Nutritional Timing, Training in a fasted state: Endurance Training

Nutritional Timing, Part I
Training in a fasted state: Endurance Training
- Should I eat in the morning if I want to burn Fat during my run?

Many of us have a Love-Hate relationship as it relates to Morning Cardio, mainly because of 2 reasons.

1) Phrases as “Rise and Grind” and “Hard work does not sleep” do not always sound as motivating when the alarm rings at 5am.

2) If you did not have a late snack or dinner the night before, you might be starving once you get yourself out of bed.

Problem number 1 has a quick fix, very much related to the “Suck It Up” principle. Problem number 2 is different story. If you manage to drag yourself out of bed, you might apply the “Suck It Up” principle once more and not allow yourself to eat because you want your body to burn FAT, and we all know that you can’t burn fat unless you complete the run in a “Fasting State”, or…
The belief that training in a fasted state would increase lipolysis (fancy word for breaking down fat to fuel your body) is largely based on two things:

·       The hormones that triggers fat breakdown increases during fasting. 

·       The body is low on carbohydrate storage (our other storage for energy) which means that the body would need to use fat as the primary energy source [1] [2].

When training at low to moderate intensity, the majority of your energy will come from fat.  In fasting state, even greater contribution will come from fat since you don’t have anything else in your body that easily can be used as an energy source.

Difference factors to take into account when discussing training in fasting versus fed state is individual training status, intensity and duration, and acute versus direct effect of the work out. The amount of fat used during fasting state will vary depending on training status. Trained individuals tend to use more fat during over-night fasted state compared to untrained individuals when matched for intensity[3].

It is commonly believed that over-night fast and low carbohydrate stores will lead to compromised performance. Research shows that training in fasted state does not lead to as great of a decline in performance as one might think. Relying on fat for energy has actually shown improved and maintained performance (amount of oxygen uptake, power output, tested times to exhaustion) after high and low intensity endurance training[4] ^[5] [6]. This is because when forced to, the body will enhance its use of fat as a source of energy. Using more fat will save and increase carbohydrate stores⁴. 

A lot of studies related to fasting have been conducted over Ramadan, and it is repeatedly emphasized that focus in cases like this should be on overall fluid and caloric intake rather than the timing of nutrients5. Even though main training objective during specific circumstance like this tends to shift towards maintenance and not optimization of performance, it should be said that some athletes do experience performance decrements during this time. A lot of the performance decrements are said to be related to subjective feelings of fatigue which will add additional stress to the athlete[7].

However, when looking at acute effects of training, the amount of fat used to fuel a work out after breakfast is less but the total daily fat expenditure is greater compared to fat expenditure following a fasted work out. The same relationship is true related to the total amount of calories needed for the entire day[8].

So if you are looking to lose weight and decrease your fat percentage, maybe adding a light breakfast before your morning jog would be beneficial. In contrast, if you are struggling with eating in the morning or would like to hit the snooze button one more time instead of making breakfast before your morning jog, it is okay as long as you feel good throughout your training.

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[1] Binzen, C. A., Swan, P.D., &Manore, M.M. Post exercise oxygen consumption and substrate use after resistance exercise in women. Medicine and Science in Sports and exercise, 33 (6), 932-938 (2001)

[2] Kovisto, V.A., harkonen, M., Karonen, S.L., Groop, P.H., Elovainonio, R., Defronzo, R.a. Glycogen depletion during prolonged exercise: Influence of glucose, fructose, or placebo. Journal of Applied Physiology, 106 (6), 2026-2039 (1985)

[3] Bergman, B.C., &Brooks, G.A. Respiratory gas-exchange ratios during graded exercise in fed and fasted trained and untrained men. Journal of Applied Physiology, 86 (2), 479-487 (1999)

[4] Aziz, A. R., Slater, G.J., Chia, M.Y.H., The, K.C., Effects of Ramadan fasting on training induced adaptations to a seven-week high-intensity interval exercise programme. Science of Sports, 27, 31-38 (2012)

[5] Stannard, S.R., Buckley, A.J., Edge, J.A., Thompson, M.W. Adaptations to skeletal muscle with endurance exercise training in the acutely fed versus overnight-fasted state. Journal of Science and Medicine in Sport. 13, 465-469 (2010)

[6] Jeukendrup, A.E., Killer, S.C., The Myths Surrounding Pre-Exercise Carbohydrate Feeding. Annals of Nutrition and Metabolism. 57(2) 18-25 (2010)

[7] Chaouachi, A., Leiper, J.B., Souissi, N., Coutts, A.J., Chamari, K. Effect of Ramadan intermittent Fasting on Sports Performance and Training: A Review. International Journal of Sports Physiology and Performance. 4, 419-434 (2009)

[8] Paoli, A., Marcolin, F.Z., Neri, M. , Sivieri, A., Pacelli, W.F. Exercicing fasting or Fed to Enhance fat Loss? Influence of Food Intake on Respiratory ratio and Excess Postexercise Oxygen Consumption After a Bout of Endurance Training. International Journal of Sport Nutrition and Exercise Metabolism. 21, 48-54 (2011)