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 the same and it is the type and quantity of carbohydrate in our diet that is important.

"While we should reduce the amount of sugar in our diet, we should base our meals on starchy carbs. There is strong evidence that fibre, found in wholegrain versions of starchy carbs for example, is 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 about 18g a day.

What are carbs?

Carbohydrates are a 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 one of three macronutrients (nutrients that form a large part of our diet) found in food – the others being fat and protein. Hardly any foods contain only one nutrient and most are a combination of carbohydrates, fats and proteins in varying amounts. There are three different types of carbohydrate: sugar, starch and fibre.

  • Sugar is found naturally in some foods, including fruit, honey, fruit juices, milk (lactose) and vegetables. Other forms of sugar (for example table sugar) can be added to food and drink such as sweets, chocolates, biscuits and soft drinks during manufacture, or added when cooking or baking at home. Remember: sugar is a carbohydrate but not all carbs are sugars. Find out more about sugar.
  • Starch, made up of many sugar units bonded together, is found in foods that come from plants. Starchy foods, such as bread, rice, potatoes and pasta, 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 keep our bowels healthy and some types of fibre may help lower cholesterol. Research shows diets high in fibre are associated with a lower risk of cardiovascular disease, type 2 diabetes and some cancers. Good sources of fibre include vegetables with skins on, wholegrain bread, wholewheat pasta and pulses (beans and lentils). Find out more about fibre.  


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, starchy carbs release sugar into the blood more slowly than sugary foods and drinks.

Carbs should be the body’s main source of energy in a healthy balanced diet, providing about 4kcal (17kJ) per gram. Carbs 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 of energy.

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.

Calorie intake
Carbohydrate contains fewer calories gram for gram than fat, and starchy foods can be a good source of fibre, which means they can be a useful part of a weight loss plan. By replacing fatty, sugary foods and drinks with high-fibre starchy foods, it is more likely you will reduce the number of calories in your diet. Also high fibre foods add bulk to your meal helping you feel full. "You still need to watch your portion sizes to avoid overeating,” says Sian. “Also watch out for the added fats used when you cook and serve them: this is what increases the calorie content."


Should I cut out carbs?

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

However, cutting out starchy foods from your diet could put you at increased risk of a deficiency in 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 starchy foods, vegetables, fruits, legumes and dairy products 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 the amount of cholesterol in your blood – 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 buildup 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 to limit the amount of sugary foods you eat and instead include healthier sources of carbohydrate in your diet such as wholegrains, potatoes, vegetables, fruits, legumes and lower fat dairy products. Read the British Dietetic Association's review of low-carb diets, including the paleo, Dukan, Atkins, and South Beach diets.


Don’t protein and fat provide energy?

While carbs, fat and protein are all sources of energy in the diet, the amount of energy that each one provides varies:

  • carbohydrate provides: about 4kcal (17kJ) per gram
  • protein provides: 4kcal (17kJ) per gram
  • fat provides: 9kcal (37kJ) per gram

In the absence of carbohydrates in the diet your body will convert protein (or other non-carbohydrate substances) 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, 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.



Are carbs more filling than protein?

Carbs and protein contain roughly the same number of calories per gram, and fat contains almost twice as many calories per gram as carbs or protein. But other factors influence the sensation of feeling full such as the type and variety of food eaten, eating behaviour and environmental factors, such as portion size and availability of food choices. The sensation of feeling full can also vary from person to person. Among other things, protein-rich foods can help you feel full and we should have some meat, fish, eggs, beans and dairy products as part of a healthy balanced diet. But we shouldn’t eat too much of these foods. Remember that starchy foods should make up about a third of the food we eat and we all need to be eating more fruit and vegetables.



How much carbohydrate 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. This means that about half of your daily calorie intake should come from starchy foods, 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 a variety of fruit and veg a day. Go for wholegrain starchy foods whenever you can and eat potatoes with their skins on.


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 tooth decay and contribute to weight gain if you eat them too often, 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) which can benefit our health. The fibre in these foods can help to keep your bowels healthy and adds bulk to your meal helping you to feel full.

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.”


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) – 3.6g of fibre
  • one slice of wholemeal bread – 1.8g (one slice of white bread – 0.7g)
  • 230g serving of cooked wholewheat pasta – 10.1g (230g of cooked white pasta – 3.5g)
  • one medium (180g) baked potato (with skin) – 4.9g
  • 200g of baked beans – 7.4g
  • 1 medium orange – 2.7g
  • 1 medium banana – 1.1g 


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, when that food is eaten on its own. Some low GI 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. Also, the cooking method and eating foods in combination as part of a meal, will change the GI rating. 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.

Find out more about the glycaemic index (GI)


Do carbs make you fat?

Any food can be fattening if you overeat. It doesn't seem to matter a whole lot whether your diet is high in fat or carbs, but how much you eat in total. In fact, gram for gram, carbohydrate contains fewer than half the calories of fat. Wholegrain varieties of starchy foods and potatoes eaten with their skins on are good sources of fibre. Foods high in fibre add bulk to your meal and help you to feel full.

However, foods high in sugar are often high in calories and eating these foods too often can contribute to you becoming overweight. There is some evidence that diets high in sugar are associated with an increased energy content of the diet overall, which over time can lead to weight gain.

“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, we are advised 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.  


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 a wide range of foods, from bread, pasta and pizza, to cereals and many other foods. However, there is no evidence that wheat is more likely to cause weight gain than any other food. The point is if you consume more calories than your body needs, you will put on weight, regardless of the type of food you eat.

Unless you have a diagnosed health condition such as wheat allergy, wheat sensitivity or coeliac disease, there is little evidence that cutting out wheat and other grains from your diet would benefit your health. 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.

Find out if cutting out bread could help ease bloating or other digestive symptoms


Should people with diabetes avoid carbs?

Diabetes UK recommends that people with diabetes should try to eat a healthy balanced diet, as depicted in the eatwell plate, and to include starchy foods at every meal. Steer clear of cutting out entire food groups. It is recommended that everyone with diabetes sees a registered dietitian for specific advice on their food choices. Your GP can refer you to a registered dietitian.

Diabetes UK says there is some evidence which suggests 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. However, it is unclear whether the diet is a safe and effective way to manage type 2 diabetes in the long term. 

Weight loss from a low-carb diet may be because of a reduced intake of calories overall and not specifically as a result of eating less carbohydrate. There is also not enough evidence to support the use of low-carb diets in people with type 1 diabetes.

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.


What’s the role of carbs in exercise?

Carbohydrates, 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. 


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.

Page last reviewed: 22/09/2014

Next review due: 22/09/2016


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The 15 comments posted are personal views. Any information they give has not been checked and may not be accurate.

ko12 said on 22 November 2014

Oh dear, not much better than it was a year ago; I see you are still fighting hard to stay with non-existent/discredited science.

Anyway, as someone who switched 3 yrs ago to a LCHF lifestyle (dropping 36kg in 15 months, another 2kg since, losing 5 medications in the first 3-4 months and the remaining two since, improving almost all health markers, e.g. better BP with LCHF than HCLF+olmesartan+hydrochlorothiazide, TG down, HDL x2 etc., etc.) let me just make one suggestion about fibre; it is one that I follow myself, although I normally eat 2 squares (18g fibre/day from this source).

Eat a square of high cocoa content (preferably 100%) chocolate after each meal. Yummy with your coffee and that daily 30g/1oz provides about 9g fibre (and about 22% of iron RDA). Compare that with the 53g (about 2 servings) of Kellogg's All Bran you would need to match that fibre content (I would need to eat 100+g!). But maybe you prefer the taste of bran flakes to cocoa/chocolate...

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shenava said on 21 October 2014

I battled with weight loss for several years, Thinking a calorie controlled balanced diet was the way forward. It is absolute nonsense. I now live on a low carb diet, consisting of meat, cheese, nuts, low carb veg, I am now 3 stone lighter, recently had my bloods taken, testing full blood count, plasma glucose level, urea and electrolytes,liver function, serum TSH, cholesterol. All were fine, I now run and cycle regularly. I am fitter and healthier than I have been for years as tested and confirmed by the NHS and yet I live a dietry lifestyle that should be making me fat. I don't calorie count any more I eat when I want, I am not deficent in any vitamins or minerals. The rest of my family have switched to a low carb lifestyle and all have similar experiences.

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redandgold said on 19 October 2014

I clicked on a link which promised "We sort the wheat from the chaff to bring you the evidence-based truth about carbs" So where is the evidence? all I see is the same dogma that has been repeatedly preached and no actual evidence at all!

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Ianpa said on 01 September 2014

since switching to a low carb (not no carb) diet my endurance training has improved dramatically.I never feel tired or lethargic, so carbs don't have to be your main source of energy. By the way, I have also lost nearly 2 stones in weight and my blood pressure has fallen into the "ideal" zone. I eat loads of butter and cream ,lots of green veg and eggs, and about the same amount of meat as before ( but with the fat left on, which I used to trim off after years of 'brain washing'!).

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CynicalEng said on 27 May 2014

The update hasn't made a great improvement. The article still contains rubbish like :-

"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."

An unbiased article would point out that calories can be obtained from any of the three macronutrients and that your body has the largest energy store in the form of fats, not carbs.

Bacon and egg is a carb free breakfast, steak with two green veg has a few grams. Nobody advocates zero carb diets but restricting to <100 grams per day gives many people benefits to health.

If you want to lose weight reduce calories and make sure the ones you reduce are all carbohydrate - the optional macro nutrient.

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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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