Breaking the Fast, Cardio & Your Brain: Cardio on Empty is Fatiguing. Fasting Without Exercise, However, is Nootropic

Boking: Every endurance athletes knows and fears it, so wouldn't just that happen when you do your cardio on empty in the morning? And what about the effects on your brain power? Will your gray matter bonk, as well? And if so, what can be done about it?

Today's SuppVersity post is a little different from the usual "Training on empty? Yes / No / Maybe!" debate that flares up every now and then on almost every fitness related bulletin board of the World Wide Web. And in as much as I would like to say that this was all the credits belong to me, the fact that the the following dissertation may actually make a practically relevant contribution is due to the experimental design of the latest study from the Northumbria University in Newcastle, Tyne and Wear, in the UK (Veasey. 2013).

Why is that? Well, contrary to the majority of breakfast "yes or no" studies this one has both an exercise and and a cognitive performance aspect. Since I suppose that most of you are not living to train, but training to live, this is practically highly relevant. I mean, what's the use of "looking good naked" due to the purported benefits of working out "on empty" first thing in the morning if that reduces your cognitive performance in a way that you risk being fired?

Now that I've got everyone's attention, let's look at what exactly R.C Veasey and her colleagues did to find out whether having / not having breakfast before morning cardio or rest will impact cognitive performance and mood later in the morning. To this ends, the researchers recruited 12 healthy, active men in their early 20s with an average BMI of 24.5 ± 2.0 kg/m², who had to abstain from rigorous exercise and alcohol consumption prior to the exercise trials before they reported back to the lab after a 12h fast.

Do the online stroop testto get an idea of what the subjects in the study had to do and why it may in fact not be ideal to have breakfast when you are not exercising. After all, the results of the study at hand clearly suggest that the the accuracy in the stroop performance test decreases significantly in the "no exercise, but breakfast" condition.

"After confirming compliance to the study restrictions, a baseline completion of the cognitive tasks and mood scales was then undertaken, before participants were administered the test breakfast or remained fasted. During the 2 h rest period which followed, cognitive performance and mood were measured at 60 and 120 min. In between these periods, participants were allowed to read, write or watch a DVD. In the exercise trials (NB E and B E), participants then completed a treadmill run at 60% of their VO2, until 2.9MJ had been expended with heart rate and rate of perceived exertion (RPE) measured at 10 min intervals throughout. [...] On rest days (NB NE and B NE), participants rested for the equivalent amount of time. Cognitive performance and mood were reassessed before participants were administered a test drink, followed by a 90 min rest period where cognitive performance and mood was assessed at 30 and 75 min. This was followed by an ad libitum lunch where participants were asked to consume enough food to feel satisfied to a normal level. After lunch, they completed the cognitive tasks and mood scales for a final time and were then free to leave the laboratory." (Veasey. 2013)

"Hah?" Yeah, that was my initial reaction to the overcomplicated study protocol, but don't worry, after you've taken a peak at the following overview I guess, you will be able to identify how this corresponds to getting up, driving to the gym, working out and head to your working place with or without breakfast.

Illustration 1: Outline of the allegedly somewhat difficult to understand study protocol (Veasey. 2013)

You see? It's not so complicated as the scientists description of the protocol made it appear. Four conditions, total, two conditions with and two without 72g syrup flavor porridge oats with 360ml milk, each repeated twice with or without exercise after the initial rest period - that's all.

"Ok, whatever... what were the results? "

As the scientists had expected, the consuming breakfast prior to exercise did in fact elicit the most beneficial cognitive performance and mood effects following in the exercise conditions.

Figure 1: Cognitive performance, mental fatigue and tension in the four trials (Veasey. 2013)

The data in figure 1 does yet also reveal that having breakfast before rest had detrimental effects on the ability of the study participants' ability to rapidly process visual information and omitting breakfast improved their performance on Four Choice Reaction Time test.

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Bottom line: According to the results of the study at hand, you do have two options to maintain / optimize your "desk performance" (cognitive performance at the job) in the morning hours:

• either you fast and refrain from working out or
• you have breakfast and work out

It goes without saying that even minor changes in the protocol, e.g. the omission of the 120min rest period (I gather you don't need that long in the bathroom before you either leave the house and go for a jog, sit on your cycle ergometer or drive to the gym), for example could skew the results in a favorable way for the "non-breakfast condition", if  you don't stick to a meager 250ml of chocolate milk after your workout but indulge a real breakfast (see box on the right for a scientifically warranted suggestion)...

The latter is by the way a practice that has always worked pretty well for me. I did however have to realize that this does only work if you really eat and don't just down a protein, let alone whey shake that will only spike your insulin and send you down into the abyss of borderline hypoglycemia. A state which is certainly nothing your cognitive performance can benefit from (Lindgren. 1996).

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Highly suggested read: "Circadian Rhythmicity - "Breakfast" or "Breaking the Fast"? Fasting as Zeitgeber & All About King, Prince & Pauper" (read more)


References:

• Cooper SB, Bandelow S, Nute ML, Morris JG, Nevill ME. Breakfast glycaemic index and cognitive function in adolescent school children. Br J Nutr. 2012 Jun;107(12):1823-32. 
• Lindgren M, Eckert B, Stenberg G, Agardh CD. Restitution of neurophysiological functions, performance, and subjective symptoms after moderate insulin-induced hypoglycaemia in non-diabetic men. Diabet Med. 1996 Mar;13(3):218-25. 
• Micha R, Rogers PJ, Nelson M. The glycaemic potency of breakfast and cognitive function in school children. Eur J Clin Nutr. 2010 Sep;64(9):948-57.
• Sihvola N, Korpela R, Henelius A, Holm A, Huotilainen M, Müller K, Poussa T, Pettersson K, Turpeinen A, Peuhkuri K. Breakfast high in whey protein or carbohydrates improves coping with workload in healthy subjects. Br J Nutr. 2013 Apr 16:1-10.
• Veasey RC, Gonzalez JT, Kennedy DO, Haskell CF, Stevenson EJ. Breakfast consumption and exercise interact to affect cognitive performance and mood later in the day: a randomized controlled trial. Appetite. 2013 Apr 19.