If you’ve ever spent any time scrolling through the health and wellness corners of social media, you’ve probably seen a number of products claiming to improve your metabolism. But what exactly is your metabolism? Everything you expose your body to—from lifestyle to airborne viruses—affects your physical characteristics, like your blood pressure and energy levels. Together, these biological characteristics are known as your phenotype. And the biological system that most directly affects your phenotype is your metabolism.
So if you’re eating something, taking medications, smoking, or exercising, your metabolism is responsible for transferring that biological information into your body to adapt.
metabolism is energy conversion
Your metabolism consists of a network of thousands of molecules and proteins that convert the food you eat into energy and building blocks that your body uses to move, grow, and repair. At the chemical level, energy metabolism begins when the three macronutrients – carbohydrates, fats and proteins – are broken down atom by atom to release electrons from chemical bonds. These electrons charge components in cells called mitochondria.
Similar to the way batteries work, mitochondria use this electrical potential to create a different form of chemical energy that the rest of the cell can use.
Simply put, the primary role of metabolism is to convert chemical energy into electrical energy and back to chemical energy. How this energy moves throughout the body can play a central role in determining whether you are sick or healthy.
I’m a biochemist who studies the different networks of metabolism that are used during transformation in your body. My team and I have been able to define specific characteristics of metabolism, such as the presence and amount of certain metabolites – products formed from breaking down macronutrients – under different conditions.
These conditions include diseases such as COVID-19, diabetes, multiple sclerosis and sickle cell anemia to experiencing unique environments such as radiation exposure, high altitude, aging and sports performance. Each of these settings affects which parts of your metabolic network are used and how they communicate with each other.
Elite athletes set upper limits
Given the alarming increase in obesity and the associated metabolic syndrome – nearly 1 in 8 people worldwide were living with obesity in 2022 – defining a healthy or impaired metabolism can help identify whether What went wrong and how to address it.
Elite athletes offer a prime population to best study metabolic function, as their networks of molecular and chemical reactions must be finely tuned to compete on the world stage.
Traditionally, lactate threshold has been an important measurement of athletic performance by indicating the intensity of exercise when lactate begins to rise in muscles and blood.
Contrary to popular belief, lactate is not only a waste product but also an energy source, and it accumulates when mitochondria can produce it faster than it can. While a moderately active person may reach their limit at an exercise intensity of about 2 watts per kilogram, typical cyclists can maintain an intensity of about two to three times higher.
When comparing the lactate thresholds of a group of elite cyclists, we found that cyclists with higher thresholds had better markers of mitochondrial function. One of these markers was higher production of coenzyme A, a molecule that shuttles carbon around cells and is important for breaking down carbs, amino acids and fats into chemical energy.
It appeared that high performing cyclists burned more fat and burned fat for longer periods of time during the multistage world tour than low performing cyclists.
Dysfunctional metabolism in diseases like Covid-19
If you get a serious illness like COVID-19, your metabolism also changes.
Unlike typical cyclists, COVID-19 patients have an impaired fat-burning ability that persists with long-term COVID. The blood of these patients at rest is similar to the blood of a typical cyclist at the time of exertion. Considering that exercise intolerance often accompanies prolonged COVID, this suggests that mitochondrial dysfunction may play a role in COVID-related fatigue.
Burning fat uses a lot of oxygen. Covid-19 damages red blood cells that deliver oxygen to the organs. Because red blood cells have a limited ability to repair themselves, they may not function well during the remainder of their approximately 120-day lifespan. This may partly explain why Covid symptoms last so long in some people.
blood donors define the middle
Blood transfusion is one of the most common clinical procedures. More than 118 million pints of blood are donated by millions of people around the world every year. Because blood donors must undergo screening to ensure that they are healthy enough to donate, they are generally moderately healthy, somewhere between severe disease and typical athletic performance. Blood donors from all walks of life also have the same variety of biological characteristics as the study population.
My team and I looked at the blood of more than 13,000 blood donors to shed light on their metabolic diversity. We found specific characteristics that can predict how well a donor’s blood will work in patients, which also have an impact on how well the blood works in donors.
We found that one of these symptoms is a metabolite called kynurenine, which is produced by the breakdown of the amino acid tryptophan. We found that blood from donors with high levels of kynurenine was less likely to restore hemoglobin levels in transfusion recipients than donors with low kynurenine levels.
Kynurenine levels are higher in older donors and donors with a higher BMI, and may potentially be associated with higher levels of inflammation. In support, our group also found that kynurenine increases dramatically in runners participating in the 171-kilometre (106 mi) Ultra-Trail du Mont-Blanc. Furthermore, we also identified that kynurenine is a strong marker of COVID-19 severity.
The relationship between metabolites and health outcomes reinforces the important role that metabolism plays in the body. Gaining a better understanding of what a healthy metabolism looks like could provide unique insight into how it goes haywire when someone becomes ill and could offer new approaches to medical treatment.
