Proteins, Carbs, & Fats – Oh My!

Today we’re going to take it back to Nutrition 101, or Personal Health, or Basic Things Everyone Should Know, and talk about macronutrients.

What is a nutrient?

Nutrients are chemicals an organism needs in order to live and grow.  They are the fuel and structural building blocks for life.  “Essential” nutrients must be taken in from the environment (mostly from food), while “inessential” nutrients can be produced in the body (although they are often consumed in food as well).

Nutrients are broadly divided into Macronutrients – the ones you need a lot of – and Micronutrients – the ones you need smaller quantities of.  Although these categories are sometimes argued, for the purpose of this post, I will define the macronutrients as fats, proteins, and carbohydrates and the micronutrients as vitamins, minerals, and assorted others.  I’m leaving out water and oxygen, because they aren’t really relevant to the dietary discussion.

The Macronutrients

As I mentioned above, macronutrients are needed by the body in large amounts.  The reason for this is simple: they are the body’s fuel and major building blocks.  All of the energy you get from food (you know, calories) comes from the macronutrients.  That’s right, all of the fuel/energy for your body comes from these 3 substances.

Let’s break each of them down.


Chemically, carbohydrate molecules have one major purpose in the body: fuel.  They are easy to break down, providing energy to power cellular processes.  Every gram of carbohydrate provides about 4 calories of energy.  That said, carbohydrates are the only macronutrient that is inessential.  The body can obtain all of its energy from proteins and fats.  The body stores some energy in the form of a carbohydrate, glycogen, which is a primary fuel source during prolonged endurance exercise.  Simple carbohydrates are also sometimes just referred to as “sugars.”

Carbohydrates are the fastest digesting macronutrient and the fastest burning fuel source for the body.  As a result, carbohydrate consumption elevates insulin levels to a greater degree than any other nutrient.  The more “complex” the carb, the slower it digests and the lower the insulin spike it provokes.

From a fitness perspective, ideal carbohydrate intake depends vastly on goals and individual tolerance.  High-level endurance athletes (competitive distance runners, cyclists, triathletes, etc) should consume somewhat higher levels of carbohydrates to ensure adequate glycogen levels for exercise.  Non-competitive and non-endurance athletes should consume considerably fewer carbohydrates.  People looking to reduce body fat should consume the lowest levels of carbs and pay the closest attention to timing their carbohydrates appropriately.

Carbohydrates are found in vegetables, beans, fruits, sweet potatoes, pasta, bread, potatoes, rice, sweets, soda, table sugar, etc.  (listed roughly from most complex to less complex)


Proteins serve many purposes in the body.  They make up most of the active components of cells (the parts that actually do stuff) including the contractile structures that allow your muscles to move your body and the “power plants” in every cell that break down fuels for energy.  They can also be broken down and burned for fuel, providing about 4 calories per gram (just like carbs).  Proteins are essential nutrients – humans must consume them in order to survive because we cannot synthesize all of their component parts internally.  Proteins are often referred to as “the building blocks of muscle,” although they are also the building blocks for many other structures in the body.

Protein comes in faster digesting and slower digesting versions, and causes less of an insulin spike than carbohydrates.

From a dietary standpoint, I usually recommend 1 gram of protein per pound of body weight as a starting point for everyone.  Athletes and those people who strength train regularly may have higher requirements due to the muscle breakdown caused by exercise.

Major sources of protein include meat, fish, poultry, eggs, beans, nuts, and dairy.


Fats are arguably the most misunderstood macronutrient.  Fats are most commonly known as an energy storage mechanism for the body, as well as a fuel source, providing 9 calories of energy per gram.  Fats also make up the membranes of cells and are critical to many processes in the body.  Additionally, many vitamins are fat-soluble and require dietary fat to be metabolized properly.  Fats are an essential nutrient, which you must consume fats in food in order to survive.

Fats tends to be slow digesting, and cause very little, if any insulin response.  Making them, in some ways, the least “fattening” macronutrient…  (OK, OK – you can get fat eating too much fat, just like anything else)

Dietary fats come in many varieties including saturated, monounsaturated, and polyunsaturated.  Healthy consumption requires a balance of these types.

Most foods contain a blend of the types, in varying proportions.  High proportions of saturated fats are found in meat, dairy, and coconut oil, among others.  Monounsaturated fats are found in olive oil, canola oil, avocados, and nuts.  Polyunsaturated fats are found in many vegetable oils and fatty fish.

Wrap It Up Already

I know it was a little less practically applicable than normal, but I hope this overview has shed some light on the macronutrients.  For practical guidelines for getting the right types and proportions of each nutrient in your diet, check out these nutritional habits.