Which burns more calories (running related)

So, I decide to run 10 miles today. Am I ultimately burning more calories (all things considered) if I:

a) Run them all at once
b) Run five miles in the morning and five in the evening
c) Some other combination (3 in the morning, 7 in the evening. 3 in the morning, 3 in the afternoon, 4 in the evening).

Just a bit curious.

I had always heard that it takes 20 minutes of exercise before your body will start using its own stored fat as a source for calories. So if you’re interested in burning those calories (and if you believe the 20 minute overhead rule), you should run all ten miles at once after a sedate twenty-minute warmup. My cross-country coach would typically have us go out and run a half-mile before the main workout of the day, stretch, do some calisthenics, and run another half-mile at a jog, and then we’d walk quickly over to wherever the workout was starting. I have no good way to empirically measure whether that actually burned more calories, because we always did it that same way.

Another option is to run twenty minutes in the morning to “kick-start” your metabolism for the day, and then come home and run the remaining distance. You can run your morning workout for speed training (run 2:30 out and then turn around and run back much faster; rest until 5:00; run out to 7:30, back fast and rest until 10:00…) and your evening workout for pacing and calorie burn.

In my experience, a morning workout feels good, and my food cravings are generally for healthier foods when I’ve worked out in the morning – it may not precisely burn more calories, but it definitely contributes to reducing my total calorie load.

I’m a pretty avid runner, and have always done my running early in the morning. But, time constraints lately have forced me to split my runs. It just doesn’t feel like I’m doing as much when I split my workouts in two. It doesn’t feel as effective. Though, that might be completely in my head.

The way I understand it is that the amount of calories burned during the
workout(s) would be the same no matter how you broke up the 10 miles worth of running. The effects on your metabolism after would be different, but probably trivial.

When you exercise, obviously, your metabolism increases and you burn more calories. This just doesn’t grind to a stop the minute you finish your 10(or 5) mile run(s). It slowly trickles down back to the basal rate depending on length and intensity. If you worked out multiple times during the day to where it never trickled down all the way back to normal before you started your next workout your metabolism would be permanently raised(kind of like the effects eating small frequent meals throughout the day).

How much, in terms of calories a day, this would have an effect I don’t know and I’m not sure anyone does. My best SWAG is that it is completely trivial and nobody should ever worry about it. If you are in shape enough to run 10( or even 2) miles a day then do it. I would recommend running at least a mile or so of it in the morning, though. It feels great and, just like eating breakfast, helps bring you out of the fasting state you’ve been in for the last 6 or so hours. Also don’t foget at least some(at least) light muscle building exercises so you can gain more lean muscle mass.

The exact time it takes depends on how much oxygen you’re consuming. Oxygen is the limiting factor in the reactions that free stored fat, so the more you can get in, the faster that process goes. Note, however, that the process of freeing stored fat starts as soon as you do any exercise-type activity–so if you lift for 30 minutes and hop on the treadmill immediately afterwards, there’s no waiting for fat oxidation to kick in.

In light of this, the longer you run at once, the higher a proportion of the caloric needs will come from fat stores. So the total amount of calories should stay the same, but you’ll burn more fat if you run all 10 miles at once. I don’t know whether it can be significant enough to worry about, though.

I’ve heard that if you run too fast, you stop burning fat and you start burning sugar (glucose).

When I told someone I run seven-minute miles on my treadmill (8.6 miles an hour), they said I was running too fast to burn fat and that I should slow down if I wanted to burn fat.

Any truth here?

You would burn through your free glucose before you started burning fat.

See, I thought of this. But, in the end, would this matter. Even if you got off the treadmill before burning any significant fat, you have burned through your muscle and liver stores of glycogen. That would have to be replaced, and it would be replaced by the fat stores. Correct? So even if you aren’t directly burning fat, eventually the fat is going to come into play.

Yes, except that if you really had used up your glycogen stores, you’d be getting off the treadmill face-first.

I didn’t mean use them up totally. And that wouldn’t be the first time that I’ve woken up writhing next to a treadmill wondering what happened for the past few minutes.

Whisky and treadmills don’t mix, kids.

I agree with I_Know_Nothing that the effect on calorie burning is most probably trivial.
It is true that there will be an advantage because of metabolism staying higher with several runs. On the other hand, if you run only one run, you will need more of an energy source rearrangement, which is very slightly costly.

As for the side question about which burns most fat: If you burn the same number of calories in a period of time, it will result in the same loss of fat, if your eating is the same. I guess that you will be hungry if your glycogen stores are low, which they will be after each of the several runs. And maybe you will not be proportionally more hungry after 1 long run. However this is pure speculation about something I know nothing about.


In physical activity we always start by using glycogen and then mix it with an increasing amount of converted fats. No matter your running speed.

Absolutely not. I hear this myth frequently and I think it is perpetuated by personal trainers at local gyms who, as studies show, frequently know nothing about nutrition, or even kinesiology beyond the very basics. (Although I have known some who are knowledgeable)

It is a fact that, the closer you are to VO2 Max(basically the hardest you can possibly exert yourself) the higher percentage of fat calories you burn as a percent of total calories burned. But you are definitely burning more total fat calories. (a rare exception is when you are just under 100 percent VO2 Max, which makes you use glucose almost exclusively, but this is obviously not a sustainable pace).

Take 40 percent of 100 and 30 percent of 200. Which one’s larger. (I just made up those numbers but it illustrates my point)

The time you are burning the highest percentage of fat calories is when you are sleeping. By the same myth logic you say the best way to lose weight is to sleep all day.

There are reasons for staying in the “fat burning zone” as it says on many cross training machines, but burning extra fat is not one of them. Making sure you are not too sore to exercise the next day, avoiding injury, and knowing that you can get quality exercise without overexerting yourself are a few reasons I can think of off the top of my head. Most of these reasons do not apply so much to seasoned athletes.

If you are in shape enough to run seven minute miles day after day then more power to you. You will not burn more fat calories by running slower. I would just make sure you mix in at least some strength training. I see to many jogaholics who never do anything to build or sustain lean muscle mass. Its a good way to help keep off the extra pounds.

Actually, one can expend energy at a faster rate by relying on anaerobic metabolism, but this is not a sustainable level of exertion. I remember doing VO2 max tests, and the oxygen uptake increased pretty linearly with workload until hitting a plateau at which point the workload increased but oxygen uptake stayed constant – needless to say, this anaerobic stage lasted only a couple of (painful) minutes, but it was the way for the tester to ensure that VO2 max had indeed been reached, and you weren’t just stopping because you were a wuss. :slight_smile:

In fact the amount of time that can be spent anaerobically varies among individuals, and is trainable. I’m going to quit here, as I am definitely not an exercise physiologist.

Yup, I was told this by a Spin instructor at the gym. She had the most convoluted way of explaining it that I knew I should just stop listening and do my own research.

I know nothing about the science behind it, so I just go with: whatever way allows me to actually get the amount of exercise in is the best way for me. I know I need to do all my running at once, preferably in the morning. Too many things come up during the course of a day to guarantee that I’ll get back out there to finish logging in the miles at the end of the day.

I just realized a long time dream of finally having a home big enough to put in a commercial grade treadmill. The electrician comes next week to put in the 220 V outlets it requires. So, I’ll be free to log in the miles whenever I have the time.

I have a long established morning exercise routine (about ten years now, of only rarely missing a workout). But, I would always like to do about 20 minutes more. I just don’t have the time before work. I’m already getting up before 5! If I can put in 20 minutes after work, that would be great.

If you think putting in 20 minutes after work would be great, then just do it! The mirror and how you feel will tell you the effect it has. Anything else is speculation.

In case you want to know just how complicated it can be…

A New View of Energy Balance

If you’re interested in the subject, Dr. John Berardi has recently published a new model for the calories in vs. calories out idea. You can find it here:

A New View Of Energy Balance

I’m envious! On the days that I run, I’m up at 4:45 and out the door just after 5. Like you, I am going to want to go longer at some point, and I’m just not sure where the time will come in. I have work and 2 toddlers, which is why after work isn’t always a reliable option. I hope that, in 10 years, I can also say that I’ve rarely missed a workout!