This depends on the type of cardio, duration of the exercise, at what time you're exercising and your primary goal. To fuel yourself well, eat some fruits or simple proteins 30-90 mins before cardio. Cardio late in the day doesn't require food as you will use body fat to fuel through. Eat depending on if you want to burn fat or gain muscle.
If you are reading up on how to design a proper workout and nutrition program, you’ve likely come across some information regarding how to eat before strength training. Strength training demands certain types of fuel from the body and if you aren’t eating as you should be, it’s going to significantly hinder your performance.
But, what about cardio training? How should you be eating before it? There’s been much confusion over the past decade-plus as to how to eat (or not to eat) before aerobic exercise. Let’s look at a few of the determining factors that need to be considered so that you can make sure you are feeding (or not feeding) sufficiently beforehand.
Factor #1: The Type Of Cardio
First, you need to consider the type of cardio that you are doing. If it’s intense interval training, you would treat it much the same way as you would a strength training workout session. Your body is going to need some carbohydrates for glucose along with some lean proteins about 30-90 minutes beforehand. If you are using a fast acting protein (such as a whey protein shake) with a serving of fruit, you can get away with as little as 30 minutes beforehand. If you’re eating some animal protein with a complex carb source, you’ll want to push it further towards the 90 minute mark.
If it’s just a steady state cardio workout, then what you eat is less important and instead, your body can utilize fat as a fuel source. This is one reason many people do fasted cardio training – it’ll allow them to tap into their body fat stores more quickly.
Factor #2: The Duration Of Cardio
Second, you should also take into account the duration of your cardio training. If you are planning on doing a long endurance session, even if it is just moderate intensity, you may want to eat beforehand or pack a shake to sip on while doing the session itself. This is most applicable for those training for endurance events who will be exercising for longer than an hour at a time. You need to make sure that you are giving your body enough fuel to get through those sessions.
Factor #3: What Time of Day You Are Performing Your Cardio
If you are doing your cardio later in the day, whether high-intensity or not, you may not have to worry about a specific “pre-workout” feeding as you will have given yourself sufficient fuel from your previous meals throughout the day. If you have eaten a regular meal or snack within 2-3 hours of performing your cardio, you may not need a pre-feed at all. If you are doing cardio first-thing when you wake in the morning, you will definitely want to weigh your options. High Intensity cardio will definitely demand a feeding (as referenced in Tip #1 above).
If doing steady-state (such as a 30 minute+ walk), you may be able to get up and go. Some may need a cup of coffee to get them going (caffeine actually helps release fat lipids for fuel, too). Others may want to have a scoop of protein powder or, at least, a serving of Branched Chain Amino Acids (BCAA) to help keep any burning of muscle tissue as fuel to a minimum.
Factor #4: Your Primary Goal
Finally, also take into account your goals. If weight loss is the goal, you won’t feed as much before any form of cardio training as if muscle building was the goal. If you are building muscle, you should be minimizing your cardio anyway so as to not have it interfere with the muscle building process.
So there you have some key tips and points to know and remember about your before-cardio menu. Make sure that you are giving it the attention it deserves.