Carbohydrates: Should We Just Go ‘Low Carb’?

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It is quite common for many people to avoid carbohydrates in their diet due to a multitude of reasons (such as reducing body fat percentage), but are they really that bad when taken in the correct ways, and are all carbohydrates classed the same?

As well as being the body’s main source of energy, carbohydrates play a vital role in recovery, athletic performance and reducing fatigue. With all this in mind, there’s an obvious reason why there is so much confusion over these nutrients.

Is a carb a carb?

Complex and simple carbs…

For many years carbohydrates were traditionally categorised into either simple or complex, based on the number of monosaccharide units linked together, as well as the total fibre content of the food. The general consensus was that simple carbohydrates would provide a rapid rise in blood sugar compared to complex carbohydrates.

But did you know that this doesn’t always hold true… A good example of this is with fructose. Here it is classed as a simple carbohydrate but because it is broken down in the liver before entering the blood it doesn’t actually give a rapid increase in blood sugar.

As a result, Glycemic Index (or commonly known as GI) was determined as a more suitable method of categorising carbohydrates – due to the fact that it takes into consideration the rate of absorption into the blood and subsequent effects on insulin levels.

Using the Glycemic Index (GI)

Glycemic Index (GI) is a measurement of a foods effect on blood glucose levels and was originally developed to help patients with diabetes to control their blood sugar levels. It later became a useful tool by athletes for performance and by the general public to control body fat levels.

Foods are usually classified as being high, moderate or low GI on a scale of 0-100. Higher GI carbohydrates are preferred for performance whereas lower GI are better for fat loss and general health and wellbeing.

  • High GI – above 70 (potato, white bread, bagels)
  • Moderate GI – 55 to 70 (basmati rice, oats, sweet potatoes)
  • Low GI – below 55 (beans, berries, quinoa, honey)

What is the best time to have carbs and what type is the best?

Pre Exercise

The late 1960’s saw the emergence of carbohydrate loading strategies for improving exercise performance – arrive in a high carbohydrate state, and ultimately have more energy available to perform better.

However, before jumping the gun here, it is important to consider the context of why you want to carb load and if the sport you are participating in requires you to be loaded or not. For example, resistance based training would not require the same level of fuelling compared to endurance events such as a marathon where the energy expenditure is greater. Current recommendations for optimal performance and pre carbohydrate feeding are explained below:

  • Carbohydrate loading preparing for events up to 90 min high intensity exercise – 7-12 g/kg body mass per 24 hours leading to the event.
  • Carbohydrate loading preparing for events greater than 90 min of sustained intermittent exercise –10-12 g/kg body mass per 24 hours for 2 days leading to the event.
  • Pre-event fuelling before high intensity exercise less than 60 min – 1-4g/kg body mass 1-4 h before exercise.
  • Pre fuelling for resistance based exercise – low GI carbs (1g/kg body weight) are preferred. If the goal is fat loss then lower carb is better.

During Exercise

Carbohydrate feeding during exercise can support glycogen resynthesis, improve motor function and enhance performance but the amount and type of carbs is, again, highly dependent on the type of exercise. Therefore, it is essential to find out what the goal of the exercise session or workout is beforehand.

  • Exercise less than 30 min – if the exercise duration is less than 30 minutes, there are no benefits of taking any additional carbohydrates.
  • Exercise 45-90 minutes – when exercise is ‘full-out’ e.g. a football match, performance will benefit with additional carbs. Research shows that even carbohydrate mouth rinse can improve performance.
  • Prolonged exercise – for exercise lasting 1-2 hours carbs have been shown to improve performance (30g / hr is sufficient). When duration increases it is recommended to increase the amount of carbs (60-90g / hr), as long as it doesn’t affect gastrointestinal distress. Greater carbohydrate oxidation can occur through mixes of different types of carbs (glucose + fructose / 2:1 ratio).
  • If the goal is fat loss during your sessions rather than performance, the recommendation is to avoid carbohydrates (particularly high GI).

Carbohydrates - Post Workout

Post Exercise

The use of carbs post workout can have huge effects on your outcome of recovery and performance. The first way is that carbs (particularly high GI) can stimulate an insulin response which in turn increases the amount of glucose taken up by your muscle cells. Here the muscle membranes are more permeable to glucose so they can take up more glucose than usual. With this in mind, it’s suggested to consume moderate to high GI foods in the first 2 hours post exercise to increase glycogen replenishment and then revert back to low GI foods 24 hrs post exercise.

Insulin also has a second major function in the body which makes it important for strength and conditioning. As well as facilitating the storage of glucose, insulin is ones of the body’s anabolic hormones – meaning once it binds with its receptors it will activate protein synthesis whilst also preventing protein breakdown. In other words, it has the ability to promote muscle growth and therefore, the control of insulin through dietary carbohydrate is extremely important following resistant training.

What can we take from this?

Carbohydrates are clearly an important part of the diet, particularly for energy and performance but it goes without saying that people should pay particular attention when looking at their carbohydrate intake across the day.

Carbohydrates differ from one another and the types, timing and amount of carbs around training and throughout the day should be carefully considered in order to maximise performance (either endurance or resistance based), reduce body fat and support general health.

Practical recommendations.

  • The majority of carbs for everyday consumption should come from low GI.
  • Try to avoid late night high GI snacks and choose low GI.
  • Base your pre, and intra exercise carb intake on the type, intensity and duration of the sport/exercise.
  • Focus on medium to high GI carbs immediately after endurance based training to optimise the replenishment of muscle glycogen.
  • Try to include medium to high GI foods immediately after resistance training to promote muscle protein synthesis and prevent muscle protein degradation – this should be with approximately 20g of high quality protein to maximise net protein synthesis.
  • If there is a need to lose body fat, ensure that most of the ingested carbs are low GI, especially during the evening when muscle and liver glycogen stores are likely to be full.


Steve has a Masters degree in Sports Physiology and works within the BULK POWDERS™ product team. His role includes all aspects of new product development, from recipe concept and formulation to website content and legislations.

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