Is breakfast really the most important meal of the day? If you are not hungry in the morning or simply cannot find the time, is training in a fasted state going to impair your performance in the gym?
Let’s take a look.
Breaking down fasted exercise
As the name would suggest, fasted exercise is simply performing exercise in a fasted state, this is typically done upon waking before breakfast is consumed. By skipping breakfast, you are likely to have lower carbohydrate stores (known as glycogen stores) than if you were to consume a carbohydrate rich meal. But what does this actually mean? Well, the influential role of carbohydrates on endurance performance has been well documented for some time (1), with lower glycogen stores being strongly associated with decrements in performance (2). However, is this the case for resistance exercise?
What does the research say?
Unfortunately, there have been very few studies conducted in this area. The majority of research conducted on carbohydrate consumption has focused on endurance or intermittent exercise, with very little of the literature examining the effect on short duration resistance exercise. However, there is still plenty of research examining the energy systems involved in resistance exercise, so by evaluating this data, it may offer us insight into how skipping breakfast and therefore training in a low glycogen state may affect performance.
For instance, it is well established that resistance exercise heavily relies on utilising the anaerobic pathway to meet energy demands (3), which happens to be extremely reliant on carbohydrates in the form of glucose (the molecule it gets broken into). Therefore, it could be argued that there is likely to be a reduction in performance if an individual is not optimising their carbohydrate intake during breakfast. However, Mitchell et al. would suggest otherwise. The authors examined the effect of pre-exercise carbohydrate status on resistance exercise performance. They did this by having participants perform numerous resistance based exercises to failure following either a low or high carbohydrate diet. There were no differences found between the two groups, suggesting that pre-exercise carbohydrate status was not a limiting factor for resistance exercise performance of short duration (4).
What did we do?
The current recommendations suggest for exercise lasting less than 45 minutes, carbohydrate ingestion is not required, and will not lead to an improvement in performance (5). To delve further into this, we conducted a study to examine the effect that pre-exercise carbohydrate feeding had on morning resistance training performance. In order to do this, we had nine resistance trained subjects brought into a lab to perform numerous sets on the bench press under either a fed or fasted state, they were well and truly pushed to their limits.
Prior to testing, the subjects were required to turn up in a fasted state in addition to having not drank alcohol or performed strenuous exercise within the 24 hours before. Blood samples were taken to measure blood glucose concentrations and the subjects perceived hunger and thirst was recorded. 45 minutes before the resistance exercise testing commenced, the subjects consumed a flavour matched breakfast drink containing either 0g of carbohydrates (placebo trial) or 1.5g of carbohydrate (carbohydrate trial) per kg body mass with a 20% carbohydrate solution that would provide 200g of carbohydrates for every 1litre of fluid, the subjects consumed 5ml of energy free orange squash per kg body mass. It is important to note that the subjects were unaware of which drink they were consuming to remove any placebo effect that may have occurred.
Each subject completed one practice run of the trial followed by two experimental trials, each on separate days with two weeks between to ensure they were fully recovered. On the two experimental trials, the subjects consumed either the placebo or carbohydrate drink, alternating the drink they had on the first trial to the next. This was done in a randomised counterbalanced fashion, meaning all subjects completed the experiment in a random order and consumed both drinks on separate occasions.
In terms of the resistance exercise performed, on each of the experimental trials the subjects completed a total of 8 sets on the bench press, lifting 90% of their 10-rep max which was previously identified before the preliminary trial. To ensure both trials were completed evenly, exercise performed was equivalent in terms of number of total sets complete and the rest period in between was accurately timed. This can be seen in Table 1.
Table 1: Bench Press Testing Protocol
To further examine the effect of breakfast was having, we had the subjects provide us with a Rating of Perceived Exertion (RPE) using the 15-point Borg RPE scale as shown in Table 2. This was a simple method employed to gain an understanding of how hard the subjects thought they were working during each set to failure (sets 6-8). Additionally, the subjects hunger levels were taken following ingestion of either the placebo or carbohydrate drink.
Table 2: Rate of Perceived Exertion.
What did we find?
The results revealed that despite the number of repetitions complete in each set decreasing as more sets were performed, there was no difference between the two trials. Both trials had a similar decrease in repetitions performed in addition to the total numbers of repetitions complete across all three sets, as displayed in Figure 1.
Figure 1: Mean number of repetitions complete across all three sets. (n=9)
Similarly, although RPE increased over the number of sets performed, subject’s responses were similar between both trials and the mean RPE across all three sets was no different between the placebo and carbohydrate trial. One notable difference was that following the ingestion of the carbohydrate breakfast drink, hunger was reduced indicating the subjects we in a more satiated state, however, as shown this did not impact on performance.
What did we conclude from this?
To summarise the findings, resistance exercise performance was not improved by consuming a carbohydrate rich breakfast in the form of a drink. The study supports previously highlighted literature in suggesting that ingestion of carbohydrates prior to resistance exercise will not improve performance. A potential reason for this may be the bench press exercise could have predominantly relied on the phosphocreatine energy system which may not be limited by carbohydrate status. Additionally, it could be speculated that the subjects completing the study in a fasted state still had adequate glycogen stores from their dietary intake consumed the day before.
From a practical perspective, the evidence would suggest that regardless of whether you wish to consume breakfast or not in the morning, it will have no effect on your performance. Therefore, nutritional recommendations for individuals performing resistance exercise in the morning should be based on personal preferences to meet their needs.
1. Jeukendrup A. Carbohydrate intake during exercise and performance. Nutrition 2004;20(7-8):669-677.
2. Burke L, Ross M, Garvican-Lewis L, Welvaert M, Heikura I, Forbes S et al. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. The Journal of Physiology. 2017;595(9):2785-2807.
3. Vianna J, Lima J, Saavedra F, Reis V. Aerobic and Anaerobic Energy During Resistance Exercise at 80% 1RM. Journal of Human Kinetics. 2011;29A(Special Issue).
4. Mitchell J, DiLauro P, Pizza F, Cavender D. The Effect of Preexercise Carbohydrate Status on Resistance Exercise Performance. International Journal of Sport Nutrition. 1997;7(3):185-196.
5. Burke L, Hawley J, Wong S, Jeukendrup A. Carbohydrates for training and competition. Journal of Sports Sciences. 2011;29(sup1):S17-S27.