Demystifying Macronutrients

Macronutrients are one of the most divisive topics in nutrition…possibly the most divisive. Low carb, low fat, atkins, and keto for example are all diets based on a macronutrient paradigm. Let’s try to demystify what’s going on here.

The three macronutrients are carbohydrates, fat (fatty acids), and protein (amino acids). They are all made up of carbon, hydrogen, and oxygen in different combinations and protein also has nitrogen.

There are no “essential” carbohydrates, but there are essential fatty acids and essential amino acids. “Essential” just means that we need to get it from our diet because our bodies can’t make it. People typically don’t become “deficient” in carbohydrates because our livers can make glucose through gluconeogenesis but many people feel best when including carbohydrates in their diet because going too low carb for too long can presumably affect our hormones.

One of the macronutrients is not like the others in an important way. While carbohydrates and fatty acids are used primarily for energy, protein is primary used as a building block for lean body mass as well as repair in the body. It is used for energy only in the rare case that you’re not getting enough energy from fat or carbs.

This means that high protein is NOT likely to cause fat accumulation while high carbs and high fat are more likely to cause fat accumulation. Typically in a high carb/high fat meal, the carbs will be used for energy and stored as glycogen in the liver while the fat gets stored as body fat. This is where the divisiveness comes from: Is it fat or is it carbs that causes fat gain and metabolic syndrome?

The truth is probably that they both can contribute to fat gain and metabolic syndrome, especially in high amounts (like when processed) and especially when consumed in high amounts together. This is why many people prefer to either do low carb OR low fat. Either way, you’re limiting the ENERGY consumed, which has metabolic benefits and allows you to start tapping into your fat stores to use some of that previously-stored energy.

The Plant-Based (Vegan) vs. Animal-Based (Carnivore) debate gets thrown under this macronutrient umbrella as well because plants typically contain higher amounts of carbohydrates and lower amounts of fat while animal foods contain almost no carbohydrates and a lot more fat. Both plant foods and animal foods contain protein, though there is a lot of debate about the bioavailability of that protein in the human body. Many people believe plant protein is not as bioavailable or not as plentiful in plants as it is in animals, and some of the debate comes down to how much protein we actually need as human beings.

There is also some research that a low protein diet can have longevity benefits, but this is tricky. Low protein could mean loss of lean body mass including bone mass, which could have detrimental effects. Part of the reason low protein is seen as beneficial is because protein activates mTOR, which I’m not super versed on but is said to contribute to disease when activated too much. However, it’s also known that insulin activates mTOR, so many people who promote higher protein diets prefer to lower mTOR through intermittent fasting and reducing carbohydrates.

Overall, macronutrients are energy and building blocks. Consuming too much energy (carbs and fat, especially when processed) can cause metabolic issues as well as fat accumulation in the body, both as benign subcutaneous fat as well as inflammatory visceral fat. Consuming too much protein will cause some of that protein to turn into energy. Not consuming enough energy (carbs and/or fat), especially when you either don’t have fat on your body or your body can’t access your fat, can cause your body to go into starvation mode, which can lower metabolism and cause all sorts of hormonal issues. Not consuming enough protein can cause low energy, weakened lean body mass, and poor tissue repair in the body.

The important thing to remember is that most foods contain a mixture of all or some of these macronutrients with the exception of things like butter and oil, which are purely fat. When eating whole, unprocessed foods, you’re not likely to over-consume energy, but it’s very easy to over-consume energy when eating processed, packaged foods, candies, pastries, and anything that is dumped in oil before you eat it.

I hope this helps to demystify macronutrients so that you can make more informed decisions about how you’d like to eat based on your goals (if any) and what you like.