Need to Know #3: macronutrients


As we discussed in the previous article on essential nutrition basics, all food is comprised of three main components: calories, macronutrients and micronutrients. Macronutrients are the groups of larger nutrients that the body needs significant amounts of to meet its various requirements.

There are three macronutrients your body needs all with different calorie contents per gram: carbohydrate, protein and fat. Each macronutrient triggers a slightly different hormonal responses in your body with implications for how the energy from that nutrient is used. Carbohydrate, protein and fat are all essential for survival and these are the three we address today. Alcohol is also a macronutrient but it is a bit different class, because it isn’t essential (well at least not technically).

Need to Know #4: Carbohydrate


4 calories/ 17kj per gram

All carbohydrates are made up of sugars (saccharides). These range from simple sugars that are very sweet like in table sugar or fruit to complex carbohydrates, which include fibres and starches.

Monosaccharides (mono meaning one) are the most simple sugars being just a single molecule. They are water-soluble.

Glucose, fructose and galactose are monosaccharides. Things that are made up of these single sugar molecules tend to be sweeter. As fruit ripens the sugar molecules are broken down into monosaccharides, which is why they become sweeter with age. Similarly if you bake a whole sweet potato, a very sweet sticky sap like substance will begin to ooze out of it as the larger molecules are broken down into monosaccharides.

Disaccharides (di meaning two) are pairs of sugar molecules. Lactose (in dairy), sucrose (table sugar) and maltose are disaccharides. These sugars are easily broken apart by your body and don’t take long to be digested.

Polysaccharides are longer chains of sugar molecules strung together and are usually fibre rich. As they are longer chains they tend to taste less sweet and the presence of fibre means that they take longer to be digested. Most vegetables are made up of polysaccharides and contain lots of fibre, which is great for feeding the bacteria in your gut and for helping you feel satisfied for longer.

Polysaccharides found in refined foods like white bread and carbohydrate are not accompanied by fibre and therefore are broken down very quickly. The sugars from these foods enter your system as fast as something sweet like table sugar. This is why limiting your consumption of these kinds of foods is a good idea.

sugar structures

All food that is not fat or protein is carbohydrate. That means spinach and carrots are carbohydrates. Despite the fact that a bag of jellies and a bowl of spinach are made of largely the same macronutrient, it is the presence of micronutrients that make the difference in your body! We look at this in the next article.

All carbohydrates raise your blood sugar and promote an insulin response in your body. This is why despite the fact that carbohydrates have fewer calories per gram they should not be your only source of fuel. Most vegetables (except starches) tend to be fairly low in carbohydrates and high in micronutrients, so if this is where you get your carbs there is no need to be scared of them.

Carbohydrates that come from sweets, refined foods such as bread and pasta and even so-called “healthy” wholegrains (read why they’re not here) don’t tend to be the best for your body. However, we do not need to avoid this entire macronutrient. As the pendulum swung away from fearing saturated fat, it went very much in the direction of demonising carbohydrate. The rising popularity of low-carb diets for weight loss has caused many people (myself included for a while) to be terrified of carbs. You hear about people being so paranoid about their carb intake that they won’t even eat carrots and they worry about their consumption of carbs, even from great sources like sweet potato. While carbohydrates from processed foods aren’t great, we really do need carbohydrate to maintain good health. This is especially true for younger women and anyone that is active.

Carbohydrates are essential for the following functions:

  • A healthy thyroid, which regulates ALL your hormones including your reproductive and sex hormones;
  • fertility and pregnancy;
  • good quality sleep;
  • a strong immune system;
  • healthy digestion – the bacteria in your gut require good quality starches to keep you well;
  • keeping cravings at bay; and
  • energy, particularly if you are active.

The list could go on, but the point is most of us do need some carbohydrates. After all, glucose is our body’s preferred energy source.(1) While ketogenic and low carbohydrate diets have been shown to be very beneficial for some, they are not for everyone. We want to be looking at quality over quantity here. If all your carbohydrates are coming from whole foods (sweet potato, parsnip, white potato and fruits) then you don’t need to worry about consuming too much. While I wouldn’t encourage you to go crazy on fruit a couple of pieces a day is certainly not something to be afraid of!


Need to Know #4: protein


4 calories/ 17kj per gram 

Protein is the macronutrient that is arguably surrounded by the least controversy, although many people who get involved in gyms and bodybuilding do try to consume huge amounts of protein in the form of shakes and supplements. I would always advocate trying to get protein from whole food sources.

In the science and research communities there is certainly some debate around whether too much protein can have a deleterious effect on the body, but seeing as it is hard to overeat on real food sources of protein I would suggest if your protein comes from nature you will be ok. 

Protein is found in meat, poultry and fish as well as in diary products, nuts and legumes. Many starchy foods also contain small amounts of proteins. Protein is made up of amino acids, which are broken down by our body. Essential amino acids are those that we must get from food, because our body cannot manufacture them. All of these are found in various animal products, but not plant sources. This is why people who follow vegetarian and vegan diets often need to supplement. Nonessential amino acids are those that our body can make.

Diana Rodgers of Sustainable Dish does a great job of summarising the difference between protein on an animal foods vs vegetarian diet in this article.

Animal foods are the most complete protein sources that we have been eating forever!


The amino acids we get from protein are essential for:

  • Good immune function;
  • Tissue growth and repair;
  • Production of hormones and enzymes;
  • Maintenance of lean muscle;
  • Keeping you feeling satiated.


While our body will opt for carbohydrate as it primary source of fuel, we can also use protein when the carbs run out. Our bodies can convert protein to glucose by a process called gluconeogenesis.

If you are not a vegetarian for ethical or religious reasons aim to get protein from animal sources such as meat, poultry, fish, eggs and good quality dairy, if you can tolerate it. As I said, these are the most complete forms of protein and you will get a host of beneficial vitamins and minerals along with it.


Need to Know #6: Fat


9 calories/ 37kj

Fat contains the most calories per gram out of the macronutrients. This is part of the reason low-fat diets were held up as the key to weight loss for such a long time. However as I discussed in the previous article, weight control is far more complicated than a simple calories in = calories out situation. Of course this does play a minor role, but fat produces a very different hormonal response to other macronutirents, which is why it can actually help with weight management.

I cover fat in great detail in a number of other articles so I won’t spend much time on it here. As emphasised many times on the blog, you don’t need to be scared of eating fat. This is particularly true for saturated fats from animal products that our governments still want us to avoid. There is a huge amount of industry influence and politics at play here so the best thing you can do is just look after yourself by choosing foods that humans have always eaten – mainly animals and vegetables. Fat is the building block of our cells and essential for good health. When consumed in whole food form it is a wonderful and very nutritious part of your diet.

Need to Know #7: Alcohol


7 calories/ 29kj

Unlike the other macronutrients alcohol is not essential for human survival so we will not look at it in detail in this article. However, you should be aware that calories from alcohol still definitely count! The human body doesn’t fully metabolise alcohol, rather it burns and excretes it to get rid of a toxic substance from your system. This places huge strain on the liver, kidneys and the body’s other detoxification pathways. (2) This alcohol excretion process needs to occur first, before the body can deal with calories from any other macronutrient group. Therefore alcohol consumption does significantly impair weight loss and general vitality. It can bring a lot of joy and is a great social activity, so I will never tell you that you must give up alcohol completely. However, let’s not kid ourselves about the impacts of alcohol.

Coming next time: Micronutrients

That’s it for today’s macronutrient discussion. In the next article we will look at micronutrients and why they are an essential part of your diet.



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