How long before your workout begins is critical because you could eat some heavy (high in fats and or protein) food that is still undigested and sitting in your tummy. That’s OK, if it is an easy aerobic, low intense workout. But if it is a high intense weight training or aerobic workout – it can make your workout more sluggish, and contribute to bloating, gas, indigestion or other digestive problems.
Certain foods take longer to digest than in home workout others. Fruits digest very quickly. On average they pass through your digestive system in 30-45 minutes. Proteins and fats take about 2-3 hours to digest, so if you have plenty of time before a workout you can eat peanut butter and crackers, cheese or protein drink. But if you eat those types of foods, and I am not saying if they are good or bad to eat, but you need to look at how much time you can give your body to digest it before you start your workout, especially if it is going to be an intense workout.
Regarding to the intensity of your workout, the body perceives ‘intense exercise’ as being in the ‘Fight or Flight’ mode. This turns off your other system, the ‘Resting Digesting’ mode. They don’t function at the same time. The point is, if your workout is intense and you ate a meal or snack loaded with protein and fats you need to give your body enough time to digest those foods before you begin an intense workout. Otherwise the food will probably sit in your stomach and not be digested properly and more than likely not help you during your workout.
On the other hand, if you are going to perform a low intensity, aerobic workout – the food you eat and the length of time to digest it is not as important because a ‘true’ aerobic workout will not shut-down your digestive system. So in essence you can eat some fruit or something loaded with fats or protein… neither one is going to have an effect on your low intensity workout.
FYI… an aerobic workout should allow you to maintain a normal conversation. It should not be intense enough to alter your respiratory or digestive system. A common mistake is to perform an aerobic activity (jogging, cycling, swimming, aerobic dance, etc. ) at too high an intensity level that it ceases to be aerobic and is predominately an ‘anaerobic’ high intensity workout.
The longer your workout the more fuel (calories) you will need or burn. The intensity of your workout will determine if your body is burning carbohydrates and proteins (lean muscle) for fuel or stored body fats. Aerobic exercise allows you to burn fats, whereas ‘anaerobic’ exercise will make carbohydrates and proteins your fuel source.
Therefore, if you are performing a long, low intensity aerobic workout… you can eat fruits, proteins or fats. Your body will be able to burn any of those fuels. But if it is a grueling, long, anaerobic workout your body will first burn up all the available carbohydrates and then protein. The fact that it is a purely ‘anaerobic’ workout will inhibit your body from burning stored body fats for fuel, so make sure you have loaded up with enough carbs before your workout, otherwise you will start breaking down lean muscle… which is the last fuel source you want to be using to get through a workout.
As you can see, there is not a simple cookbook answer… you have to consider those variable and understand you may or may not want to eat the same thing before two completely different types of workout. A rule of thumb to follow is if your workout causes you to start burping or gets you bloated and gassy, chances are it’s not the right pre-meal workout for you.