Hello Warriors! I’ve had this post in my back pocket for a hot minute. The question of when to do cardio in relation to meals is one that I have been hearing a lot lately. So today, I’ve got a hot take on a hot topic.
Talking about fasted cardio is tricky because if you were to draw a Venn diagram of where nutrition and exercise science overlap, fasted cardio would be it. So, while this is not a discussion of macros, calories, nutrients, or the like, I want to start this post by reminding you that my training is in exercise science.
Many athletes, especially high-level athletes, take into account meal timing as part of their training. Take, for instance, a distance runner who is going to be doing a sprint repeat type workout. These workouts are very high intensity and require carbohydrate be in the system already to be effective. In this case, this athlete is going to want to consume a carbohydrate rich meal an hour or two before their workout in order to maximize the effects of said workout.
This is a super basic example, but I’m using this to illustrate my point that in this case, the timing of the meal affects the workout. If this athlete didn’t eat prior to this type of workout, I can guarantee that they’d be halfway through their sprints and hit the wall.
On the flip side of the spectrum, an athlete who is about to do an offseason hypertrophy lifting session may choose differently. While lifting heavy weights is an intense activity, typically these are very short bouts and the fuel necessary to complete the activity comes from creatine that is stored in the muscle cells. Here, the athlete might choose nothing or something very light prior to the workout and a protein rich meal after.
Again, the point here is that the meal timing is meant to maximize the workout and the gains (pun intended). As it can be uncomfortable to lift on a full tummy, having a meal might be detrimental in this case.
But let’s call a spade a spade here. Most of us are not elite level athletes. The idea of fasted cardio emerged because weight loss is a goal that many exercisers happen to have. And the question became if cardio exercise is completed without a meal prior (i.e. there is a lower level of blood glucose to fuel the activity) will that promote burning stored body fat?
In so much of the debate in the media, this question is forgotten. The fact of the matter is that doing a certain cardio exercise for a certain amount of time at a certain pace or intensity is going to burn the same amount of calories whether you have a meal prior or not. In other words, if you walk for a half an hour at a 4 mph pace, that exercise requires the same number of calories from your body regardless of if you have eaten.
The question is really if the calories are coming from the glucose circulating in the body or from your body fat stores. The thought is that by doing fasted cardio, you’ll force your body to turn to body fat for the energy thus increasing fat loss. But the literature doesn’t back that up. In fact, the findings can be described as mixed, at best.
While some studies do find that fasted cardio results in more fat loss, others don’t. And some are even finding that fasted cardio results in consuming more calories later in the day to replace energy stores. Meaning that even though you may burn body fat during exercise, you are replacing those calories later. It never hurts to remember that the body is an amazing thing that wants to stay as it is.
Another monkey wrench in the debate is the intensity of cardiovascular exercise. If you are planning on doing some HIIT work or something more intense, just like my first example, you’ll need some fuel otherwise you won’t be finishing your workout. Or you won’t be feeling well. This type of work requires that your body produce the energy too quickly to rely on fat stores. If you are going for a walk, however, you might be able to rely on fat stores because your body doesn’t need as much fuel as quickly.
So, here are my thoughts… Since most of us are not elite athletes that need to micromanage every aspect of nutrition and exercise, do what feels best for your body. For example, my tummy has never tolerated intense exercise or long cardio sessions with stuff sloshing around well. But I also hate cardio first thing in the morning. This means that while I don’t typically have a meal in the 60-90 minutes prior to exercise, I’m not really completely fasted either.
Here is why this is my recommendation: consistency. Long time readers will have known that was coming. Truthfully, you aren’t going to keep doing something if you feel awful doing it. If it sucks to not eat before a jog, the discomfort shows up during the run, which in turn is going to put you off running. If you, like me, are not a first thing in the morning exerciser, you might find it difficult to manage your meals to get back to a fasted state.
So, experiment around. Try your current go-to cardio workout at different times of the day and under different tummy conditions. See what feels best and try to work that into your routine. Because before the debate over fasted vs fed cardio can continue, you have to be consistent in what you are doing.
How do you feel about fasted cardio, tell us in the comments!
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