June 15


Understanding Carbohydrates: a Beginner’s Guide

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These days, carbohydrates can be a controversial topic in the health and fitness industry. In one camp, we have the "carbs are bad" crew, and in the other we have "you need carbs." So what's the deal? Since individual carbohydrate needs aren't a one-size-fits all solution, I've put together this essential guide. Below, you'll find out how to improve your carbohydrate intake and base it on a level that works for you and your own nutrition needs. I'll cover things such as how to choose healthier carbohydrate options, how to eat carbs and still lose weight, as well as carbohydrates for sports and fitness performance.


Whether you're training for your first half-marathon, trying to lose weight or hitting the gym to bulk up, I'll explain everything you need to know about carbohydrates.

Let's start with the basics - what are carbohydrates?

At a molecular level, carbohydrates contain carbon, hydrogen and oxygen atoms. Generally, the hydrogen and oxygen atoms appear in a 2:1 ratio, similar to water (H20). Therefore, "carbohydrate" could be loosely translated to "carbon plus water".

Carbohydrates are present in a broad range of foods. From fruit, vegetables, grains, drinks, snacks, legumes and dairy. Therefore, we can't think of all carbohydrates being the same. Different carbohydrates might affect your body differently depending on their source.

In terms of energy, carbohydrates provide 4 calories per gram. Alternatively, if you like to think in terms of kilojoules, this is equivalent to 16.7kJ.

We can divide the types of carbohydrates found in food into two different categories - simple and complex. Generally speaking, most foods that contain carbohydrates will have a combination of both categories. This isn't always the case though, which we'll cover shortly.

What are Simple Carbohydrates?

Essentially, we can think of simple carbohydrates as "sugar."

Remember though, sugar is a general term and there are several different chemical compounds that all under the sugar umbrella.

A brief breakdown on sugar structure in simple carbohydrates

In their simplest form, there are 3 types of sugar molecule. We call these glucose, fructose and galactose. All 3 molecules have the same chemical formula, C6H12O6, but they have slightly different structures.

Effectively, these small molecules become the building blocks for other types of carbohydrates, and sugars.

For example, sucrose (ordinary table sugar) is one molecule of glucose and one molecule of glucose joined together. Lactose, found in milk, is one glucose connected to one galactose. If we joined 2 glucose molecules together, we'd get another sugar called maltose.

In general, sugar molecules are made up of only short chains of these individual blocks. As a result, they're relatively easy for you body to break down and quick to digest. Therefore they'll enter your bloodstream quickly after consuming them. Essentially, that's why foods high in simple carbohydrates taste sweet. Your tongue detects the sugar molecules being broken down almost instantly.

What sort of foods are high in simple carbohydrates?

By simple carbohydrates, we're essentially talking about sugars. They appear in a wide range of foods:

  • sweeteners (syrups, table sugar, honey)
  • lollies, sweets and candy
  • jellies, jams and spreads
  • refined (white) flour

It's important to remember though, that the following types of food also contain simple carbohydrates too:

  • fruit
  • vegetables
  • beans and legumes
  • dairy products

However, foods containing these natural sugars also contain many vitamins, minerals and important micronutrients. Not to mention dietary fibre, protein and other beneficial components.

And that's the important part to remember. Ideally, we want to look at the food as a whole in deciding whether it's healthy for us or not. It's not a simple matter of looking to see if it has sugar or not. Cakes, muffins, biscuits and pastries don't carry much in the way of nutrition, so the added sugar in them isn't going to do us much good either. On the other hand, foods with natural sugars AND additional micronutrients can and should form part of your daily healthy diet.

What are Complex Carbohydrates?

We've looked at simple carbohydrates and how they are short chains of sugar building blocks. In basic terms, complex carbohydrates are just longer chains.

Generally, complex carbohydrates contain 3 or more sugar molecules connected in a chain. Additionally, complex carbohydrate food sources also include fibre as well as protein and possibly healthy fats too. Not to mention vitamins, minerals, antioxidants, phytonutrients and other goodies.

Although complex carbohydrates use the exact same sugar building blocks found in simple carbohydrates, the chains are much longer. Therefore, they take a longer time for you body to breakdown. For this reason, complex carbohydrates don't taste as sweet.

These longer chains also slow the whole digestion process overall. Therefore, the sugar molecule building blocks aren't absorbed into your bloodstream as quickly. The net result is that your insulin response is more gradual, and you'll feel fuller for longer. This can be an important part in appetite management.

Some examples of foods rich in complex carbohydrates include:

  • bread
  • pasta
  • rice
  • beans
  • legumes
  • whole grains
  • vegetables

Is dietary fibre also a complex carbohydrate?

Yes, fibre is a carbohydrate made up of long chains of individual building blocks. However, dietary fibre doesn't add much in the way of calories to your diet as it isn't really broken down or absorbed in your body.

Why don't the carbohydrate values on nutrition labels add up?

In a lot of nutrition labels on food packaging you'll generally find:

  • dietary fibre, and
  • sugar

Both of these are often listed under Total Carbohydrate.

However, by 'total carbohydrate' we're actually meaning ALL the types of carbohydrates within the food. That is, sugar, dietary fibre and starch. Nutrition labels only list dietary fibre and sugar as that's all we tend to care about.

Can I work out how much starch is in a food from its nutrition label?

Yes. If you want to calculate how much starch is in a particular food, you have to do some simple maths.

The total carbohydrate includes sugar, fibre and starch. So to work out how much starch is present ,we'd use the formula:


What about net carbohydrates?

Some diet protocols, such as Keto and Atkins use the concept of net carbs in their approach.

The theory goes that net carbs are the amount of carbohydrates in your food that can affect your blood sugar levels. That is to say, the carbohydrates that your body absorbs into the bloodstream.

Essentially, any insoluble fibre you eat isn't digested or absorbed by your body and doesn't enter your bloodstream. Likewise, sugar alcohols are treated in much the same way.

For that reason, we can work out net carbohydrates using figures for total carbohydrates, dietary fibre and sugar alcohols.


However, we must remember that "net carbs" isn't an officially defined term within the scientific community. Therefore many regulatory bodies don't acknowledge or include their information on food packaging.

Additionally, your body can at least partially digest some types of dietary fibre and sugar alcohols. Manufacturers often use some of these types in processed "diet" foods, bars and supplements to lower their net carbohydrate figure. However, even though their levels aren't included in the carbohydrates listed on the packaging, you still may be absorbing at least some of their sugar content.

Outside of the United States, many countries don't count sugar alcohols or dietary fibre in their carbohydrate figures on nutrition labels. You could argue then that they are already displaying "net carbohydrates" by default.

If you're tracking net carbohydrates as part of a blood sugar management strategy, it's important to check with your doctor first.

How to choose the right types of carbohydrates in your diet

Firstly, when deciding which carbohydrates to eat and drink, it make sense to choose nutrient dense sources. That is, foods that contain many vitamins, minerals and other beneficial nutrients in addition to the carbohydrates.

Here are 3 simple rules to help you choose the best carbohydrate options:

  1. 1
    Eat more complex carbohydrates from whole foods as close to their natural state as possible
  2. 2
    Eat fewer refined sources of complex carbohydrates
  3. 3
    Limit your intake of simple carbohydrates.

In practical terms, this would pan out as below:

  • Include lots of vegetables, beans, pulses, nuts and seeds in your daily diet.
  • Additionally, eat wholegrain bread, pasta and brown rice where possible instead of their more refined counterparts
  • Avoid junk food except on occasion to help reduce the number of "empty calories" you consume.
  • Include fruit and dairy regularly in your diet since they contain many additional nutrients, vitamins and minerals.

A notable exception for highly active people and their carbohydrate intake

If you're a highly active person, athlete or train hard regularly and you're looking to improve your performance, not all of the above riles will apply.

How much carbohydrates should I eat each day? Working out your carb intake target

Glucose, one of those simple sugar building blocks, is the preferred fuel source for your body's muscles and organs. In fact, our red blood cells can ONLY use glucose as fuel to power their intracellular metabolism.

As a general rule, our body must supply a constant stream of glucose to our brain. Many processes within our physiology are hardwired to prioritise the brain getting fuel over anything else.

In a nutshell, if we don't eat enough carbohydrates, our body breaks down protein to create glucose. This protein comes from our muscles and organs.

In Australia, we don't have a Recommended Daily Intake (RDI), Estimated Average Requirement (EAR) or Adequate Intake (AI) for carbohydrates. Now this in no way suggests they aren't an important part of our diet. They almost certainly are. It's just we can't have a determined 'minimum' target for the population to consume.

Essentially, if we don't eat enough carbs, our body will make them for us. However, it will use our hard-earned protein stores to do this. This can be both metabolically and economically expensive.

What we do know though is that, in Australia, the 'Acceptable Macronutrient Distribution Range' for carbohydrates is 45-60% of dietary intake. That means, around half of the calories we consume should be in the form of carbohydrates.

Do different people need different amounts of carbohydrates in their diet?


Active people, who exercise regularly should definitely consume more carbohydrates than sedentary individuals. Carbohydrate offers prime muscle fuel and provides energy for grueling gym sessions, competitive sport and muscle building.

Therefore, if you're on the more sedentary side, you should tailor your carbohydrate intake towards the lower end of the scale. That is, aim to consume 45% of your daily calories as carbohydrate. Conversely, if you're a regular exerciser, your carbohydrate intake target will be closer to the 60%-mark.

Like many aspects of nutrition, a bit of trial and error is involved. Experiment with your carbohydrate intake and overall macro balance to find what works best for you.

How to work out how many grams of carbohydrate you need in a day

Firstly, you need to decide what percentage of your daily intake should come from carbohydrates. Then, convert that percentage to a decimal. For example, 50% represents 0.5, 60% is 0.6, etc.

Now multiply this by your estimated energy intake target. This will give you the number of calories you should consume from carbohydrates.

To convert this number of calories to grams of carbohydrate, divide by 4.

Should I go low carb? Here's what to know about going on a low carbohydrate diet

In general terms, a "low-carb" diet provides less than 40% of your calorie intake from carbohydrate. The truth is, many people have lost large amounts of weight, and kept it off, using this dietary approach. However, it's not for everyone.

There's a reason it's popular. People have had good results with it. However, it's certainly not the only way to lose weight, and their can be some drawbacks to going low-carb.

Potential side-effects of a low carbohydrate diet

As a general rule, I like to recommend that my clients avoid cutting out macronutrients or food groups. Going on an extremely restrictive diet can cause more problems than it solves in many people.

However, if you do choose this approach and decide to drastically reduce your carbohydrate intake, you should know that it will certainly have an effect of your blood sugar levels.

In some people, low blood sugar may cause:

  • shakiness
  • anxiety or nervousness
  • chills
  • increased irritability
  • becoming lightheaded
  • dizziness
  • headaches
  • hunger
  • nausea
  • tiredness
  • fatigue
  • impaired coordination
  • feelings of discomfort

These effects, combined with the restrictive nature of the diet, can make it difficult to sustain.

7 factors to consider when switching to a low-carb lifestyle

What if at this point you still decide you want to give eating fewer carbs a go? Well, I've got you covered. Here's some advice for a sustainable transition to a lower carbohydrate diet.

Beware of blood sugar lows

Reactions to low blood sugar vary from person to person. When first starting out on a low-carb approach, monitor yourself for signs and symptoms of low blood sugar.

If you find yourself experiencing these, perhaps you need a little more carbohydrates to get you through. Eat a small serving of a carbohydrate-rich food source. For example, a slice of bread, piece of fruit or some crackers

Ease yourself into a low-carb lifestyle gradually

Take your time and allow your body to adjust a new lower carbohydrate eating approach. You might like to use a food tracking app, such as MyFitnessPal to log your food intake for at least a week. This will give you a good understanding of how many grams of carbohydrates you consume each day.

Then, slowly decrease your carbohydrate intake target by around 5-10% each week. That way, you give your body the time it needs to adjust without too much stress.

Remember, that by decreasing the proportion of carbohydrate in your diet, you'll need to increase either your protein or fat intake, or both. This will help offset the reduction in your energy intake.

You might like to consider tracking 'net carbs' rather than just carbohydrates

Some dietitians believe tracking net carbs allows greater flexibility with your food choices. Additionally, it allows you to hit your dietary fibre intake recommendations without going over your carb intake target.

Some people might find that tracking net carbohydrates also helps keep their blood sugar levels in check too.

Some food tracking apps allow you the option to track total net carbs, either in each food, meal or day.

Prioritise nutrient-dense, balanced food choices in your daily diet

If you're on a low carbohydrate diet, every carb counts! Therefore, choose the high-quality carbohydrates to maximise your intake of micronutrients.

Choose wholegrains, fruits and vegetables.

Likewise, keep your protein choices healthy and balanced too. Opt for eggs, legumes, chicken, tofu and leaner cuts of beef and pork.

In terms of healthy fats, be sure to include fish, nuts, olive oil and avocado. That way, you'll be getting the necessary monounsaturated and polyunsaturated fats.

Keep up with your water intake

Remember to keep an eye on your hydration levels. It's likely that by cutting your carbohydrate intake, you'll consume more protein. As a result, you'll need plenty of water to help your body break down and digest that protein efficiently.

Weight loss isn't the same as fat loss

Every person I've encountered that starts a low-carb diet tells me how quickly they lose weight.

Great, but be careful. By reducing your carbohydrate intake, your muscles are less full with glycogen. Glycogen is the storage form of carbohydrate your body deposits within your muscles. If you're not eating as much carbs, you're not storing them either.

Additionally, when your body stores glycogen, it binds water along with it. For every gram of carbohydrate stored, you'll also store around 3 grams of water within your muscles.

Therefore, if you stop storing 250g of glycogen, you'll effectively lose 1kg on the scales (0.25kg glycogen and 0.75kg water).

Slow and steady when it comes to low-carb weight loss is better. Prioritise losing fat rather than losing weight.

Assess your happiness levels

Be honest with yourself and decide whether you actually feel happy and satisified following a low-carb lifestyle.

Does it make you feel good?

Nature allows our bodies to adapt to a wide range of lifestyles and dietary preferences. In some people, it can become a constant struggle against carbohydrate cravings and low blood sugar side effects on a low-carb diet.

If you don't feel good, consider adding a little carbohydrates back into your diet. Remember the trial and error approach.

Bear in mind, if you feel happy and effortless, you're more likely to stick with a lifestyle choice. In the end, consistency is what will determine your overall results and whether you hit your fat loss goal or not.

Paul Stokes Perth Personal Trainer Sports Nutritionist Group Fitness Instructor Massage Therapist

About the author

Paul Stokes

Paul Stokes BSc (Hons) is a Certified Personal Trainer, Accredited Sports Nutritionist, qualified Exercise to Music Instructor, Precision Nutrition coach, Massage Therapist and teaches 8 of the Les Mills Group Exercise programs.

He currently works in the Oil & Gas industry as a Wellness Coach, imparting his vast knowledge and experience to improve the quality of life of several hundred offshore workers.

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