Does working out on an empty stomach burn more body fat?
Does working out on an empty stomach burn more body fat?
Nutrition Diva is hosted by Monica Reinagel. A transcript is available at Simplecast.
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When is the Best Time to Exercise?
Scott writes:
I've heard that the best time to exercise is in the morning before you eat breakfast because your body is still fasting from not eating overnight which causes you to burn more calories. Is this true?
Well, Scott, how many calories you burn during exercise depends on how hard and long you exercise, and not how long it’s been since you’ve eaten. But there is some research showing that if you exercise after a fast (such as first thing in the morning) you will burn more body fat than if you did the same exercise later in the day.
Why? Your body stores energy (or calories) in a variety of formats and places in your body. You store a little bit in your blood, a little bit in your muscles, some in your liver, and the rest you store as body fat.
It’s a little like storing your money in a number of places. You probably have some in your wallet, possibly some more in your dresser drawer, some in a checking account, and maybe the rest is in a money market account. Which account you withdraw funds from will probably depend on how much you need and how fast you need it.
Similarly, what type of fuel you burn during exercise depends in part on the balances available in your various fuel storage accounts. In the morning, your blood, muscle, and liver “accounts” are going to be at their lowest, because your body will have been drawing on them to pay for metabolic activities during the ten or twelve hours since you had your last paycheck, I mean, meal.
So, if you exercise first thing in the morning, before you’ve refilled those energy accounts by eating some breakfast, you’re going to have to tap into those fat stores that much sooner. The question is, does this really change how much body fat you will lose in the long run?
Just like with your money, regardless of which account you withdraw from, you’re still spending the same amount. If you spend more than you deposit, your net worth goes down. And when you burn more calories than you take in, you’re going to lose body fat.
Exercising on an empty stomach may increase the amount of body fat you burn during exercise. But your body alternately makes and burns body fat all day long, transferring fuel in and out of its various accounts. So, you might burn a bit more fat while you’re exercising on an empty stomach but then burn a bit less fat later in the day. Over the long term, the amount of fat you have in your body depends mostly on how many calories you take in versus how many calories you burn.
Now, I’ll admit there are some other factors that come into play. What and when you eat and exercise affects and is affected by hormone levels; and that does affect your metabolism to some extent. But these effects have been blown way out of proportion in the popular media and urban legend mill.
In fact, I think there are other factors that will make a much bigger difference in how much body fat you can burn with your exercise program. If working out first thing in the morning fits your schedule better, then an early morning work-out is probably going to be more effective for you.
On the other hand, if you find that you get a better workout at the end of the day when you’ve some steam to blow off, then that’s probably the best time of day for you to exercise. Or, maybe you have a workout partner who is only available after work. Having a date to meet someone at the gym or track might make you much more likely to follow through with your exercise plans.
Good nutrition before and after exercise is important too. But the exact timing of your meals and exercise is largely a matter of individual preference. Personally, I feel awful if I exercise too soon after eating so I prefer to exercise before breakfast. On the other hand, if exercising on an empty stomach makes you tire more quickly and quit earlier, that’s probably not going to be as effective for you as exercising later in the day.
Similarly, some people find that early morning exercise gets their whole day off to a better start; it improves their mood, makes them feel energized, and motivates them to eat better all day long. But others find that exercising in the morning increases their appetite and makes them more likely to overeat later in the day. I also know people who swear that exercising in the evening helps them cut down on after-dinner snacking.
Obviously, these things have a lot more to do with logistics, personality, and psychology than they do with metabolism--but they probably have a bigger impact on the results of your exercise routine than the time of day you exercise. Here’s the bottom line: the exercise routine that will burn the most fat is the one you can do regularly and vigorously. My advice, therefore, is to exercise when and how it’s most convenient and enjoyable for you.
For another point of view on this, you can get a personal trainer's advice right here on Quick and Dirty Tips by checking out Get-Fit Guy's episode on "What to Eat Before and After Exercising."
For those who want to dig into this topic deeper, I’m going to put a link in the show notes to a very good article by Tom Venuto, originally written for Iron Man Magazine.
Although he effectively diffuses most of the quasi-scientific claims about enhanced fat-burning, Tom ultimately comes down the side of exercising before breakfast—but mostly for the kind of reasons I’ve listed above. The article is a lot more balanced and rational than most of what you’ll find on this subject and it includes a lot of good references. So, if you’re interested in reading further, I think it’s a good place to start.
This is Monica Reinagel, the Nutrition Diva, with your quick and dirty tips for eating well and feeling fabulous.
These tips are provided for your information and entertainment and are not intended as medical advice. Because everyone is different, please work with your health professional to determine what’s right for you.
You can contact me at nutrition@quickanddirtytips.com or leave me a voice mail at 206-203-1438. Better yet, post your comments and questions on my Nutrition Diva Facebook Page or via Twitter.
Have a great day and eat something good for me!