What should we eat before a workout? This question has long been debated in the fitness industry. Is giving your body fuel before exercise really what your body needs to perform its best? Does going without food before exercise inhibit our ability to perform? Is sugar really the best form of fuel to burn during exercise? Let’s take a look at these questions below and shine some scientific research light on these areas of debate.
1. Shunting of Blood
During exercise, our body moves blood towards areas performing work. For example, when running, blood moves to our muscles that need more oxygen to fuel energy production. The body will shut blood to these highly metabolizing areas and vital organs such as the brain as demand increases, and away from non-vital organs like your stomach, GI tract, liver, pancreas, and kidneys. This allows us to prioritize oxygen availability to important areas needed for athletic performance. The opposite happens when we are eating and digesting. Our body shunts blood away from our muscles and moves it to the stomach and GI tract in order to fuel digestion and assist with the absorption of nutrients into the circulatory system. This can be one of the contributing factors to fatigue following a big meal as blood is shunted away from our brain towards our stomach – we experience fatigue or sleepiness.
When you have eaten before exercise, your body is busy churning the stomach, creating movement through the GI tract, making enzymes, releasing digestive juices, absorbing nutrients and distributing them for utilization. If you start a workout in the middle of this process, the body needs to stop digestion and divert blood back to your muscles to provide more oxygen. Less blood is then available to move to these important areas, our muscles tire quickly, we can feel nausea and fatigue from having exercise hormones triggered while attempting to digest. This is the reason our parents told us when we were kids not to go swimming after eating.
The same is true when we sleep. Blood is shunted towards areas of the body that need rebuilding, recovery, and cleaning – particularly the brain. This is why sleep is so important; this is when maintenance and cleaning occur, helping organs function optimally during the day. Metabolites from energy production in the brain need to be cleaned out and recycled after a long day of thinking. When we eat before bed, we stimulate digestive enzymes, hormones, and blood supply back to the stomach and GI tract, taking time, energy and resources away from our maintenance and recovery phase. This is one factor that contributes to some waking up feeling unrested. Some may even feel slightly hungover after eating a late-night snack because they are deprived of quality sleep. This process is even more important for those who are active during the day because they have higher recovery requirements. Additionally, our organs function on circadian rhythms as much as our brain does. Asking the pancreas to produce insulin and digestive enzymes later at night can cause production issues over time. Tending to our body’s natural circadian rhythms is one of the many reasons time-restricted eating is beneficial for human health and longevity.
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2. The Autonomic Nervous System
Similar to the cardiovascular system, the nervous system receives mixed signals when eating before exercise, causing more biological confusion.
The nervous system has two opposing branches that send signals to and from the brain to stimulate activity (sympathetic) or rest and recovery (parasympathetic). These systems are commonly referred to as our “fight-or-flight” and “rest-and-digest” systems. Parasympathetic stimulation occurs when you eat a meal – our brain receives signals from the gut, blood rushes to your stomach, our body goes into relaxation and cellular repair mode. Parasympathetic stimulation decreases activation of the sympathetic system, which inhibits the secretion of hormones associated with “fight-or-flight” or stress, and increase digestive hormones and enzymes secretion. This is one of the reasons why we feel calm and happy following a meal – our hormones signal our cells, telling them that it’s all good, no need to be stressed, we have fuel to survive another day.
Given this, we can see the issues that arise when eating directly before exercise. Our body is in parasympathetic rest and digest mode, then all of a sudden, there is a surge in sympathetic stimulation brought on by your workout. Sympathetic hormones like adrenaline and cortisol shoot up in order to prepare the body for activity, leaving us with opposing commands being activated. Digestion is halted as the body becomes sidetracked with energy production and adrenaline stimulation. Sympathetic stress hormones released cause temporary insulin resistance that blocks the body’s ability to utilize glucose effectively in the bloodstream until a more appropriate time to digest comes along.
3. Metabolic Flexibility
For those of you who are thinking, “nope, I have to eat before a workout, I get dizzy or lack energy etc.” The information below is for you.
I see this all the time; people are reaching for an “energy boost” or pre-workout before exercise (aka sugar) or reach for sugar-filled gums/jells during a soccer game. Our bodies are genetically programmed to be able to fast for days if food is not around – it actually thrives in these conditions. Cognitive function improves, our cells start recycling old ineffective cells (autophagy) and our genetics are forced to adapt to new environmental stressors (epigenetics). These intermittent bouts of stress signal our cells to perform better. Therefore, the body responds by making changes to enhance performance in order for our species to survive and reproduce (this is the ultimate goal of all living things). Optimized cognitive function during hunger was imperative evolutionarily, helping humans use their intelligence to find food. So why then are some people not able to make it 2 hours without a snack these days? Or feeling dizzy after 5 mins of cardio on an empty stomach when evolutionarily, humans had empty stomachs for days or weeks at a time?
It’s because we’ve conditioned our cells to behave this way. We have been eating every 2-4 hours since we were young, with multiple snacks between meals. Our bodies have adapted to this way of living, expecting scheduled doses of sugar throughout the day. As the evolutionary saying goes – if you don’t use it, you lose it. That’s exactly what happened here. This is our body’s response to its environment. People who eat 3-6 meals a day that are low-fat and high-carb are giving their cells a steady dose of glucose so that their cells never have to switch into fasting mode, which utilizes stored fat for fuel instead of glucose. Continuous intake of food such as snacking throughout the day actually increases our appetite, stimulating insulin production (& fat storage) throughout the day and suppressing autophagy. When our bodies expect regular glucose throughout the day; when we don’t get it, we feel hangry, light-headed, fatigued, and have an overall lack of energy. This stimulates sugar cravings to seek out new energy in the form of glucose, making us feel temporarily better for another 2-3 hours until our blood sugar dips again and we crave more sugar. Does that sound fun to you? This is called a blood sugar roller-coaster – this is exactly what we aim to prevent to improve health and wellness.
So how do we reverse this pattern? By reintroducing fasting to our cells. Utilizing time-restricted eating and improving diet quality allows us to turn those sleepy glucose-burning cells back into hybridized fat-burning cells. Add in high-quality whole foods that won’t spike blood sugar and say adios to sugar cravings and fatigue. You will be full of energy powered by proper nutrition and will enjoy the effects of stabilized hormones and mood. Now that sounds like a much better way to live to me. If you are pre-diabetic or diabetic – fasting is the fastest and most effective way to decrease your fasting blood sugar and hemoglobin A1C levels, allowing you to steadily decrease and eliminate the need for diabetic medications (type II DM). Working out while fasting quickly tells the body to start using stored fat for fuel, helping to improve overall metabolic flexibility, allowing us to feel energized without brain fog and fatigue.
4. Oxidative Stress
Improving metabolic flexibility and using stored fat for fuel decreases the amount of oxidative free radicals produced by the body when compared to burning glucose during energy production (making ATP). This decreases inflammation throughout the body and protects proteins and DNA from damage by these rogue electrically charged ions. This means our body needs fewer antioxidants in order to keep this oxidant vs anti-oxidant battle in balance, helping maintain a healthy homeostatic threshold. Less oxidative stress post-workout means less recovery time needed and improved overall longevity. This means inflammation will return to baseline quicker and our body will need less recovery time between workouts, making you stronger and fitter, faster.
For full details about the many benefits of including time-restricted eating or fasting into your routine, check out our Circadian Synced Wellness guide. For details on improving the quality of our diet, see our Nutrition Guide.
As always, we would love to hear your feedback. Let us know in the contact section or email us at lolohealthco@gmail.com or see our COACHING page for assistance in executing this information.