What do carbohydrates do to the body? Here’s how they really work

A lot of us remember a time when carbs were the enemy and a low-carb diet was all the rage. We’ve learned a lot in the years since – about the crucial role carbohydrates play in the body, the health benefits of different types of carbohydrates, and what happens when you cut out carbs.

Thankfully, modern nutrition has taught us that carbohydrates are actually one of the most important food groups for the human body.

One of our favourite things to do is pass our knowledge on to you. So, without further ado, here is your simple guide to healthy carbohydrates.

What are carbohydrates?

Carbohydrates, or carbs for short, are one of the 3 key macronutrients. The others are fats and proteins [3].

The macro part means that we need these nutrients in large amounts. That’s because they are the body’s main source of energy.

In fact, carbohydrates are actually your brain’s favourite source of energy. Examples of carbohydrates include [1][3]:

• Grain products like bread, rice, pasta and cereal
• Fruits and fruit juices
• Vegetables, especially potatoes, sweet potato and corn
• Legumes like beans and chickpeas
• Dairy products like milk and yoghurt
• Sweeteners like sugar and honey
• Treats like biscuits, cakes and lollies 

You’ve probably guessed from this list that not all carbs were created equal. We’re going to dive into the different types of carbohydrates a bit later.

But first, we’re going to explore exactly what carbs do for your body and why you need them.

What do carbohydrates do in the body?

The headline is: carbohydrates provide energy to your body – every cell, organ, muscle and system runs because of them [1].

That’s the general gist of what you need to know, but if you'd like more background, here’s the science behind it.

When carbs reach your digestive tract, they are broken down into different types of sugars. The most common one is glucose.

Glucose is carried around your body in the bloodstream. When it reaches its destination, it needs to be transported from the bloodstream into your cells.

This is where your pancreas comes in. Your pancreas creates a hormone called insulin, which acts like a little bridge between the bloodstream and the cells.

When your body has soaked up all the glucose it needs for right now, it puts the rest in storage. This means it can be used for a boost of energy later – such as between meals, while you sleep or during exercise [2].

A majority of the carbs you eat will be used like this for energy, although some have a different function. Some carbohydrates contain fibre, which is important for your gut health [3].

What types of carbohydrates are there?

There are 3 types of carbohydrates: sugars, starches and fibre.

Sugars are an essential source of energy and come in many different forms, like glucose, sucrose (added sugar), fructose (from fruits) and lactose (from milk) [2]

Starches are a type of complex carbohydrate that contains lots of glucose. Good examples include: whole grains like bread, rice, pasta and oats, plus potatoes, and chickpeas [4]

Fibre is a type of complex carbohydrate that your body can’t digest. It supports your digestive system by promoting good bacteria, helping food move through your gut and supporting healthy bowel movements [4]

Each type of carbohydrate has a different purpose in your body, which means all of them are important as part of a balanced diet. But not all types of carbs are considered healthy.

Simple carbohydrates vs complex carbohydrates

Once upon a time, we put carbs into 2 rather restrictive groups. There were the good carbs, known as complex carbohydrates, and the bad carbs, known as simple carbohydrates.

Simple carbohydrates are foods whose chemical makeup includes 1-2 sugar molecules. Your body breaks down these simple sugars quickly, which means they are a source of immediate energy.

But, they can also lead to blood sugar spikes [4]. Examples of simple carbs include: soft drinks, pastries and white bread.

Complex carbohydrates are foods whose chemical makeup includes 3 or more sugar molecules. This makes them slower to digest, which means less impact on your blood sugar. Examples of complex carbs include: whole grains, fruits and vegetables [4].

You can see how easy it was to decide which carbs to eat based on this system. But, over time, we realised that we hadn’t captured the full picture.

For example, quite a few fruits could fall on the simple carbs list. But we know fruit is better for you than pasty (even though it’s delicious).

We’ve now come up with a new system called the glycaemic index (GI) [1][6]. Here’s how it works.

Explaining the Glycaemic Index (GI)

The glycaemic index is a system that measures how quickly your body can process carbs into sugars, which also determines how fast your blood sugars rise [1].

Foods are scored from 0-100 and given a ranking of either high-, medium- or low-GI. A healthy diet will have foods from all categories, with a focus on mostly low-GI foods that help you feel fuller for longer and balance blood glucose levels [2].

The GI score is a good starting point, but it’s still only one measure. If you’re working on diet changes, then we highly recommend seeking support from a dietitian or other health professional.

How many carbohydrates do you need?

According to health experts, carbohydrates should make up between 45%-65% of your daily diet. This should also include at least 30g of fibre each day [4].

While it’s technically possible to eat all your carbs in the form of French fries, we don’t recommend it. The quality of carbs in your diet is just as important as the quantity [5].

So, what are some healthy carbs for your plate? Here’s what the Australian Dietary Guidelines say [2]:

• 4-6 serves of grains each day: where 1 serve is equal to a cup of cooked rice or a single slice of bread
• 5 serves of vegetables each day: where 1 serve is equal to one-half to a whole cup per vegetable
• 2 serves of fruit each day: where 1 serve is equal to a single medium-sized piece of fruit, such as an apple

Do all bodies react the same to carbohydrates?

Even though carbs are an essential food group, not all bodies have an easy time digesting them. For some people, it’s genetics, while others have a medical reason. Here’s what you should know. 

Genetics

Thanks to a recent study completed in America, we have a better understanding of how certain genes play a role in your ideal diet.

The POUNDS Lost study was a comparison of different diets and their effects on body composition [7]. It was a 2-year trial with over 800 participants.

Diet variations included different amounts of fats, protein and carbs, with weight loss achievable on all of them. But an interesting finding was that your genes could affect which diet was best for your body.

For example, one gene was linked to how people process carbs. People with this genetic profile had a higher chance of weight loss on a low-carb diet (35%) or weight gain on a high-carb diet (65%).

If you'd like more personalised advice and support on your weight loss journey, you might like to consider Juniper’s Weight Reset Program.

Juniper offers medically-backed weight loss treatments, but with the additional support and one-on-one health coaching for long-term, sustainable weight loss and weight management.

That means you can enjoy your favourite foods while working towards sustainable results, with expert guidance every step of the way. Because weight loss shouldn’t be about restriction — it should be about empowerment, balance, and finally feeling in control.

Allergies and medical conditions

Some people have issues digesting carbs because of an allergy, intolerance or medical condition. Examples include lactose intolerance, gluten intolerance and type 2 diabetes [4][1].

If you think your body might have issues with carbs, it’s important to work with your doctor on a diagnosis. They can also support you with treatment options, lifestyle and diet plans. 

What are the symptoms of too many carbohydrates?

We’re going to repeat something we said earlier: the quality of your carbohydrate intake is just as important as the quantity [5].

A big issue is having too many refined foods – like biscuits, lollies or sauces [2]. Sugary foods like these can lead to teeth problems like decay or cavities [4].

They can also impact your weight. Highly refined carbohydrates are broken down quickly by your body. This puts extra strain on your liver, which has to find a way to process or store them [8].

Any excess carbs that your liver can’t handle are turned into fat, which is why carbs can get a bad rep when it comes to weight gain [2].

Modern, sedentary lifestyles increase the risk that carbs can turn into body fat. That’s because we’re not using as much energy throughout the day, which means we're more likely to have extra glucose in our bodies.

What happens if you don’t eat enough carbohydrates?

When it comes to carbs, we need to remember that they are an essential source of energy for your body's cells and organs – especially the brain [3].

If your diet is low in carbohydrates, then it’s likely to show up in symptoms such as [3][9]:

• Loss of concentration, irritability or mood changes
• Feeling fatigued because your body is low on energy sources
• Feeling hungry all the time because your diet is too low in calories
• Digestive issues because your diet lacks fibre

Finally, there is a chance that your body will start chewing up muscle to use as energy. This can happen if your diet is lacking in any of the 3 key macronutrients – carbs, fats or protein [3].

The best way to ensure your diet is full of nutrients is to work with a dietitian on a personalised plan.

Make carbs one part of a balanced meal

We’ve really dived deep when it comes to all things carbs. But one thing we haven’t covered yet is how to fit them into your diet.

While we always recommend working with health professionals for personalised advice, we can offer a few general tips to get you started.

Include all 3 macronutrients

Whenever we talk about a balanced diet, what we really mean is that the food in your day is made up of a good mix of nutrients. The same goes for a balanced meal – it’s all about filling your plate with a combination of healthy foods.

The easiest place to start is the macronutrients. Remember, carbs are 1 of 3 macronutrients your body needs [3]. That means eating plenty of carbs, protein and fats at every meal.

Check the GI score

In simple terms, having lots of high-GI foods tends to increase your risk of serious disease and obesity, while low-GI foods are recommended to support a healthy weight [6].

A healthy diet can contain all different GI scores, including some treat foods [1]. For a personalised diet plan, we recommend working with a dietitian or your doctor.

Look for healthy swaps

One of the best ways to use the GI system is to make healthy swaps in your diet. For example, if you usually enjoy cereal for breakfast, then a hearty bowl of porridge might be just as satisfying and lower GI [1].

Other good swaps include [5]:

• Trade fruit drinks for whole fruit, which usually has half the sugar and twice the fibre
• Swap starchy carbohydrates like potatoes for fibre-packed legumes like chickpeas and beans, which have a similar texture
• Replace refined grains like white bread with whole wheat bread, or swap your lunchtime sandwich for a whole grain salad using brown rice

Find a diet and lifestyle you enjoy

An interesting insight from the POUNDS Lost study was that there is no single diet that is ideal for every person. But, there were a few diet and lifestyle habits that worked well for most people, such as [7]:

• Eat foods high in fibre and protein
• Having fewer ultra-processed foods
• Focus on physical activity
• Get plenty of quality sleep 

The other intriguing outcome is one that we fully support – the ideal diet will be tailored to the individual and one that they find easy to follow.

Improving your health isn’t about drastic changes that make life harder. It’s about taking small steps toward a healthier lifestyle that you find easy to fit in and maintain for the long-term.

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