Carbohydrates 101

Carbohydrates 101

Carbohydrates you say this to many people and they might think they are the devil especially if they are trying to loose weight an often the first element to be cut down on. I have to say I have never been on a diet and most diets for the reason that first have a 80-90% fail rate as while people may get the weight off people often struggle to keep it off permanently. Instead my theory to eating well is to make healthy but sustainable choices with everything in moderation and cooking everything fresh from scratch. Back to carbs, everyone can identify what food are carbohydrates but do you really know what they are, why we need them and how they impact your body? So let me explain everything you need to know about them.

What is a carbohydrate?

Carbohydrates are simply compounds that are made up of hydrogen, oxygen and carbon. Carbohydrates are generally sugars that are linked together to form different chains and structures.

What are the different types of carbohydrates?

There are three different types of carbohydrate dependant on how many sugar units make up the compound, mono, di and polysaccharides.


Monosaccharides are simple sugar made up of one unit these include fructose (sugar found in fruit), galactose and glucose they can be found in foods like table sugar, sweets and honey. Many of these foods don’t have much nutritional value apart from sugar; healthier options in this group would be to have a whole piece of fruit, as you will get more fibre, vitamins, nutrients and antioxidants.


A chain of two units of sugar mentioned above such as

  • Lactose: glucose + galactose which is found diary products like milk
  • Maltose: two glucose molecules
  • Sucrose: glucose + fructose

Complex carbohydrates:

Polysaccharides or complex carbohydrates are molecules with more than two units of sugars. If there are 3-10 sugars it is called an Oligosaccharides and if there are more than 10 sugars they are called a Polysaccharides. There are two types starches and dietary fibres and this is where you start to hear that not all carbs are created equally.


Then people mention carbohydrates they are generally talking about the starches so the bread, pasta, rice, grains, flour ect. Though there also some veg and fruits that have starch particularly in potatoes and root vegetables. These chains are joined together with alpha linkages, which can be easily broken down and therefore cause a quick and large increase in blood sugar.

Dietary Fibre:

Dietary fibres are normally deemed the ‘healthy carbs’ and they are non-starch polysaccharides. The molecules are linked together with beta molecules, which our bodies can’t actually digest. As foods higher in dietary fibre take longer to digest they also make you feel fuller for longer. Carbohydrates with fibre include root veg, nuts, oats, wholemeal products and fruit. Another function of fibre is to absorb any excess fats in the intestine where your food is broken down and is claimed to lower cholesterol levels.

Whole grain foods generally have a night nutritional value as they are less process and therefore haven’t had the germ or bran of the grain removed which can contain healthy fats, vitamin E and B. Research suggests that ever 28g of wholegrain can increase your life expectancy from can condition by 5% and 9% from cardiovascular related diseases.

Why do we need Carbohydrates?

Carbohydrates are our main source of energy for our bodies to enable you to function and keep all your organs running. They are also important in order to regulate the blood sugar levels, provide energy to avoid having to use protein. They also important in weight management as they give you the feeling of fullness, provide fibre and prevent constipation.

As you digest carbohydrates then will be broken down into the monosaccharide molecules or sugars. That’s why when you have any time of carbs it will cause and increase in your blood sugar levels. The sugar is then digested, the time will depending on type of carbohydrate. The sugar will then be transported round your body to be used for energy and in controlled by your pancreas producing an enzyme and hormone called insulin. Insulin will be released into the blood to tell your protein and fats cells to allow the absorption of sugars to then convert it into energy. Any sugar that we don’t need will then be taken to the liver and muscles to store it for energy for later. If there is excess in these stores it will then be converted to fat, hence why people tend to cut them down to promote weight loss.

If you don’t have enough carbohydrates then you can develop hypoglycaemia or low blood sugar, which can make you lighted or dizzy. It can also affect your concentration and make you feel weaker. This can happen with people that have diabetes or why sometimes after a hard workout you can feel lightheaded. Your body will then turn to break down fat in order to get some energy and then will move onto protein and your skeletal muscles.

There is a risk that if you body gets used to insulin you can become less sensitive to insulin, which can make you insulin resistance as your body will start have trouble controlling the body sugar levels in your body. This insulin resistance is what can lead to conditions like diabetes, heart disease and high blood pressure.

How many carbohydrates should we have?

In an average person diet roughly half (45-65%) of the calories or food we consume should be from carbohydrates. On average men should have around 38g and women should have 25g until the age of 50 when it starts to dip down again. You should aim to have starchier wholegrain carbohydrates rather than more simple variety as they not only give a slower release but also generally have high nutritional values.

Exercise and Carbohydrates

Carbohydrates are considered to have the most significant impact on exercise performance compared to any other part of nutrition. Athletes have been recommended to have higher percentages of carbohydrates with around 60%. (Devlin et al 1991) According to a 2004 study the percentage of carbohydrates in Ethiopian athletes was 64% and the Kenyans were higher with 76%. It is well known that before an endurance event it is important to carb load in order to maintain muscle glycogen in prolonged exercise. Research shows that you can store approx. 350g of muscle glycogen at one time. In a 30km run when the athletes increased their carbohydrate intake they all had faster times overall and higher splits in the last 10km of the run. (Williams et al 1992) A diet higher in complex carbohydrates in athletes compares to simple carbs showed a 3% increase in performance.

As for pre-exercise nutrition it has been proven that lower GI foods (the study used lentils with potatoes) showed an increase in improved endurance capacity compared to high GI foods. However you don’t want the meal to be too high in fibre or fat as this can stomach troubles during exercise and effect the rate of which carbs are absorbed.

Carbohydrates are essential to recovery from exercise as your daily carbohydrate intake may not be enough. If you don’t have enough carbs the risk to that your muscle glycogen will fall which will effect the strength and ability for your skeletal muscles to recover and rebuild. (Kirwan et al 1988) Furthermore it will also cause you to fatigue sooner as you will literally run out of fuel or ‘hit the wall’

What is glycemic index?

Glycaemic Index is the value given to food based on how much you need to increase your glucose or blood sugar level. This is a very important value especially if you have diabetes. The lower the number the slower it will take to increase the blood sugar and are what get deemed as slow energy release carbohydrates. While high glycaemic foods don’t take very long to increase your blood sugar theses include fruit juice, white bread, soft drinks and it may surprise you but carrots. These foods will cause a spike in your blood sugar but also cause a sharp fall later on. Medium glycaemic foods are normally food high in fibre that isn’t as easily absorbed and take longer to break down these includes fruit, veg and whole grains. While low glycaemic foods are normally food higher in protein such as eggs, cheese and meat. Medium and low glycaemic food will cause a slower rise and fall in blood sugar levels.

Carbohydrates and weight loss

Many people will go on low carbohydrate diets in order to loose weight. Research has been proven that a low carb diet does lead to bigger chances to a person metabolism compared to a high fat diet. The latest research seems to point to a higher increase in weight loss with 46% more on low cab diet compared to a low fat. However isn’t as effective in fat loss with the low fat dieters losing 67% more body fat. (Hall et al 2015) The rapid loss of weight and low carbohydrate diets are normally put down to a heightened water loss and therefore more research will need to be conducted to how sustainable it would be in the long term.

It has also been proven that a low carb diet will also decrease the amount of triglycerides, increase insulin sensitivity, decrease blood sugar levels and decrease insulin levels. (Samaha et al 2003) A study by Aude et al 2004 also shown that as well as an increase weight loss compared to high protein diets it also improved weight to hip ratio, lower cholesterol, triglycerides and the size of LDL particles.


Carbohydrates are important no matter what you need or what to achieve through your diet, whether you want to loose weight or exercise hard they are essential. The main thing to take from this is not to get carried away with cutting out carbs they are not created equal but if you stick to healthier options such as wholemeal, starchy vegetable, legumes or grains such as quinoa, lentils there is no need limit them. If you are doing hard exercise than it is important that you consider whether you are getting enough extra on those days in order to get the optimum performance and recovery.



Carbohydrates: Food Fact Sheet – The British Association of Dietiticans. 

Ted Talk:How do carbohydrates impact your health? – Richard J. Wood 

Carbohydrates in human nutrition. (FAO Food and Nutrition Paper – 66) 1999 

The Role of Carbohydrates in Exercise and Physical Performance- Food and agriculture organization of united nations 

Devlin, J.T., Williams, C. Foods, Nutrition and Sports Performance; a final consensus statement. Journal of Sports Sciences 1991; 9 (Suppl 9):iii.

Williams, C., Brewer, J., Walker, M. The effect of a high carbohydrate diet on running performance during a 30-km treadmill time trial. European Journal of Applied Physiology 1992;65:18-24.

Kirwan, J.P., Costill, D.L., Mitchell, J.B., Houmard, J.A., Flynn, M.G., Fink, W.J., Beltz, J.D. Carbohydrate balance in competitive runners during successive days of intense training. Journal of Applied Physiology 1988; 65:2601

Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity Hall, Kevin D. et al. Cell Metabolism , Volume 22 , Issue 3 , 427 – 436

Samaha FF, et al. A low-carbohydrate as compared with a low-fat diet in severe obesity. New England Journal of Medicine, 2003.

Aude YW, et al. The national cholesterol education program diet vs a diet lower in carbohydrates and higher in protein and monounsaturated fat. Archives of Internal Medicine, 2004.

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