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When I first started as a personal trainer back in 2013 a trend in low/no carb (carbohydrate) diets was in full swing. Celebrities, trainers and even some scientists were promoting these diets as the fix to everyone’s health problems, especially weight loss. People that I would talk to in the gym including my own clients, would often tell me they don’t eat carbs because they are bad for you.

This is where the misunderstanding begins, carbohydrates are not bad for you! As human beings, we have consumed carbohydrates since the dawn of time and are an essential part of our diet. The problem arises with the types of carbohydrates we are now mainly consuming and the quantities.

There are two main categories of carbohydrates: simple and complex. Simple contain no more than 10 sugar units whereas complex contain many more than ten, which can be arranged straight, branched or coiled. As you can see simple and complex contain sugar complexes but it is the difference in composition and structure that determine how they interact with our digestive system.

Which Type of Carbohydrate Should I be Eating?

To maintain a healthy balanced diet the majority of your intake should come from eating unprocessed complex carbohydrates. Foods containing this type will often be the most nutrient-dense, containing not just energy but also fibre, vitamins and minerals. Examples of good unprocessed complex carbohydrate sources include:

  • Potatoes
  • Wholegrain rice
  • Wholegrain pasta
  • Beans
  • Oats
  • Broccoli
  • Carrots

This doesn’t mean you should shun foods containing mainly simple sugars. Unprocessed foods such as oranges, grapes and milk contain large amounts of simple sugars, yet they also contain many essential vitamins and minerals.

Carbohydrates to Avoid

It’s the processed foods that have given carbohydrates such a bad reputation. Food manufacturers are aware that certain simple sugars can give us a sense of euphoria when consumed. Knowing this they create food items that are packed full of simple sugars but have no added nutritional benefit. For example, an orange contains a lot of simple sugars but also contains B vitamins, fibre, potassium, calcium and of course Vitamin C. A processed chocolate bar on the other hand just contains sugar, which is just pure energy.

Carbohydrates for Health

Both unprocessed simple and complex carbohydrates are an essential part of our diet. They provide us with an essential source of glucose that many bodily functions rely on. Yes, glucose can be synthesized from fat and protein, but for a physically active person, these pathways are limited. As well as energy they provide us with essential fibre and nutrients. Fibre not only aids digestion but feeds our gut bacteria. Many natural foods containing mainly carbohydrates also contain a plentiful supply of vitamins and minerals, again essential for our health.

Carbohydrates for Fitness

When it comes to performing medium to intense exercise an adequate supply of glucose is essential to power our muscles. Without a good constant supply, performance will be drastically reduced. This is because although fat is a dense source of energy it cannot provide energy quick enough, the process is just too slow. On the other hand, energy derived from glucose is much quicker, able to provide quick efficient energy for all but the most intense exercise. The only downside to using glucose as a fuel is that the body can only store a limited amount as glycogen in the liver and muscle tissue. Once used up it needs to be replenished, and the best way to do that is by consuming high carbohydrate foods.

change in fuel utilisation carbohydrate chart

Figure 1: The change in fuel utilisation at three different cycling intensities.
As the exercise intensity increases fat utilisation decreases in favour of carbohydrate substrates (Loom, et al., 2001).


Carbohydrates are a key macronutrient that we should not be scared of consuming. They provide us with essential energy and fibre that keeps our body functioning correctly. Poor health is due to eating the wrong types of carbohydrates, the processed chocolate bars, cakes and crisps that only contain simple sugars with no other nutrients. If you are active, doing regular exercise, unprocessed carbohydrates are your friend not your enemy.


Alberts, B. et al., 2008. Molecular Biology of The Cell. 5 ed. New York: Garland Science.

Barasi, M. E., 2003. Human Nutrition a Health Perspective. 2 ed. London : Hodder Arnald .

Lanham-New, S. A., Stear, S. J., Shirreffs, S. M. & Collins, A. L., 2011. Sport and Exercise Nutrition. 1 ed. Chichester: Wiley-Blackwell.

Loom, L. J. C. v. et al., 2001. The effects of increasing exercise intensity on muscle fuel utilisation in humans. The journal of physiology , 536(1), pp. 295-304.

McArdle, W. D., Katch, F. I. & Katch, V. L., 2010. Exercise Physiology Nutrition, Energy and Human Performance. 7 ed. Baltimore: Lippincott Williams and Wilkins.

Matt Sills