What are the Macronutrients?
Macronutrients – protein, fat and carbohydrate are our main dietary sources of energy. The three main macros make up the bulk of our daily diet. While carbs are not strictly essential, most healthy diets include good amount of all three macronutrients.
Energy in food is measured in calories. This is why it is important to actually count calories. Calories are not the enemy but simply a measure of energy consumption.
The only known way to maintain a healthy weight is to maintain calorie balance — consuming the same amount of calories as we use up. If we consume more than we use, then we will put on weight. On the other hand if we consume less than we use up, we will lose weight. It’s that simple.
How many calories are in a gram of protein, fat & carbohydrates?
Protein — 4 kcals / gram
Carbohydrates — 4 kcals / gram
Fat — 9 kcals / gram
To lose about 1lb (450 grams) of fat over a week, we need to use about 580 kcal more per day than we consume. For an average person (~160lbs or 73kg) that means 90 minutes of walking, 45 minutes of jogging or 55 minutes of swimming.
What exactly is a calorie?
Definition of a calorie: The unit used to describe the amount of energy in food. In scientific terms a calorie is the amount of energy required to raise the temperature of 1g of water from 14.5 to 15.5 degrees centigrade. Because this is quite a small amount of energy, we normally use kcals (1 kcal = 1,000 cal). We calculate the number of calories in a sample of food by burning it and seeing how much heat it gives off.
Why is protein important?
Protein is one of the essential macronutrients and key part of a balanced diet. It supplies not only energy, but amino acids, the molecules that join together to make protein. Amino acids are vital structural components of tissues like muscle and connective tissue.
Proteins are also required to make enzymes, hormones, neurotransmitters and receptors and transporters on cell membranes. There are 8 amino acids that we must eat. Those are known as essential amino acids — we are not able to produce them from food.
These are threonine, methionine, lysine, valine, leucine, isoleucine, phenylalanine and tryptophan. For infants, histidine is considered essential, too. Other amino acids found in the body, such as tyrosine or cysteine, can be synthesised from the essential amino acids which means they not ‘essential’ in the diet.
Good sources of protein
Animal sources of protein
Good dietary sources of protein include meat, fish and eggs. These food groups are called ‘complete’ or ‘first class’ proteins. They contain all the essential amino acids required to support body protein synthesis.
Vegetable sources of protein
Vegetables and cereals also contain protein in varying amounts, but mostly are ‘incomplete’. They have one or more essential amino acids missing or in too small an amount to support body tissue synthesis. These ‘limiting’ amino acids limit protein synthesis in the body. You can overcome this by mixing and matching vegetable source proteins.
Combining vegetable sources of protein to make complete proteins
Different vegetable foods have different amino acid profiles, so a combination can offset any given deficit.
For example, beans or bread alone are incomplete in terms of essential amino acids. Combining them together as ‘beans on toast’ solves the problem. It is easy to meet protein requirements on a vegetarian diet, as long as you consume variety of plant protein.
Beans, nuts, seeds and cereals all contain useful quantities of protein.
How much protein is needed?
The general rule is 0.8g of protein per kg of body weight per day. This is true for most adults leading an ‘average’ lifestyle. So, an average person weighting around 160lbs (73kg) requires 58g of protein per day to stay healthy.
When do we need more? This figure is higher during growth, especially adolescence; when exercising heavily/regularly (to support extra muscle growth); and in old age (to offset protein loss from ageing muscle). An increase up to 1.2 or 1.4 g per kg of body weight per day should cover most cases. This increase can be met through the diet alone or by adding protein supplement such as whey or pea protein. Protein normally makes up around 15-20% of our daily calorie intake from macronutrients.
Can you eat too much protein?
While protein is essential, like anything too much may be a problem. Excess protein, especially from animal sources, can potentially put a strain on the kidneys. This is because the kidneys need to excrete the waste products of protein metabolism. Interestingly, protein from vegetable sources seems to be less of a problem. The evidence shows that there is less risk of overdosing with protein from vegetable sources. Further, each gram of protein contains 4kcals. So eating too much protein can also lead to weight gain.
Are you getting enough protein from your diet?
Studies show that most people in developed countries meet their protein requirements through normal eating. However, protein in the diet is helpful for achieving satiety (knowing when we are full) and supports heavy exercise and training schedules, including endurance exercise. Some people therefore may benefit from protein supplements as they give known quantities of good quality protein without extra fat or excess sugars.
What is fat and how do we use it?
Fat includes oils (e.g.sunflower oil), solid fats (e.g. lard), and the fat in animal meats and fish. Fats are also part of the essential macronutrients.
Fatty acids are chains of carbon with hydrogen attached. These chains are joined together by a molecule called glycerol. Fatty acid chains can be burnt (oxidised) by the body as fuel to provide energy and the glycerol part of fat can be converted by the body into glucose when required.
Fat is essential as it contains the essential fatty acids:
Omega 6 linoleic acid
Omega 3 linolenic acid.
The essential fatty acids give rise to a vital group of molecules in the body called eicosanoids. Eicosanoids have a wide range of functions including:
Controlling immune responses
Balancing inflammation in the body
Signalling between cells
While many fats can be converted within the body (we can store excess calories eaten as sugar for example by converting it to a fat and storing it as body fat), the essential fatty acids must be eaten as the body cannot make them.
Dietary fats differ according to the number of carbons in the fatty acid chains and the number of hydrogen atoms bound to the carbons. According to these characteristics the fatty acids are given different names such as oleic acid (found in olive oil) or palmitic acid (found in meats and cheeses).
How much fat do we need?
We need less than 5% of our daily calories to be from the essential fatty acids to be healthy. Most people however actually eat around 30% or more of their daily calories as fat. This is mainly because fat makes things tasty, it carries flavor molecules and gives food a nice texture. There is evidence that we are ‘genetically programmed’ to like fatty foods too.
The recommendation for the ‘average person’ is not to eat more than 30% of daily calories from macronutrients as fat. So if you are eating 2,000 kcals per day, this would equal about 660kcals (around 5 tablespoons of vegetable oil.
There is some confusing terminology connected to fatty acids. Saturated and mono-unsaturated fats are the ones we consider “bad” and the poly-unsaturated we consider “good”. These terms refer to the amount of hydrogen attached to the carbon in the molecule.
If the maximum number of hydrogen atoms is bound to carbon the fatty acid is called a saturated fatty acid.
When there is at least one less hydrogen than required to make this process possible, it is called a mono-unsaturated fatty acid.
Finally, if two or more hydrogen atoms are missing this is called a polyunsaturated fatty acid (PUFA).
Most fat in the diet is a mix of saturates, mono-unsaturates and poly-unsaturates.
Typically, meat and dairy contain higher levels of saturates whereas plants and vegetables contain higher levels of mono and polyunsaturates.
Different types of fat do different things
All fats are a source of energy and are necessary component of well optimized diet that contains all macronutrients. A balanced, varied diet naturally provides the necessary supply the essential fatty acids. We can run into problems with fat in two main ways:
Fat leads to weight gain
Firstly, fat is the most energy dense macronutrient so eating too much can quickly lead to weight gain. This is the case even if we consume so called ‘good fats’. It is important to be aware of the high calorie content of fatty foods and limit their intake.
Having said that, studies indicate that people attempting very low fat diets may have issues with depression. You also need fat for the fat soluble vitamins: A, E, D & K. The minimum fat we need is at least 11g per day which is equivalent to 1 tablespoon of olive oil.
Too much bad fat can lead to inflammation
The second issue with fat relates to its ability to control inflammation. Taking too much Omega 6 linoleic acid (which is pro-inflammatory) relative to Omega 3 linoleic acid (which is anti-inflammatory) can lead to an overall low level systemic inflammation which is bad for our health.
Inflammation is the way the body deals with injury or infection and is vital for survival. Long term or excess inflammation however is unhealthy and even dangerous. One reason for excess inflammation is a high Omega 6 fatty acid intake relative to Omega 3 fatty acid intake. We can beneficially alter this balance by eating more Omega 3s.
Where can we get Omega 6 and Omega 3 from?
Omega 6 fats are dominant in commonly eaten oils such as sunflower and corn oil and can be hard to avoid. Omega 3 fats which are found in fish oil, krill and flaxseed are often less well represented in the diet. It’s important to try and ensure a good Omega 3 intake.
According to recent research we eat too much Omega 6. While there are Omega 3 fats in vegetables the conversion of this to anti-inflammatory molecules is not always efficient. Fish and other marine oil sources contain the key eicosanoids, eicosapentanoic and docosahexanoic acids.
Fat for vitamins
Finally, fats are the dietary source of the fat soluble vitamins, A, E, D and K and consuming fat is necessary to deliver these essential micronutrients. For more information on the sources and benefits of the various vitamins, please see our Vitamins & Minerals section.
We are born liking fatty foods because during evolution fat provided an excellent source of calories to help us survive. You need to be careful not to have too much fat as part of your macronutrients balance. It’s easier to put on weight faster since fat is very energy dense compared to protein and carbs.
How to balance your fat intake:
- Focus on eating good fats. If you eat fat focus on more olive oil, coconut oil, nuts, seeds and fruits / veg like avocados.
- Limit fat intake. Eat no more than 5 tablespoons of fat per day — that would include salad dressings, avocado on toast etc.
- Choose fish and lean meat. Have no more than 5 tablespoons of fat per day — that would include salad dressings, avodado on toast etc.
In a typical diet, carbohydrates make up the largest part of each meal (some 40-60% of daily calories on average). Carbs are the most affordable and plentiful macronutrients.
Carbohydrates provide energy and can be converted to non-essential storage fat in the body. While we need carbs to stay alert, energetic and healthy, not all carbs are made equal and we need to be picky.
Sugars such as glucose, fructose (fruit sugar) and galactose (milk sugar). Table sugar (sucrose) is actually a molecule of glucose attached to a molecule of fructose.
Foods such as potatoes, rice, cereals (wheat, oats, maize etc).*
Fibre is a form of carbohydrate which is not broken down in the gut. It originates from plant cell walls and is essential for a well functioning digestive system.*
* Starches and fibre make up what’s known as complex carbs
For the average person, the largest dietary intake of carbohydrates is via starches, bread, potatoes, pasta and rice. These foods are made of the sugar glucose in long chains which makes up starch. When we eat starchy foods we are essentially eating glucose. Once digested all starches become glucose.
Did you know? – Glycemic Index
The Glycemic Index (GI) of a carbohydrate food refers to the rise in blood glucose it produces when eaten. Some ‘complex’ carbohydrates such as white bread and potatoes actually have a higher GI than sugar. In general, the more ‘refined’ a carbohydrate is, the higher the GI will be.
Are carbs essential macronutrients?
While not strictly essential, carbohydrates are the most affordable source of energy and are found in foods such as fruits that contain vital vitamins and minerals. Fibre in fruit, vegetables and cereal products is low in calories and good for the gut and is also from carbohydrate foods (roughage).
While the body always requires a certain amount of the simple sugar, glucose in the bloodstream, this glucose can be made from protein or fat in the liver, hence we don’t really need to eat glucose or starch to maintain glucose in our blood.
However, this rate of conversion is relatively slow, so if we are active and require much glucose, eating carbohydrates is the easiest way to maintain blood glucose levels. This is especially true for people who exercise regularly. Athletes need to store glucose in their muscles (glycogen) to use as fuel during intense physical activity.
Athletes understand this and often ‘carbohydrate load’ to maximise the stored glycogen in their muscles.
Did you know? – Benefits of eating fibres
Fibre, (or scientifically, non-starch polysaccharides) is a form of carbohydrate that cannot be broken down in the human gut and/or be absorbed by the body. It may not provide us nutrients directly, but can help ‘friendly’ bacteria grow in our gut. Healthy amount of fibre also helps prevent constipation. Added benefits is that fibre make us feel full, without adding extra calories to our diet.
How to balance your carbs intake?
Fewer than 5 tea spoons
Try to minimise added sugar as much as possible. In general, do not exceed 10% of total daily calories as sugars (10% dietary energy for an average person equals about 200kcals). This doesn’t include ‘intrinsic sugars’ from fresh fruit.
Less than 200 grams
Limit the intake of starchy foods to no more than around 40% of total daily calories (40% of daily calories for an average person equals about 800kcals). In total around 50% of calories in macronutrients come from carbohydrates per day.
More than 5 portions/day
Focus on having at least 5 portions or more of fruit and vegetables to ensure a good fibre intake and good natural sources of minerals, vitamins and antioxidants.