is that they tend to contain additives and preservatives which have been shown to alter the function of mitochondria and potentially contribute to mitochondrial dysfunction.
The greater percentage of healthy, unprocessed and natural foods you eat — and the fewer amounts of highly processed junk food — the healthier your mitochondria will be. This, along with getting sufficient amounts of physical activity, is the key to achieving and maintaining a healthy metabolism.