We get asked a lot whether or not our cardio should be fasted or fed. It's an excellent question. The reason it comes up is that there is some small amount of research that showed fasted cardio is better for weight loss.
Let's defined the terms. Fasted cardio refers to doing long slow distance cardio before having any food for the day. Many people who do this will still have beverages prior to the cardio such as water or tea or even coffee. Felt cardio refers to consuming some food before you do your cardio. This can be a meal an hour or two before exercising or even a snack just before hitting
the bike.
I will mention there can be some risk in doing fasted cardio. There's more potential for lightheadedness, dips in blood sugar and cramping. Watch out for those. It is absolutely not some thing recommended for those who are insulin-dependent diabetic's. Before embarking a plan that includes fasted cardio consult your medical provider. Or me :)
Here we go - The answer to our question really depends on what your goal is. And by goal I mean the goal for the work out. I'll explain a little more later.
Fasted or Fed Cardio:
Here's how I break it down – if you are trying to burn fat during this work out exclusively then I believe fasted cardio can be a good choice. This means you've achieved a healthy muscle mass and you're looking to just shed a few extra pounds of pure fat. You have a good resting metabolic rate, you've got excellent control of your diet and good dietary habits and all you need to
do is spend an hour burning fat. This is a good time for fasted cardio in my books.
If you were still working on getting fitter, if your metabolic rate isn't adequate and you need a boost if your muscle mass is still a bit low then fed cardio makes more sense. When you do fed cardio you burn more calories quicker so the workout is more efficient and you get an after burn so you've got an increase in calorie burn for the remainder of the day.
These after effects can be very helpful for improving weight loss.
I hope that clarifies my thinking on fed versus fasted cardio. I personally do a mix of both but since my workout time is in the evening or afternoon my fasted cardio is only after a five hour fast. That seems to be suitable to me. There is individual variability here.
Dr. David Duizer ND