Calorie burning and fitness

Had a discussion about this last night and couldn’t agree, so hope the board can provide the answer.

Say we have two men of equal height and weight. One is very fit, one is badly out of shape. We put them both on a threadmill for an hour, at the same speed. At the end, out of shape guy is absolutely covered in sweat, exhausted and his heart-rate is through the roof. Fit guy barely broke a sweat and his heart-rate is only slightly raised.

Question: Did out of shape guy burn more calories or is the calorie burn exactly the same for both guys?

If the fit guy has more muscle mass than the out of shape guy then he burnt more calories because only muscle burns calories.

(Fat burns calories too, just not as many/unit weight as muscle does.)

The fit guy burned fewer calories because his muscles have, through training, learned to perform that activity with efficiency.

That’s really incorrect. Fat burns calories too, just not as much.

I’m not sure of the answer to the OP’s questions, but I would also suggest that since the unfit guy doesn’t normally exercise, he’s probably much less efficient then the fit guy, which would cause him to use more energy (calories) to do the same amount of work as the fit guy.


This is absoutely correct and seems to fly in the face of logic, but if you think about it doesn’t.

I was involved in a study at the U of Chicago, where we did sports medicine anyway one thing that came out and was totally bizzare to me was the MORE fit you are the harder you have to try to improve said fitness

For instance, with my heart I had to run 60 minutes to 90 minutes 5 days a week at 85% of my theoretical max heart rate, to show any measureable improvement in my heart’s fitness.

Now get this -> We also had Olympic atheletes participate and they had to to work out at 95% of the theoretical max heart rate to show improvement.

If you think about it, it does make sense. Because the results compare improvement over the person themselves and NOT between different people.

An Olympic calibur athlete is already more fit than me, so he of course WILL have to train harder to improve his own fitness. Why? Because he’s that much better to begin with.

The out of shape guy is gonna lose more weight (though the differences may not be huge, they will be measurable), because his body hasn’t adapted to being fit yet. As he becomes more fit, he will have to work harder to shed calories and improve fitness of his heart and such things.

Why? Again, because your comparing fitness rates among one person’s past, present and future, not between different people. And that’s why it seems “off”

Your question is interesting, yet does not lead to something that can be useful. The rate of calorie burn is very complicated. Exercise can increase the calorie burn for a period of time after. A better question might be how many extra calories are burned by either fat or fit over an extended period of time? The calorie burn is also affected by the intake of the person involved whether fat or fit. A fat person can go on a severe diet and cut their metabolism way down. While they may burn more calories working out over the same period, they then burn far less during the rest of the day because the body is in starvation mode. A fit person might take in thousands of calories and burn them off due to high metabolism and not just exercise. There seems to be a terminal amount of calories that the body can absorb. It may be higher with fat people. We all know people who can eat enormous amounts of anything and still don’t gain weight even without exercise. The metabolism is also affected by the level of thyroid output. Weight gain or loss is strongly influenced by this gland. Weight loss products often contain kelp or iodine as this can trigger greater thyroid output and higher metabolism. (Too much can also cause thyroid problems. Therefore, the amount of iodine in supplements is limited.)

Sorry for rambling on here. I just felt that your real question might go beyond what you asked.

Thanks all.

This question came about because my friend was on a threadmill in the gym watching a girl struggling and, to be a bit evil, set the machine at the same pace and target distance and completed the workout without too much effort. I contended that she probably got the “better” workout even if they did the same distance at the same pace. My friend argued that it was purely a mathemical matter moving weight over a certain distance and that how hard you have to work to achieve this distance has no or a very neglible effect on calorie burn. Which seemed wrong to me. I mean, exercise programs often speak of an optimum heart-rate for calorie burning. I think the fit person would need to step it up a bit to reach the same goal. Am I wrong?

Al Bundy, I also take your point. I am really oversimplifying for the sake of the argument. For me personally, apart from the metabolism thing you highlight I think it is also the case that exercising gives people energy, making them less likely to sit on the sofa and more likely to be doing something physical, i.e. exercise breeds more exercise, so there’s a knock on effect in calorie burn too. So I cerntainly do not mean to say it is best to be unfit because that makes it easier to burn calories!:eek:

Heart rate is directly related to effort(how good a workout you get).

For general fitness 65-80% is the range to aim for. The difference is the fitness level that each person is at.

Take two people, one can run at 6:00min./mile, the other 8:00min./mile. For both they might be working at 75% but if the faster person ran at the slower person’s pace he/she might find themselves at only 55% and not getting a good workout at all.

So he would say that bicycling 10 miles is as good of a work out as running 10 miles?

Oh no, cycling is muuuuuch more efficient! Apples and Oranges!

What he’s saying is this. Let’s say we have a one mile distance. First guy walks it in 15 minutes. Second guy runs it in 8 minutes. Third guy crawls it in 2 hours. They each did the same amount of work (assume all 3 guys weighed the same). They each moved their body of x weight over y distance. Therefore, they all burned the same amount of calories, same work done. Now of course, it’s not that simple due to heart rate, efficiency, etc. But that’s the principal.

I’ve used a couple of different online exercise calorie tools to verify this. When people want to talk to me about their walking workout, I simply ask how far they have gone to get an idea of how much work they did.

Ah. He does understand that efficiency matters, that it isn’t just a “mathemical matter moving weight over a certain distance and that how hard you have to work to achieve this distance has no or a very neglible effect on calorie burn.”

Indeed the difference in efficiency between cycling a distance vs running it is much greater than the difference between a trained fit individual running a distance and an untrained unfit individual running the same distance, but the difference is just as real.

To use your specific illustration, it is just false to believe that each of those guys did the same work because they each moved the same mass over the dame distance; just as false as to claim that is the same work to move that mass that distance by bicycle or by swimming.

That’s the most basic answer. We can go deeper if you’d like and analyze according to the sort of fit individual and how they complete the distance to show how far off this can get. Let us imagine that our fit subject does endurance training. He has developed his highly efficient slow twitch fibers and is completing this distance using those primarily. As a result he has burned close to nothing. Our out of shape subject, huffing and puffing as he is, is not only using the less efficient fast twitch fibers, he is pushing them into the even more inefficient anaerobic zone for parts of the distance. Lots of calories burned if he can make it the distance doing that. But what if our out of shape subject walks? Well walking is a very efficient way to move. He may burn less the fit subject doing that.

If you put some hair, plain, on a threadmill will it make cloth?

Yes, that’s exactly what he’s saying.

The problem is that calories (as used in the exercise world) refers to different things.

There is calories in a purely physics sense - mass moved over a distance. By this measure, any two people of the same weight covering the same distance over the same course will have use the same number of calories (no matter how fast or efficiently they have done it).

Then there are calories in food - this is a chemical measure of energy in food, and is also constant. 200 calories of porridge is 200 calories, no matter who eats it.

Then, in the middle, is the human.

People have different digestive efficiencies (within a range), so those food calories end up being digested and processed differently in different people. Some people (particularly the formerly obese) are more efficient and extract and utilize more energy from food (again, body store calories) than others.
People also have differences in biomechanics, the conversion of stored food energy in the body (still calories) to actual movement. Some people are more just efficient (naturally, or by training), turning calories into movement with little waste. Some are not, generating wasteful excess movement and heat.

Exercise machines can easily measure calories (in the physics sense, mass moved by distance). However, people like to think of exercise in terms of body store calorie expenditure, and relate it to food calories. So the calorie calculation displayed uses some additional information (weight, age, height, heart rate) to make an estimate (based on research, but averaged) of body store calorie use. But it cannot really estimate biomechanical efficiency, or digestive efficiency, so it is always off for an individual. The trick is to use it as a guide, not gospel truth, and realise that a 200 calorie workout may not equate to a 200 calorie donut. The only way to really measure that is on a monitored workout with Oxygen/CO[sub]2[/sub]/temp/heartrate sensors and biomechanical analysis. And very few places can do that. However, some companies (notably Polaris) claim that their heart rate monitoring system gives a very good model of calorie use. I am yet to be convinced.


The efficiency does matter - it’s mass x distance, all other things being equal. Mass x distance swimming, for example, needs more energy because a lot of efficiency is lost due to water resistance. Running is slightly less efficient because there is additional upward effort made with each step. Sliding on your ass down a long icy slope takes almost no energy at all (well, it does, but the energy is not provided by the person, it’s provided by potential kinetic energy released by gravity. And so on.