Are carbs really bad for you?

Reducing carbs may seem like an easy way to get rid of unwanted kilos, but take care you’re not robbing your body of the fuel and nutrients it needs for optimal health.

University of Newcastle laureate professor of nutrition and dietetics, Clare Collins says the easiest way to understand carbohydrates is to think of it as you would fuel in the car – just as most cars need petrol so does your body need carbs to provide energy.

“There are different grades of carbohydrate, in the same way there are different grades of fuel for your car – not all fuels are equal and not all carbohydrates are equal,” Clare says. “There are real health gains associated with knowing which carbs to avoid and which to focus on.”

So, with the help of Clare, let’s explore what carbs are, the different types of carbs and how to make the healthiest choices to support your health and wellbeing.

Along with protein and fat, carbs are known as ‘macro-nutrients’. While protein is largely used for building muscle, and fat is useful for insulation and hormone production, carbohydrate is converted into energy that powers your whole body, including heart, lungs, muscles and brain.

Carbs are found in a wide array of food. “The foods that are really rich in carbohydrate are plants or those made from plants, so fruits and vegetables, legumes and grains,” Clare says.

This includes:

• Grains like bread, rice, pasta, oats and other cereals

• Fruits like bananas, blueberries, pears, apples and mango

• Starchy vegetables like corn, sweet potatoes, and peas

• Legumes like dried peas, lentils, chickpeas and soybeans and other dried beans

Wholegrains, legumes, fresh fruit and vegetables are examples of complex carbohydrates, and it’s these our body needs for optimal health and nutrition as they naturally come packed with other nutrients and fibre.

When plants are processed and turned into ‘refined’ carbohydrates we want (but don’t need), the health implications are clear. Energy-dense, nutrient-poor foods such as biscuits, pastries, lollies and soft drinks are examples of refined or ultra-processed carbs.

A recent systematic review of 43 research studies found that consuming ultra-processed food results in higher rates of obesity, metabolic syndrome, irritable bowel syndrome and some cancers.

“There are alarm bells going off in the research community about ultra-processed foods so really it's about avoiding them as much you can,” Clare says.

Consumed in their original or minimally processed form, carbs fuel the body with the energy it needs for bodily functions and physical activity.

Whole, carb-rich foods also contains the fibre your body needs for good bowel health and disease prevention, and vitamins essential for maintaining metabolism and energy levels. Wholegrains, in particular, are useful in lowering your risk for cardiovascular disease and specific cancers.

“The mistake many people make is lumping complex and refined carbs into the same group,” Clare says.

As well as speeding up how quickly a carbohydrate is absorbed into the body, ultra-processed carbs often have salt, fat and a range of types of sugar added to them – think potato crisps, biscuits and cake. As we all know, these hard-to-resist foods can be addictive and lead to weight gain.

Complex carbohydrates, on the other hand, are an important part of a healthy diet. It’s all about making good quality carbohydrate food choices.

Related: Weight loss fact and fiction

“If you want to reduce your carbs, reduce your junk carbs but keep your wholegrain carbs,” Clare advises. “Otherwise it’s like trying to drive a car without having enough fuel – you run out of petrol and end up in a worse state.”

Cutting carbs can lead to short-term weight loss, but Clare warns that the kilos soon return when you eat and drink normally again. If you don’t eat enough carbs, there are also some unpleasant side effects.

“The first thing you’ll notice is a lack of energy,” says Clare. “Longer term, you’ll probably develop constipation and bad breath, and if you really cut down your carbohydrates, the nutrient group you miss out on are the B vitamins, good sources of which are wholegrains, vegetables and legumes.”

B vitamin deficiency is rare but not getting enough can contribute to feelings of lethargy or changes in skin, cracks on the sides of your mouth or a red sore tongue, depending on the specific B vitamin.

“In this day and age, you can’t just do what your grandparents did, which is rely on the foods that are available in your environment,” Clare says. There has never been so much choice when it comes to food, and never have there been so many ultra-processed options to tempt us.

Clare advises looking for high health star ratings on food packaging and paying attention to ingredient and nutrition labelling. “Aim for minimally processed foods, look for how many wholegrains are in them, and consider how quickly they are digested and absorbed – this is measured by the glycemic index," Clare says.

“If you don’t want to be bothered with labels and health stars, cooking more at home with wholegrains and legumes and working out how to hide more vegetables in recipes are really valuable things to focus on.”

Adding lentils to a meat dish such as bolognese, for example, boosts the nutrient and fibre content and adds a chewiness factor. This means you’ll feel more satisfied with less food because your brain has been given enough time to register when you’ve had enough.

Consider how long it takes to eat baked beans on wholegrain toast (and how satisfied you feel afterwards) compared to eating doughnuts.

“You can probably scoff a six-pack of doughnuts by the time you’ve eaten the baked beans on toast,” Clare explains.

She suggests porridge or muesli as a great breakfast option and air-popped popcorn as a healthy wholegrain snack.

For more budget-friendly meal ideas, visit nib foundation program No Money No Time, a platform Clare and her team developed to make healthy eating quick and easy.

For personalised nutrition advice and support, find an accredited practising dietitian at Dietitians Australia.

No Money No Time is supported by nib foundation. We’ve committed over $21 million in funding to support 166 charity partners to deliver innovative programs that tackle important health issues. Learn more about nib foundation.

Please note: The tips throughout this article serve as broad information and should not replace any advice you have been given by your medical practitioner.