Why does my body need carbohydrates?

Maya Aboukhater
Specialist Dietitian at Cromwell Hospital
24 February 2023
Next review due February 2026

Carbohydrates are an important part of a healthy diet. They provide us with energy, as well as essential nutrients that our body needs. But not all types of carbohydrate are good for us. Here, I talk about what carbohydrates are, where they come from, and how much the body needs.

family eating at a table

What are carbohydrates?

Carbohydrates are an important source of energy for your body. Fats and protein also provide energy, but carbohydrates are the preferred type of energy source for your brain and nervous system. Your body also uses carbohydrates to fuel activity in your muscles and keep other organs working properly.

Even when your body breaks down fat for energy, you still need a certain amount of carbohydrate for this process to happen properly.

Wholegrain, starchy carbohydrates are also an important source of other essential nutrients, including fibre.

What types of carbohydrates are there?

Carbohydrates in their natural form that haven't been processed can be thought of as ‘good carbs’ because they tend to be healthier. These include:

  • natural sugars found in whole fruit and vegetables, milk, and dairy products
  • wholegrain, high-fibre varieties of starchy carbohydrates

Sources of wholegrain and high-fibre carbs include:

  • wholegrain bread
  • brown rice
  • whole-wheat cereals
  • potatoes with the skin left on

These carbs provide a steady source of energy. They release sugar into your blood more slowly than sugary foods and drinks, or refined carbs like white bread. This can keep you feeling fuller for longer, helping to control your appetite and maintain a healthy weight.

The ‘free’ sugars added to processed foods and drinks – like biscuits, fizzy drinks, chocolate, and cake – can be thought of as ‘bad carbs’. These foods and drinks contribute to your energy intake by packing a lot of calories into a small volume, but often lack other useful nutrients. Free sugars are also naturally present in honey, syrups and fruit juices so it can be confusing to understand what’s good and bad. What’s important is to be aware of these free sugars and try to reduce your sugar intake when you can.

Processed or refined starchy carbohydrates, such as white bread, pasta and, cereals are less healthy than wholegrain options. This is because when grains are processed to look whiter, the part of the grain that contains fibre and many useful nutrients is removed.

How many carbohydrates do I need?

Aim to make starchy foods – ideally wholegrain starchy carbohydrates – about a third of your diet. Include things like wholemeal bread, brown pasta, or brown rice in every meal, as well as some fruits and vegetables. In general, a portion of carbohydrate for one meal should be about the size of your fist. The exact amount you need differs from person to person. It depends on many things, including your age and activity levels. As a minimum, adults should have 130g of carbohydrates.

Do all bodies react the same to carbohydrates?

The way carbohydrates affect your body can depend on if you have certain conditions. If you have diabetes, carbohydrate counting becomes very important. A registered dietitian can help you with this. While you have to watch your intake of sugary foods, this doesn’t mean you have to completely cut out carbohydrates. There are healthier sources of carbohydrates you can include in your diet such as fruit, vegetables, and wholegrains. These are foods with a low glycaemic index (GI). GI is a measure of how quickly carbohydrate in your food is digested and broken down into sugar molecules. Low-GI foods cause your blood sugar level to rise and fall slowly, so you feel fuller for longer.

Infographic: Healthy food swaps for a lower GI diet

The following infographic shows us some examples of healthy food swaps for a lower glycaemic (GI) diet. You can click on the image below to download a larger version of the infographic (JPG, 0.15 MB)

Infographic showing the Healthy food swaps for a lower glycaemic index (GI) diet

Should I eat a low carb diet?

Some diet plans, such as the paleo diet (also known as the caveman diet) and the Atkins diet are based on reducing the amount of carbohydrate you eat. However, there’s no evidence that diets like this are any more effective than diets that focus on reducing your fat intake. In addition, diets like this can be difficult to stick to, which won't help you to keep the weight off long-term. Low-carbohydrate diets often don’t leave room for the healthy carbohydrates in fruit, vegetables, and wholegrains, which contain essential nutrients.

Carbohydrates do contain calories but less than half the number found in fat. Of course, as with lots of things, it’s not good to have too much. If you eat more carbohydrate than your body can burn off as energy, the excess will be converted to fat. But carbohydrates are an important part of a healthy diet. Rather than eliminate carbohydrates from your diet, the key thing is to eat the right type. Glucose is the main energy source for your brain, nervous system and red blood cells, so it’s important you have enough in your diet.

The Bupa weight management plan is designed for people with a BMI over 30 (or over 27 if you have a weight related condition). The plan is designed to empower you to achieve and maintain a healthy weight in a sustainable way.
Discover more about our medicated weight loss plan.

Maya Aboukhater
Maya Aboukhater
Specialist Dietitian at Cromwell Hospital



Rasheda Begum, Health Content Editor at Bupa UK

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