What are macronutrients?

Macronutrients are simply nutrients that are required in large amounts in the diet (as opposed to micronutrients, which are required in small amounts). For the purpose of this guide, we will use the widespread use of ‘macronutrients’, which is anything from which the body gets Calories.

Calories can be obtained from four different broad macronutrient categories:

  • Carbohydrates
  • Proteins
  • Fats
  • Alcohol

I will explain the basics of these categories below (with more detail to follow in subsequent guide parts):


Carbohydrates can be broken down into several subcategories:

  • Sugars (made of 1-2 sugar units bonded together): These are the simplest carbohydrates. They are composed of monosaccharides, disaccharides and polyols. All of these contain ~4kcal per gram.
  • Oligosaccharides (made of 3-9 sugar units bonded together): These are composed of malto-oligosaccharides (such as maltodextrin), and other oligosaccharides (such as raffinose). Most of these contain ~4kcal per gram, but certain forms (ie isomalto-oligosaccharide) contain only ~2kcal per gram. This is because some of the bonds in these molecules are difficult or even impossible for the body to break down, so we do not derive Calories from the whole molecule. These molecules are very high in fibre content.
  • Polysaccharides (made up of 10+ sugar units bonded together): These are composed of starches, as well as non-starch polysaccharides such as cellulose. Most of these contain 4kcal per gram, but like certain oligosaccharides, some starches and other polysaccharides are digestion-resistant, allowing us to absorb only ~2kcal per gram (this is generally soluble fibre), whilst some polysaccharides can not be digested at all, and as such are essentially Calorie-free (this is generally insoluble fibre).

Of note when working out macronutrient ratios is the fact that in the US, the ‘total carbohydrate’ value includes all carbohydrates including fibre, whilst in the EU (and I believe other places), the ‘carbohydrate’ value does not include fibre (which is instead listed separately).


Proteins can be very complicated molecules, but are always composed of various amino acids in a sequence. Due to the number of different amino acids and the length of sequences they can be combined in, there are thousands of different proteins that exist. However, luckily all of these contain ~4kcal per gram.


There are many different categories of fat, and we will deal with these in a lot more detail later in the guide. What category a fat falls into depends on both its chain length and the type of bonds in that chain. However, all fats contain ~9kcal per gram.


The final macronutrient – and one that many people forget to take account of when trying to lose weight, sabotaging their efforts – is alcohol. There are many different types of alcohol, but the one humans can consume safely (in moderation) is ethanol. Ethanol is found in all alcoholic drinks, and is what is referred to when the alcohol content of a drink is mentioned on the label. Ethanol contains 7kcal per gram, and to make matters worse, alcoholic drinks are often combined with other ingredients that contribute to the total Calorie count (most commonly sugars).

I won’t be going into any more detail in this guide about alcohol, but for those aiming to lose weight, it is vital to take alcohol into account. A single pint of beer contains 208kcal, and a single shot of vodka contains 97kcal. Additionally, as alcohol is treated as a toxin by the body, it is filtered out before anything else, so you won’t burn any fat until all of the Calories you have consumed from alcohol have been burnt.

What is a macronutrient ratio?

Now we have defined what the macronutrients are, and how many Calories are contained within them, we can work out a macronutrient ratio. A macronutrient ratio is simply the ratio of Calories you obtain from carbohydrates : protein : fat : fibre (with fibre sometimes being included in the carbohydrate component).

To work out a hypothetical macronutrient ratio then, we multiply each component (in grams) by the number of Calories in that specific macronutrient, and divide by the total Calories. As an example of this, below is a worked example of the macronutrient ratio of Soylent 2.0 (the nutritional information of which you can find here: http://files.soylent.com/pdf/soylent-drink-nutrition-facts-en.pdf).


We can see from the nutritional label that for every 400kcal serving, Soylent 2.0 contains 36 grams of total carbohydrates. This is composed of 9 grams of sugars and 3 grams of fibre (1 gram soluble, and as such 2 grams insoluble), as well as an unspecified amount of starch. However, because we know the sugar and fibre content, we can subtract these from the total 36 grams to get a starch content of 24 grams per 400kcal serving. Therefore we have the following contributions to the Calorie total:

  • 9 grams of sugar at 4kcal per gram = 36kcal
  • 1 gram of soluble fibre at 2kcal per gram = 2kcal
  • 2 grams of insoluble fibre at 0kcal per gram = 0kcal
  • 24 grams of starch at 4kcal per gram = 96kcal

This adds up to a total of 134kcal. We then divide that by the 400kcal serving size and convert to a percentage to find out that Soylent 2.0 is 33.5% carbohydrate.

If we were counting fibre separately, instead we would get values of 33% carbohydrate and 0.5% fibre.


We can see from the nutritional label that for every 400kcal serving, Soylent 2.0 contains 20 grams of protein. We can multiply this by 4kcal per gram to see that the protein in one serving of Soylent 2.0 contributes 80kcal. Dividing this by our serving size and converting to a percentage tells us that Soylent 2.0 is 20% protein.


We can see from the nutritional label that for every 400kcal serving, Soylent 2.0 contains 21 grams of total fat. We can multiply this by 9kcal per gram to see that the fat in one serving of Soylent 2.0 contributes 189kcal. Dividing this by our serving size and converting to a percentage tells us that Soylent 2.0 is 47.25% fat.

Soylent 2.0’s macronutrient ratio:

Now some of you may have noticed that the sum total of these macronutrients is 100.75%, not 100%. Simply put, this is because there is some rounding involved in nutritional labels and some very slight variance in the kcal/g of the macronutrients (but such a small amount of variance it is pretty much negligible). This is a small enough variance to not worry about, but for those who want a ratio that adds up to 100% for whatever reason, you can multiply by 100/100.75 (for Soylent 2.0). This may not be exactly accurate, but the difference is small enough it doesn’t really matter, and as it’s only a matter of personal preference, there are no consequences of doing so.

Using this calculation gives a macronutrient ratio in Soylent 2.0 of:

32.75% carbohydrates : 19.85% protein : 46.90% fat : 0.50% fibre.

What is the value of calculating a macronutrient ratio?

Typically, the average person will not have much of a reason to calculate a macronutrient ratio, though they may prefer to. However, for those looking to either lose fat or gain muscle, they can be helpful.

Fat loss:

Someone trying to lose fat may determine that they want to try a ketogenic diet. A ketogenic diet is a diet that restricts carbohydrates to a very small percentage of Caloric intake – typically ~5-10% – whilst having a moderate protein intake – typically ~15% – and a high fat intake – typically ~75-80%. This type of diet causes the body to use ketones – byproducts of fat burning – as its primary energy source, instead of glucose (sugar) which is most people’s default due to high-carb diets.

Different people have different sensitivities to carbohydrates, and as such can consume more or less without impacting their ability to be in ketosis. However, the general recommendation for someone trying keto for the first time is to stick to a maximum of 30 grams (some say 20 grams) of net carbohydrates (total carbohydrates minus fibre), and consume adequate but not excessive protein (with fat composing the rest of their intake). This is one of the situations where ensuring you’re meeting a specific macronutrient ratio can be very helpful, because too many carbohydrates or even protein can prevent you from being in ketosis, whilst too low a fat intake can lead to you feeling very hungry and increase the chances of binging on non-ketogenic foods.

Even if not wanting to follow a fully ketogenic diet, paying attention to your carbohydrate intake can be beneficial, as lower intakes (especially of low GI carbs) will allow your body to become more sensitive to insulin. Insulin resistance is a huge risk factor in obesity and diabetes.

Muscle gain:

People wanting to gain muscle may also wish to pay attention to their macronutrient ratios. Generally when people aim to put on muscle, they also want to minimise the amount of fat they gain at the same time. There is more debate regarding the best ratio for this, but the advice is generally to stick between 40% carbohydrates : 30% protein : 30% fat and 45% carbohydrates : 35% protein : 20% fat.

These ratios are mainly designed to ensure that you have enough protein intake for actual muscle building, enough fat for the increased hormone production required for workouts (eg testosterone) and enough carbohydrates to both maintain energy levels and deliver protein (and creatine for those that use it) to the muscles quickly. The carbohydrates used for energy level maintenance are generally low GI (such as ground oats) whilst the ones used for protein and supplement delivery are generally high GI (such as dextrose or maltodextrin) for quick absorption.

Naturally you’ll also need to pay attention to Caloric intake as well as macronutrient ratio in order to achieve your goals, but macronutrient ratios can play their part.

Part 2 – Calories and TDEE                                                                             Part 4 – Carbohydrates Overview