The truth about carbs

"Carbs" has become a dirty word in recent times, especially in the weight loss world, due in no small part to the popularity of low-carb diets such as the Atkins, Dukan and South Beach.

The "carbs are bad" mantra from Dr Atkins and co has left many people confused about carbohydrates and their importance for your health, including maintaining a healthy weight.

Dietitian Sian Porter says: "Carbohydrates are such a broad category and people need to know that not all carbs are bad.

"While we should reduce the amount of sugar in our diet there is strong evidence that starch and fibre are good for our health.”

Find out all you need to know about carbohydrates, their health benefits, healthier sources of carbs and how carbs can actually help you lose weight.


Many people don't get enough fibre. We are advised to eat an average intake of 18g a day

What are carbs?

Carbohydrates are a major source of energy. When eaten, the body converts most carbohydrates into glucose (sugar), which is used to fuel cells such as those of the brain and muscles.

Carbohydrates are not a food group like fruit, vegetables, starches and dairy foods. Carbohydrates are one of three macronutrients (nutrients required in large amounts) found in food – the others being fat and protein. Lots of foods contain all three in varying amounts.

There are three different types of carbohydrate: sugar, starch and fibre. Most carbohydrate foods contain a mixture of all three types in varying amounts.

  • Sugar is found naturally in some foods, including fruit, fruit juices, milk (lactose) and vegetables. Other forms of sugar (for example table sugar) are also added to processed foods and drinks such as sweets, chocolates, biscuits and soft drinks. Remember: sugar is a carb but not all carbs are sugars. 
  • Starch, made up of many sugar units bonded together, is found in foods that come from plants. Starchy foods provide a slow and steady release of energy throughout the day. Find out more about starchy foods.
  • Fibre is only found in foods that come from plants. Fibre helps with digestion and may help lower cholesterol. Good sources of fibre include vegetables with skins on, wholegrain bread, wholewheat pasta and pulses (beans and lentils). Find out more about fibre.


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Why do we need carbs?

Carbs are important to your health for a number of reasons. In a healthy balanced diet they are the body’s main source of energy. High fibre, slow release carbs help regulate sugar levels in the blood.

Carbs should be the body’s main source of energy in a healthy balanced diet, providing 4kcal (16.8kJ) per gram. Whether you eat starchy foods or sugary foods, both are broken down into glucose (sugar) before being absorbed into the bloodstream. From there, the glucose enters the body’s cells with the help of insulin. Glucose is used by your body for energy, fuelling all of your activities, whether going for a run or breathing. Unused glucose can be converted to glycogen found in the liver and muscles. If unused, glucose can be converted to fat, for long-term storage.

Disease risk
Vegetables, pulses, wholegrain varieties of starchy foods, and potatoes eaten with their skins on are good sources of fibre. Fibre is an important part of a healthy balanced diet. It can promote good bowel health, reduce the risk of constipation, and some forms of fibre have been shown to reduce cholesterol levels. Many people don't get enough fibre. On average, most people in the UK get about 14g of fibre a day. We are advised to eat an average of 18g a day.

Weight reduction
Starchy foods are low in calories and can be a good source of fibre, which means they can be a useful part of a weight loss plan. Research suggests that people who eat lots of fibre, especially whole grain foods, tend to have a healthier weight. “The fibre physically fills you up and takes longer to digest, meaning you feel fuller for longer,” says Sian. "Just watch out for the added fats used when you cook and serve them: this is what increases the calorie content." 


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Don’t protein and fat provide energy?

While carbs, fat and protein are each a source of energy, the amount of energy that each one provides varies:

• carbohydrate provides: 4kcal per gram
• protein provides: 4kcal per gram
• fat provides: 9kcal per gram

In the absence of carbohydrates your body will convert protein and fat into glucose, so it's not just carbs that can raise your blood sugar and insulin levels.

If you consume more calories than you burn from whatever source, such as carbs, protein or fat, you will gain weight. So cutting out carbs or fat does not necessarily mean cutting out calories if you are replacing them with other foods containing the same amount of calories.

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Are carbs more filling than protein?

The sensation of feeling full can vary from person to person and is influenced by the type of food eaten, eating behaviour and environmental factors, such as portion size. Protein helps to make you feel full and forms part of a health balanced diet, as described by the eatwell plate.

Carbs help you feel full by providing bulk, like filling up your plate with vegetables so you feel you are getting a plateful and providing fibre to fill you up and slow digestion. In addition, some carbs are low GI such as brown basmati rice, porridge and new potatoes, which means they take longer to digest, thereby keeping blood sugar levels stable.


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How can I increase my fibre intake?

To increase the amount of fibre in your diet, go for wholegrain varieties of starchy foods and eat potatoes with skins on. Try to aim for an average intake of 18g of fibre a day. Here are some examples of the typical fibre content in some common foods:

  • two breakfast wheat biscuits (approx. 37.5g) – 3.9g of fibre
  • one slice of wholemeal bread – 1.8g (one slice of white bread – 0.7g)
  • 230g serving of wholewheat pasta – 8.1g (230g of white pasta – 2.8g)
  • One medium (180g) baked potato (with skin) – 2.5g
  • 200g of baked beans – 7.6g
  • 1 orange – 2.7g
  • banana – 0.8g  


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How much carbs should I eat?

The Government’s healthy eating advice, illustrated by the eatwell plate, advises that a third of your diet should be made up of starchy foods, such as bread, rice, potatoes and pasta, and another third should be fruit and vegetables. Data from the National Diet and Nutrition Survey, which looks at food consumption in the UK, shows that most of us should also be eating more fibre and starchy foods and fewer sweets, chocolates, biscuits, pastries and cakes. Try to aim for at least five portions of fruit and veg a day. Go for wholegrain starchy foods whenever you can and eat potatoes with their skins on


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What carbs should I be eating?

Sweets, chocolates, biscuits, cakes and soft drinks with added sugar are usually high in sugar and calories, which can increase the risk of dental cavities and contribute to weight gain, while providing few other nutrients.

Fruit, vegetables, pulses and starchy foods (especially wholegrain varieties) provide a wider range of nutrients (such as vitamins and minerals) that are good for you. The fibre in these foods can help to keep your bowels healthy and can help you feel full for longer, which means we're less likely to overeat. 

Sian says: “Cutting out a whole food group (such as starchy foods) as some diets recommend could put your health at risk because as well as cutting out the body’s main source of energy you’d be cutting back essential nutrients like B vitamins, zinc and iron from your diet.” 


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Research suggests low-carb diets don’t result in greater weight loss over time than healthy balanced diets

Can eating low GI (glycaemic index) foods help me lose weight?

The glycaemic index (GI) is a rating system for foods containing carbohydrates. It shows how quickly each food affects glucose (sugar) levels in your blood. Some low GI unprocessed foods, such as wholegrain foods, fruit, vegetables, beans and lentils are foods we should eat as part of a healthy balanced diet. However, using GI to decide whether foods or a combination of foods are healthy or can help with weight reduction can be misleading.

Although low GI foods cause blood sugar levels to rise and fall slowly and therefore may help you to feel fuller for longer, not all low GI foods are healthy. For example, watermelon and parsnips are high GI foods, while chocolate cake has a lower GI value. Therefore, relying on GI alone is not a reliable way to decide whether foods or combinations of foods are healthy or will help you to lose weight.


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Do carbs make you fat?

If Dr Atkins has instilled one message into our weight-conscious minds, it is that carbs are fattening. Any food can be fattening if you overeat. It doesn't seem to matter a whole lot whether your food is high in fat or carbs, but how much you eat in total. In fact, gram for gram, starchy foods contain fewer than half the calories of fat. Wholegrain varieties of starchy foods and potatoes eaten with their skins on are good sources of fibre. Fibre can help you to feel full, which means you're less likely to overeat and put on weight. However, foods high in sugar are often high in calories and eating these foods too often can contribute to you becoming overweight.

“When people cut out carbs and lose weight, it’s not just carbs they’re cutting out, they’re cutting out the high-calorie ingredients mixed in or eaten with it such as butter, cheese, cream, sugar and oil,” says Sian. "Eating too many calories – whether they are carbs, protein or fat – will contribute to weight gain.”

To maintain a healthy weight, the advice is to cut down on sugary foods in favour of fruit, vegetables, pulses, wholegrain starchy foods and potatoes with skins on, while still keeping a watchful eye on portion size.


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I need to lose weight, should I cut out carbs?

This is the theory behind many popular diets such as the Atkins, Dukan and South Beach diets. By cutting out carbs, the body turns to fat stores for energy and weight loss is said to follow.

There is a growing body of research suggesting that low-carb diets can be an effective weight loss tool. However, there are concerns that low-carb diets high in saturated fat may raise the risk of heart disease and stroke.

Short-term studies suggest that low-carb diets can result in greater weight loss than low-fat diets, but these differences are not sustained over time. Below is a selection of recent systematic reviews – often considered the gold standard of scientific research – on low-carb diets:

  • A 2013 review of 13 studies involving 1,569 participants concluded that those assigned to a very-low-carbohydrate ketogenic diet (VLCKD) achieved greater long-term (at least a year) reductions in body weight and certain cardiovascular risk factors than those assigned to a low-fat diet. The authors concluded that a VLCKD "may be an alternative tool against obesity".
  • Another review from 2013 of 17 studies involving 1,141 obese patients suggested that low-carb diets "had favourable effects on body weight and major cardiovascular risk factors", although the effects on long-term health were unknown.
  • A 2009 study comparing low-carb diets with low-fat diets examined 13 studies involving 1,222 participants, concluded that low-carb diets were "more effective at six months" and were "as effective, if not more" as low-fat diets at 12 months.

Other research suggests that over periods of 12 months and beyond, low-carb diets fare no better than low-fat diets and there is some concern about the long-term health impact. There is strong and consistent evidence that reducing your calorie-intake is more important for losing weight than changing the proportion of carbs, fat and protein in your diet:

  • A 2013 report on the safety of low-carb diets reviewed 17 studies involving more than 272,000 people and found low-carb diets were "associated with a significantly higher risk" of death and no reduction in the risk of cardiovascular disease.
  • A 2006 review comparing low-carb diets with low-fat diets examined five studies involving 447 individuals found that those on a low-carb diet had lost more weight than those on a low-fat diet at six months but not at 12 months.
  • A 2004 review of the long-term benefits of various weight loss methods analysed 26 studies and found no evidence that low-carb diets resulted in greater weight loss than low-fat diets over the long term. 

The weakness of current research is that most studies are short term and of varying quality and there is a recognised need for longer-term, rigorous evaluation. Moreover – and this applies to most research on diets – it is notoriously difficult to study the effects of diet on health because people don't live in labs, they live in the real world and are exposed to different lifestyle and environmental factors, which can influence the results. 


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Can cutting out wheat help me lose weight?

Some people point to bread and other wheat-based foods as the main culprit for their weight gain. Wheat is found in everything from bread, pasta and pizza, to cereals and many other processed foods. Some "wheat-haters" argue that wheat is highly addictive, causing some people to want to eat more, especially high-calorie foods.

However, there is little evidence to support these claims. A narrative review, entitled 'Does wheat make us fat and sick?', concluded there was no evidence to support claims that wheat was bad for our health. The Turkish, the authors say, historically ate wheat as their main source of energy without people gaining weight. The obesity problem is also spreading to populations that eat little wheat, such as several Asian countries. Addressing the claim that a substance called gliadin contained in wheat is addictive, researchers found no published research to support this. They conclude there's "no evidence that gliadin either stimulates appetite or induces addiction-like withdrawal effects".

On the other hand, there is good evidence that a diet high in wholegrains and pulses can help reduce weight gain. A 2008 systematic review based on 53 studies found that a calorie-controlled diet high in cereals, especially wholegrains, can help achieve "significant weight loss". The review also concluded that evidence that refined grains, such as bread, was to blame for increased waist size in women was weak. Go Grains Health and Nutrition Ltd sponsored the review but had no role in writing it.


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Does eating wheat raise blood sugar levels?

"Two slices of whole wheat bread increase blood sugar higher than table sugar, higher than many candy bars," claims William Davis, author of Wheat Belly, which argues that wheat is bad for our health. He says eating lots of wheat-based products leads to frequent rises in insulin, which, in turn, creates insulin resistance, the condition that leads to diabetes.

While there isn't any evidence to support this claim, several studies have found a beneficial association between wholegrains, including wholegrain wheat, and insulin resistance. A 2004 study involving 2,834 people concluded that a diet high in fibre, wholegrains, cereal and fruit was "associated with significantly less insulin resistance". A 2003 study on wholegrain intake and insulin sensitivity involving 978 participants found that eating lots of wholegrains improved insulin sensitivity (the body's ability to lower blood glucose levels).



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Are carbs bad for our health?

Wheat and grains in general are the latest scourge of the health world. Grains, including wholegrains, have been blamed for a multiplicity of ills from dandruff, diabetes and dementia, to arthritis, schizophrenia and obesity.

A new market has sprung up on the back of the "wheat-is-evil" trend, including expensive gluten-free products and a wide range of grain and gluten-free diets. However, unless you have a diagnosed health condition such as wheat allergy, wheat sensitivity or coeliac disease, the evidence for cutting out wheat and other grains from your diet is very weak. Grains, especially wholegrains, are an important part of a healthy balanced diet. All types of grains provide carbs, vitamins and minerals. Grains are also naturally low in fat.


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Should people with diabetes avoid carbs?

This question has divided researchers, doctors and dietitians, as well as people with diabetes themselves. Diabetes UK says cutting back on carbohydrates – especially in terms of portion size – can have some health benefits for people wanting to lose excess weight. There is also evidence that low-carb diets can lead to weight loss and improvements in blood glucose control in people with type 2 diabetes in the short term, but there is not enough evidence to support the use of low-carb diets in people with type 1 diabetes. It is also unclear whether the diet is a safe and effective way to manage type 2 diabetes in the long term.

Douglas Twenefour, Diabetes UK clinical adviser, says: “When considering a low-carbohydrate diet as an option, people with diabetes should be made aware of possible side effects such as the risk of hypoglycaemia (low blood sugar). We also advise that people with diabetes discuss the amount of carbohydrate to be restricted with their healthcare team.

“The best way to manage diabetes is by taking prescribed medications and by maintaining a healthy lifestyle that includes plenty of physical activity and a balanced diet that is low in saturated fat, salt and sugar and rich in fruit and vegetables, without completely cutting out any particular food groups.”

Read Diabetes UK's review of the evidence from 1998 to 2009 on low-carb diets and their conclusions.


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Can we survive without carbs?

While we can most certainly survive without sugar, it would be quite difficult to eliminate carbs entirely from your diet. Carbs are the body's main source of energy. In the absence of carbs, your body will use protein and fat for energy.

However, cutting out healthy sources of foods containing carbs from your diet could put you at increased risk of deficiency of certain nutrients leading to health problems (see above), unless you're able to make up for the nutritional shortfall with healthy substitutes.

It may also be hard to get enough fibre which is important for a healthy digestive system and to prevent constipation. Healthy sources of carbs such as wholegrains, vegetables, fruits, legumes and dairy are an important source of nutrients such as calcium, iron and B vitamins.

Cutting out carbohydrates and replacing those calories with fats and higher fat sources of protein could increase your intake of saturated fat, which can raise your cholesterol which is a risk factor for  heart disease. 

When you are low on glucose, the body breaks down stored fat to convert it into energy. This process causes a build up of ketones in the blood, resulting in ketosis. Ketosis as a result of a low carbohydrate diet can be accompanied by headaches, weakness, nausea, dehydration, dizziness and irritability particularly in the short term.

Try limiting your carbohydrates to healthier sources such as wholegrains, vegetables, fruits, legumes and lower fat dairy rather than cutting them out completely. Read the British Dietetic Association's review of low-carb diets, including the paleo, Dukan, Atkins, and South Beach diets.


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What’s the role of carbs in exercise?

Carbs, fat and protein all provide energy, but exercising muscles rely on carbohydrates as their main source of fuel. However, muscles have limited carb stores (glycogen) and they need to be topped up regularly to keep your energy up. A diet low in carbs can lead to a lack of energy during exercise, early fatigue and delayed recovery. Fat and protein are harder to turn into energy than carbs, which means you may feel low on energy during your exercise session.


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When is the best time to eat carbs?

When you should eat carbohydrates particularly for weight loss is the subject of much debate, but there's little scientific evidence that one time is better than any other. “You should have some starchy carbs in appropriate portions with most meals, choosing high-fibre varieties whenever you can,” says Sian.


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Page last reviewed: 04/12/2013

Next review due: 04/12/2015


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The 10 comments posted are personal views. Any information they give has not been checked and may not be accurate.

munim786 said on 12 April 2014

There are essential Amino and Fattty acids but I have never heard or essential carbs. Carbs especially refined sort are the cause for obesity and excessive insulin which both combined are disastrous to the biological function and yet the NHS prescribe this diet (high insulin diet) which I find a real irony. NHS how much did you get paid by our sugar industry for this article?

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ItalianKitten said on 05 March 2014

I hold the NHS very highly, therefore I am acutely embarrassed by the bad science in this article.

Due to my recent diagnosis of diabetes I've been reading a lot of peer reviewed modern studies, and I'm becoming more and more mystified and frustrated by the nutritional advice by the NHS.

Frankly, your recommended low-fat high-carbs regime is almost the last thing diabetic people should eat, which is bad news as correct nutrition is the first line of defence against diabetes.

I'm going with Sweden and their sensible LCHF approach, instead. They're at the forefront of research on obesity and diabetes, whereas you're still using 40 years old fallacious and financially biased science from the United States.

As Mary Dan Eades, M.D. said: "The USDA food pyramid isn't about health. It’s about selling agricultural products." And the rest of the world went along with it.

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Shukor said on 29 January 2014

The article has been updated following comments left below and around the site. Steven, Live Well editor.

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stevie7v said on 25 January 2014

Have the NHS been infiltrated by certain members of the food lobby or are they really this ignorant?

No wonder this country has an obesity crisis!

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SodiumV said on 03 January 2014

Dreadful article. Old 70's health myths dressed up as common sense advice.
I do not understand how this is allowed to be put out as public information from the NHS.

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Ian UK said on 22 December 2013

Hello Sian, I am concerned that you are pushing the low fat dogma despite the relentless science and research that shows that the dogma is nonsense. The NHS has a public duty to admit low fat calorie obsession is a dead end. You do not deal with hormones, metabolism and gut health. Food quality and healthy metabolism are key to health, not carbs. Please stop defending the mistakes of the past.

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PhilTUK said on 21 December 2013

This is a very unbalanced article. It's fine as a "pro carbohydrate" item but needs to be balanced by an article stating the opposing case based on the insulin hypothesis of obesity and the problems of carbohydrates in diabetes etc.

There is a problem with the "science" above in that the article does in fact demonstrate a statistically significant improvement in weight loss at both months 3 and 6 of around 4% of weight loss. Most of us would take an extra weight loss of 3 to 4 kg in 6 months and say "thankyou very much, Dr Atkins". That could be an extra half stone to some of us.

At 12 months with a high dropout rate and the use of "baseline data carried forward" for the dropouts the weight loss difference is reduced to a mere 2% of body weight with P=0.26 so there is still an 80% probability of getting a better weight loss on the low carb arm of this one study.

This article should be withdrawn and re-written.

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Bart Kay said on 20 December 2013

9. Perfectly sufficient fibre and associated food factors such as vitamins can be gained from a diet based on leavy greens and raw coloured vegetables.

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Bart Kay said on 20 December 2013

This commentary is full of inaccuracy, fallacy, opinion, and error. Point wise:

1. Fibre is a carb. strictly, but it is not digested or metabolised, so should not be described nutritionally as a carb.
2. We do not need carbs at all - none.
3. Starchy foods when cooked do not release energy slowly, they dump glucose into the blood quickly. This is contraindicated - utterly.
4. There is no requirement, and no reason why grains need to be in the human diet at all.
5. Carbs are the main source of energy when they make up the largest portion of intakes, sure - but there is no reason why this needs to be so. Fats and protein also contain energy.
6. So what if fats contain 2.25 x the energy per g than carbs? If carbs cause you to eat 3 to 4 times as much total energy per day (which they do, due to insulin response).
7. Glycogen shortage is not a problem during exercise in properly fat adapted individuals.
8. This author has provided no supporting literature at all, it is an opinion piece, its full of ridiculous errors and fallacies, and its plain ignorant. NHS choices, really; come on.

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Bill UK said on 20 December 2013

I have been low carb for over a year. Result ; lower triglycerides, ldl static, hdl increased, fasting blood sugar lowered, energy levels increased. Oh and not to mention two and a half stone lighter. I eat lots of saturated fat and enjoy it. Am i constipated? No.

You need to examine the huge and growing scientific evidence on low carb high fat diets.

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