When people talk about metabolism, they often imagine it as a single thing. Someone might say they have a "fast metabolism" or a "slow metabolism", as if metabolism were a single dial that can simply be turned up or down.
Physiologists tend to see things differently.
Metabolism is not one process. It is the sum of thousands of chemical reactions occurring every second in every tissue of the body. Some of those reactions store energy, others release it. Some build new molecules, others break them down. Together, they determine how we use the food we eat.
This brings us back to MCTs. One of the most common criticisms of MCT oil is perfectly reasonable: "It's still fat, how could it possibly be different?". After all, fat contains around nine calories per gram. Whether those calories come from butter, olive oil, or MCT oil, the energy content appears similar.
Yet, biology is rarely that simple.
One of the most important lessons I have learned throughout my career is that the body often cares as much about where a nutrient goes as it does about how much energy it contains.
Most dietary fats follow a relatively long journey after a meal. They are packaged into large particles called chylomicrons, travel through the lymphatic system, enter the bloodstream, and are eventually delivered to tissues around the body where they may be used or stored. MCTs behave differently. Because of their shorter chain length, they can be absorbed more rapidly and are transported directly to the liver through the portal vein. In many ways, they behave more like carbohydrates than traditional dietary fats.
This difference in transport may sound like a small detail, but in physiology small details often matter. Once they reach the liver, MCTs are rapidly oxidised and can be used as an energy source. Under some circumstances, they can also contribute to the production of ketone bodies. This unusual metabolic route is one reason why researchers became interested in MCTs long before they appeared in health-food shops and social media posts. Importantly, this does not mean MCTs are magic. One of the problems with nutrition is that every interesting biological observation eventually becomes a marketing claim. A genuine physiological difference becomes the "miracle fat" that melts away body fat.
That is not what the science says.
What the science does suggest is that MCTs may influence how the body handles energy, how hungry we feel, and how different tissues respond to nutrients. The magnitude of those effects, however, is often much smaller than the headlines would have you believe. This is one reason why I became interested in MCTs in the first place. When a friend first told me about MCT oil several years ago, I was deeply sceptical. Like many scientists, I suspected that the claims were too good to be true. Yet the more I read, the more I realised there was an interesting physiological question hiding beneath the marketing.
Why does the body treat MCTs differently from other fats?
That question eventually led to student projects in my laboratory and continues to shape some of the research we are pursuing today. And as often happens in science, answering one question only creates several more. For example, are all MCTs the same? If you search online for MCT oil, you will quickly discover products marketed as "pure MCT oil". On closer inspection, many of these contain predominantly octanoic acid (C8), one specific type of MCT. Others contain mixtures of C8, decanoic acid (C10), and lauric acid (C12).Whether these different MCTs have identical effects on metabolism remains an active area of research and is a topic we will explore in a future post. Because once again, physiology reminds us that the details matter.
Final thoughts
The most interesting thing about MCTs is not that they contain calories. The most interesting thing is how the body handles those calories. Understanding metabolism is not about finding miracle foods or quick fixes. It is about understanding the biological mechanisms that determine how nutrients are absorbed, processed, stored, and used.
MCTs provide a fascinating example of how small differences in biochemistry can lead to surprisingly different physiological outcomes. And for a scientist, that is often where the real story begins.