What On Earth Are Macronutrients? (And why you need to know)

What On Earth Are Macronutrients? (And why you need to know)

You've likely heard the word "macronutrients" or its colloquial and abbreviated term "macros" hundreds of times. It sounds fancy and complicated, but what does it actually mean?

What are Macronutrients?

A macronutrient is simply a chemical substance (such as protein) that is required in relatively large amounts to the growth and health of a living organism (1).

In the context of our diets, the three macronutrients are protein, fat, and carbohydrates, which are required in a certain amount for optimal functioning.

This article not only will explain what a macronutrient is but illustrate how each of them can assist you with your fitness goals.

Macronutrients for health/fitness, muscle growth, and weight loss.

Countless studies show that protein is what drives muscle growth and recovery (2), that's no secret! So whether you're lifting weights, playing tennis, or sprinting in the park, protein is a must.

what are macronutrients

But it's proteins' role in keeping you full that many people don't know about!

In comparison to the other macronutrients carbohydrates and fat, protein is superior when it comes to keeping you full (3). This makes it the best macronutrient to consume when you want to lose weight!

But it doesn't stop there: when you eat a gram of protein, you're eating 4 calories. You're also eating 4 calories when you eat a gram of carbohydrates, but eat a gram of fat, and you're consuming 9 calories! (4). That's more than double!

And the third reason protein is better than the other two macronutrients for weight loss, is because of the energy your body requires to break it down during digestion. To elaborate, we know:

Protein = 4 calories per gram. 

Carbohydrates = 4 calories per gram.

Fat = 9 calories per gram. 

Whilst it seems like protein and carbohydrates are tied in first place, it's not the case! Protein is in reality just under 4 calories because of the energy required by the body to break it down (5).

Specifically, you lose 20-30% of the calories from protein in the digestion process; so when you consume 100 calories from protein you're actually really consuming 70-80 calories (5).

For carbohydrates, that percentage is just 5-10%, and for fat, it's only 0-3% (5).

So let's go back to our table, and see the REAL caloric value of macronutrients:

Protein = more like 2.8 calories per gram (down from 4)

Carbohydrates = more like 3.6 calories per gram (down from 4)

Fat = more like 8.73 calories per gram (down from 9)

So you can see why protein is the winner here, and why most fat loss diets are encouraged to be high in protein.

How this relates to your goals

And whilst this knowledge is well and good, the difference between you succeeding with your fitness goals or not is knowing how much of each macronutrient to eat daily.

Whilst diving into how to calculate your macronutrients for your health and fitness goals is beyond the scope of this article, most diets are calculated so that you eat 500 calories less than your body burns daily (6). This ensures that fat is burnt.

what are macronutrientsSo say "Tina" is a 34-year-old female who burns 2100 calories a day (calculated by knowing her age, weight, and daily exercise routine). For an optimal fat loss diet, Tina would need to consume 1600 calories per day (a 500 calorie deficit).

This means that every day, Tina could eat:

Protein: 160 grams (640 calories)

Carbohydrates: 90 grams (360 calories)

Fat: 66 grams of fat (594 calories)

Total: 1594 calories

This means that Tina would order certain Workout Meals that she knew fitted within her macronutrient requirements for each day, and cook/purchase food that ensured she stayed within these parameters.

By looking at the labels of everything she ate, Tina would know if she was eating too much.

Now, if Tina eats more than her allocated macronutrients, she will reduce the size of her 500 calorie deficit, and thus not lose as much weight and get the progress she wants.

And this is why people fail on diets: they eat above their allocated number of macronutrients for too long, because they crave high-calorie foods and "splurge", or lose interest entirely.

With all this information in mind, you should now be able to make sense of the "macro" conversations you've heard over the years.

Real-world translations:

Fitness fanatic: "I'm not eating cake, it's too high in macros"

Translation: There's way too much fat and carbohydrates in that, and I'm trying to lose fat!

Fitness Fanatic: I can eat that donut, it fits my macros!

Translation: I can still eat that donut and be under the required amount of protein, fat, and carbohydrates I need to eat in a day. So, I won't gain weight!

Fitness Fanatic: "I love chicken breast, it's got great macros"

Translation: The protein will keep me full, and there are minimal fat and carbohydrates, so I'm not over-consuming calories.

Fitness fanatic: I'm on an IIFYM diet, I've lost 2 kilos!

Translation: IIFYM stands for "If It Fits Your Macros." It's a flexible approach to dieting that says you can eat a chocolate bar "if it fits" within your allocated daily amount of protein fat and carbohydrates, as no fat can possibly be gained.

I hope this article has allowed you to understand macronutrients much more, and that you're no longer confused by the "macro" talk around you.

In fact, we're hoping you may even be able to join and/or start the conversation!


(1) https://www.merriam-webster.com/dictionary/macronutrient

(2) Peter J. Garlick, The Role of Leucine in the Regulation of Protein Metabolism, The Journal of Nutrition, Volume 135, Issue 6, June 2005, Pages 1553S–1556S, https://doi.org/10.1093/jn/135.6.1553S.

(3) Soenen S, Westerterp-Plantenga MS. Proteins and satiety: implications for weight management. Curr Opin Clin Nutr Metab Care. 2008;11:747–751. doi: 10.1097/MCO.0b013e328311a8c4.

(4) National Research Council (US) Committee on Diet and Health. Diet and Health: Implications for Reducing Chronic Disease Risk. Washington (DC): National Academies Press (US); 1989. 6, Calories: Total Macronutrient Intake, Energy Expenditure, and Net Energy Stores. Available from: https://www.ncbi.nlm.nih.gov/books/NBK218769/

(5) van Baak MA. Meal-induced activation of the sympathetic nervous system and its cardiovascular and thermogenic effects in man. Physiol Behav. 2008;94:178–86.

(6) Carels RA, Young KM, Coit C, Clayton AM, Spencer A, Hobbs M. Can following the caloric restriction recommendations from the Dietary Guidelines for Americans help individuals lose weight? Eat Behav. 2008 Aug;9(3):328-35. doi: 10.1016/j.eatbeh.2007.12.003. Epub 2008 Jan 4. PMID: 18549992.

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