Cardio
February 14, 2011
Do you drag yourself out of bed first thing every morning to perform cardio before breakfast in hopes of jacking up your fat burning capacity? If so, go back to sleep!
The fact is, performing cardio on an empty stomach does little to increase fat burning over exercising in the fed state. I recently wrote an article for the NSCA Strength and Conditioning Journal titled, Does Cardio After an Overnight Fast Maximize Fat Loss? that examined the research on the topic. Here is a synopsis:
1) When exercising at moderate to high intensity, the body breaks down substantially more fat than it can burn for fuel. This effect is magnified in experienced exercisers. Ultimately, the fatty acids get “trapped” due to exercise-induced ischemia and are unable to reach the muscle for oxidation. Thus, while there is an increased breakdown of fat when you don’t eat prior to performing cardio, the additional fatty acids don’t get burned and simply end up getting stored again in fat tissue.
2) Studies show a significantly greater amount of calories burned post-workout when you eat prior to training compared to if you don’t (i.e. the “thermic effect of exercise). The upshot is that performing cardio while fasting blunts fat burning following the exercise bout, which potentially can add up to a substantial amount depending on exercise intensity.
3) As much as 50% of the fat burned during exercise comes from intramuscular triglycerides (fat stored within muscle). This fat serves as a reserve energy source and has nothing to do with physical appearance. Thus, even if any additional fat was burned during the bout by not eating, the effects on body composition would be far less than simply looking at the total amount of fat burned.
4) Last, and perhaps most importantly, fat burning must be considered over the course of days—not on an hour-to-hour basis—to get a meaningful perspective on its impact on body composition. The human body is constantly adjusting its use of carbs versus fat. As a general rule, if you burn more carbs during a workout, you inevitably burn more fat in the postexercise period and vice versa. It all evens out in the end.
Bottom line: When you do your cardio is really not important. Like the Nike commercial says: Just do it!
Stay Fit!
Brad
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Thanks for the article. I always eat before my workouts because I look and feel like the woman in the picture if I don’t!
What follows is more of a question for Brad than a comment. (Can I submit questions here or not?)
How many grams of carbohydrate, protein and fat should be consummed before a morning workout for optimal fat burn and to fuel the workout?
For instance, I eat about 25 grams of protein (whey powder), 20 grams carbohydrate (oat bran or shredded wheat cereal). I eat at 6:15 and exercise at 7:30 because that is the only time frame I have for my eating before my morning workout. I do a 30-45 minute high interval session of cardio 5 days/week and weight train later in the day for 3 days/week.
Am I eating enough before my workout?
Comment by Kathy — February 15, 2011 @ 10:28 am
Hey Kathy:
Based on your timing, it might be better to have liquid carbs (i.e. juice) instead of the bran cereal. Liquids require much less digestion, and given that you only have a little more than an hour from eating to training, it’s better to avoid having undigested food in your stomach.
Brad
Comment by Brad Schoenfeld — February 18, 2011 @ 1:49 pm
Hi Brad,
I am at about 11% body fat and starting to cut up for summer, when reaching single digit fat levels, i am always left with some hard to lose fat around my abs, chest and lower back (obliques).
Does your research apply to all areas of fat loss, for instance, I’ve followed the stubborn fat solution protocol (which is in ‘the stubborn fat solution’) written by internet guru and trainer Lyle Mcdonald.
The book recommends fasted cardio (while on a ketogenic diet) : high intensity to start (a few quick sprints/then rest) – to release fat stores – and then low intensity to oxidize them in combination with a substance called yohimbine HCL which is an alpha-2-receptor antagonist (fat cells having more alpha2 receptors than beta- apparently my problem) which only works in the absence of insulin -hence why you have to be fasted.
OK, with that explained, I’d like to know if you have ever studied this issue and or, have any thoughts on it.
and more importantly in regards to your research article ((which I (or my school {:(} don’t have access too)) – I’d like to know at which intensity it is your body is found to “double it’s nitrogen losses” and if this could be attenuated simply lowering this intensity (or following your aerobic activity with a protein supplement) – and the same goes for the use of Intramuscular triglycerides – at which intensity are these used and could this also be attenuated by exercising at a lower intensity?
Comment by Steve — March 16, 2011 @ 12:57 pm
I know Lyle. He is a sharp guy and I’m sure his opinion on the topic is well researched. That said, I’m not familiar with the specific program you’re referring to and I’m unaware of any specific research on fasted cardio while using yohimbine. While theoretically there might be a rationale, I couldn’t comment on its efficacy.
From what I recall on Lemon’s study about protein catabolism during a glycogen depleted state, I believe the subjects exercised at moderate intensity (around 60% VO2 max which equates to about 75% MHR). I should note that other researchers have shown similar results (1). Could this be attenuated by lowering intensity? I would think so (I haven’t seen specific studies looking at protein losses associated with very low intensity cardio), but I would still think you would have an increased protein turnover compared to a fed state. As far as IMTG, optimal usage is around 65% VO2max, so you would reduce their contribution at lower intensities.
All this said, I think you’re missing the key points here. First, it’s calorie burning that is the most important aspect of cardio–burn more calories and you’ll burn more fat. Reducing intensity to very low levels will necessarily burn fewer calories and thus burn less fat (besides the fact that you’ll spend a ridiculous amount of time on the bike or treadmill). And perhaps more importantly, the body is going to adjust its substrate utilization later on so that ultimately the ratio of fat burned is not going to change. Ultimately you’re going to excessive lengths to end up in the same place.
Brad
1) Blomstrand E, Saltin B. Effect of muscle glycogen on glucose, lactate and amino acid metabolism during exercise and recovery in human subjects. Journal of Physiology. 1999;514:293–302.
Comment by Brad — March 16, 2011 @ 2:24 pm
Thanks for the quick reply Brad, I appreciate the feedback.
The reason I’d be willing to burn -less- total fat (with low intensity/fasted state) is the idea that whatever I am burning; is ‘stubborn’ fat (as Lyle makes mention in his book).
“the body is going to adjust its substrate utilization later on so that ultimately the ratio of fat burned is not going to change. ”
This is another area of concern of course, but i wonder what effects this has in the context of a ketogenic diet, where there is no other substrate other than fat.
Does that sound comprehensible?
Thanks again for sharing your knowledge on the issue.
Comment by Steve — March 16, 2011 @ 3:15 pm
Hey Brad- I know this article is old news, but I have been up and down PubMed, Alan Aragon’s RR, and pretty much anything I could find on forums or articles through Google trying to find specific guidance on pre-cardio macro/food recommendations.
I know that you mention above (as well have mentioned before) that taking in specifically 1/8 gram of protein per lb/bw and 1/4 gram of carbs per lb/bw prior to morning cardio (HIIT) is preferred, but is there any benefit to taking in just protein, just carbs, a BCAA-combination of one or the other, or even an MCT prior to cardio to maximize EPOC and therefore lipolysis?
Comment by Loren — July 25, 2014 @ 1:06 am
I don’t think that any of these factors will significantly impact long term fat loss. I have a study underway that should hopefully provide some more answers on the topic.
Comment by Brad — July 26, 2014 @ 1:45 pm