Carbohydrates: Friend or Foe?

Lee Smith Nutrition

We, as a civilisation, are on the verge of a global epidemic. Over the past three decades, people are becoming more overweight and obese than ever before [1]. But why is this? Is it an increase in lethargy? An increase in technological advances that require less effort on our part? Or is it an increase in poor food choices? Whatever the hypothesis, it’s incredibly common to hear that foods which contain carbohydrates are bad. Very bad! But calm yourself down for just one second… Carbs can’t be the enemy, can they?

What are carbs?

Firstly, let’s understand what a carbohydrate is. A carbohydrate is one of the four major biomolecules required by the body to function efficiently (alongside protein, fat and water). Consisting of carbon, hydrogen and oxygen, carbohydrates are also widely understood to be an essential source of energy for a fully functioning organism [2]. It has also been widely recognised that the human brain operates predominantly on glucose, another form of carbohydrate categorised as a simple carbohydrate [6]. What determines whether a carbohydrate is simple or not is how quickly it can be absorbed in to the blood stream. The faster the absorption, the quicker the blood sugar level increases. Most simple sugars (monosaccharides) do not contain any extra nutrients or minerals. Complex carbohydrates (polysaccharides) are starchy foods formed by longer saccharide chains, which means they take longer to break down in the gut [3].Starchy-foods.

The Glycaemic Index

The FSA Dietary recommendations advocate eating a balanced diet where carbs amass 50% of the diet [4] with the Glycaemic Index classifying a food by how high and for how long it raises blood glucose levels. The GI has previously been used in the Diabetes population but the general public has gained interest in recent years. It is believed that the lower the GI a food has been given the less it releases insulin thus helping to keep blood sugar levels under control [5]. However, this isn’t always the case. The GI investigates food items ingested on their own, not taking into account other variables such as time of day eaten, other foods it is eaten with and how much of the food is eaten at a given time. This can alter the GI of a food significantly [5]. Rather, it may be best to investigate the amount of GI a particular meal has. But given the huge variability on meal constructs, it can be incredibly difficult to investigate. This is where a little common sense is used. A box of chocolates is probably going to rapidly raise your blood sugar very high in comparison to a large fibrous, protein rich meal with a desert on the side. Both contain simple sugars, but both can affect the bloodstream very differently.

Simple sugars are easily accessible to everyone.

Simple sugars are easily accessible to everyone.


The biological hazard with increasing blood sugar is the resulting response by the body’s endocrine system. The endocrine system is responsible for managing the release and level of hormones in the body. One of these hormones is Insulin, a hormone designed to store excess blood sugars (as thicker, more sugary blood is dangerous to our organs) [5]. When we eat a simple sugar, due to its high absorption by the gut, our blood sugar levels increase causing further increases in Insulin. Insulin stores the sugar, and our blood sugar levels decrease again. This possibly gives reason for when we eat something high in sugar, we are in search of another sugar source shortly after. And so the cycle begins! Cue – another member of the obesity epidemic.

This is why some people run from carbs, because it is usually the simple carbs like cakes and sweets that we indulge on, thus giving carbs the bad name. But carbohydrates, in particular the complex sorts, are very beneficial to the body. Athletes are incredibly appreciative of carbohydrates. When vast sources of fuel is required, throughout physical exertion for instance, carbohydrates provide that release of energy. Especially the scary simple sugars that we are often told to avoid. Many athletes will ingest a simple carbohydrate source to quickly replenish glycogen (stored glucose in the muscle) to further enhance performance and prevent fatigue [5]. The problem here, as previously stated, is that many people eat these simple carbohydrates despite not exercising!

Complex carbohydrate foods are a fantastic food source that is rich in nutrients and vitamins required by the body [1]. Many of them also contain fibre and several disorders, such as heart disease, constipation, diverticulosis and diabetes have been associated with low-fibre diets. The Dietary Reference Intake for fibre is 38 and 25 g/day for young men and women, respectively, based on the intake level observed to protect against coronary heart disease [5].

Simple carbs, despite their bad rep, are a great way to refuel energy quickly during or after competition.

So approach diets that significantly reduce carbohydrates with caution, especially if you are engaged in a physical training programme – which every healthy individual should be. If you need to lose weight, don’t see carbs as the bad guys. You should decrease your calories gradually and increase your physical activity. Choose fibre-rich carbohydrate foods and avoid added sugars. Making healthy carbohydrate choices while reducing calories and increasing physical activity is the healthiest path to weight loss.

  1. World Health Organisation (1998). Obesity: preventing and managing the global epidemic. WHO: Geneva.
  2. Gibney, M. J., Lanham-New, S. A., Cassidy, A. & Vorster, H. H. (2009). Introduction to Human Nutrition; 2nd West Sussex: Wiley-Blackwell.
  3. Diabetes: The global diabetes community. (taken on 06/12/2015)
  4. Food Standards Agency (2007). I FSA nutrient and food based guidelines for UK institutions.
  5. Beachle, T. R. & Earle, R. W. (2008). The Essentials of Strength Training and Conditioning: 3rd Human Kinetics: Champaign, IL.
  6. Maher, F., Vanucci, S. J. & Simpson, I. A. (1994). Glucose transporter proteins in brain. The FASEB Journal, 8, 1003-1011.

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