Top Ten Diet Fallacies:
Eating before Exercising
By Ori Hofmekler
Author of The Warrior Diet: Switch on Your Biological Powerhouse For High Energy, Explosive Strength, and a Leaner, Harder Body
Many people assume that the human body operates like a machine and therefore in order to work, it needs to be fueled like a machine. Eating before exercise seems to make sense. But does it really?
As you'll soon realize, the idea that pre-exercise meals provide the muscle with instant energy is literally wrong, often misleading and counter effective. In order to provide the muscle with nutrients and energy, food must be first fully digested.
During digestion food is broken down into smaller compounds, yielding molecules of amino acids, fatty acids and glucose – which are transferred to the body's tissues through the circulatory system. The digestion elimination process, that occurs in the stomach, intestines, liver and kidneys, respectively, requires substantial amounts of energy. During digestion, blood flow shifts from the brain and muscles to the inside organs (responsible for digestion and elimination). That shift in the blood flow profoundly affects the brain and muscle tissues, lowing their capacity to perform and resist fatigue.
The question remains: "What about meals that require almost no digestion?" such as those made from fast assimilating nutrients. (Note that fat is a slow digested and assimilated nutrient compared to protein and carbs.)
Consuming a pre-exercise meal made from a blend of fast releasing proteins and carbs (such as whey and sugar), looks initially quite appealing. In theory such meals would nourish the muscle tissues with amino acids and glucose to inhibit muscle breakdown, while providing instant energy. It all makes sense, but even so, in real life, things often work differently than in theory.
Recent studies demonstrated that eating fast releasing foods before or during exercise could be counter effective, to say the least. Investigators in the school of sport and exercise science, University of Birmingham, Edgbastion, England found that ingestion of carbs before exercise adversely elevated plasma cortisol levels.
Interestingly enough, there was a significant reduction in post exercise cortisol when carbs were not ingested before exercise. Furthermore, there was a faster shift from carb to fat fueling during exercise, when a pre-exercise meal was not applied. As for protein, what failed to reach mainstream nutrition knowledge is the already established fact that protein rich foods raise cortisol levels if applied incorrectly.
Studies at the University of Lubeck, in Germany, found that oral administration of fast releasing protein foods such as hydrolyzed (pre-digested) proteins, have an even more profound cortisol elevating effect, compared to whole protein foods. Note that chronic elevated cortisol has been associated with muscle wasting and fat gain (in particular abdominal fat.)
In summary, pre-exercise meals may rob the brain and muscle of energy (due to digestion). Eliminating the digestion effect of pre-exercise meals may only make things worse. Eating meals made from fast releasing proteins and cabs, before exercise, can cause a profound cortisol elevating effect during and after exercise. This may severely compromise ones ability to build muscle and burn fat.
In conclusion, DO NOT EAT before exercise, instead eat right after exercise. Ironically, the same meal that would be counter-effective before exercise can be most effective and beneficial when applied after exercise.
Numerous studies have demonstrated the critical positive effects of post-exercise recovery meals on total muscle recuperation (i.e. replenishment of energy reserves and increased protein synthesis). Recent studies at the University of Texas Medical Branch, in Galveston, TX, revealed that applying fast releasing proteins and carbs after exercise had substantial anabolic effect on stimulating net muscle protein synthesis, even in cases of elevated cortisol.
Consequently, we are not preprogrammed to be fueled like machines. Our biological machine is based on survival mechanisms that when triggered, increase our capacity to utilize fuel, generate energy and better survive. We trigger these mechanisms, when we follow cycles that rotate between undereating while in an action followed by eating while in rest. For the human body, timing affects everything. "It is when you eat that makes what you eat matter."
How to Apply Pre-Exercise Meals
You can successfully apply pre-exercise meals without the typical adverse effects (increased metabolic stress and elevated cortisol) by incorporating the following tips: Such meals should consist of small amount of protein or carbs coming from easy to digest, light fresh food sources such as poached eggs yogurt or whey protein (up to 20g) or low glycemic fruits (apples, berries, and papaya), one fruit or one bowl of fruit per meal. (You should separate between protein meals and fruit meals.)
Pre-exercise protein meals should have a higher ratio of protein/carbs or fat than post-exercise recovery meals, to minimize insulin spike and reduce digestion time before exercise, respectively. Pre-exercise protein meals, to be fully digested, should be consumed up to a couple of hours before exercise.
Nevertheless, very small amount of fruits (1/2 of a bowl) or up to 10g of whey protein could be applied up to one hour before exercise. Note that the best time for energy loading isn't before exercise but in the first 30 minutes after exercise. Replenishment of energy reserves in the muscle reaches a peak potential via your post-exercise recovery meal.
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