Does loss of Lean Body Mass (LBM) ever include reduction in the size of a person's heart muscle?

I am currently taking off pounds, and strongly suspect that I am taking off part fat, part LBM. Over 20 years ago, I was a runner: 20 miles per week at 6-minute pace, a little over 3 miles each run. I understand that runners typically have larger heart muscles than more sedentary folks. I also understand (and have seen confirmed from experience) that muscles previously developed through mass-building exercise undergo "atrophy." They get floppy, if they do not also lose mass.

I don't know enough specifically about the heart muscle to know whether it is more self-adjusting than other muscles. That is, does the heart trim its own mass, sizing itself to fit its owner's activity level?

Or, does previously developed and toned heart muscle mass simply go floppy? Can diet and exercise adjustments slowly re-size it, "cut" it and "bulk" it like other muscles?

Sorry if technicality of the questions is overboard, but wanted to ask here before I see my Dr. -Martin

Lean body mass has nothing to do with the heart muscle. The heart responds to cardiovascular exercise although it gets worked with hard weight training too. But losing or gaining body mass has absolutely no impact on the heart. Eating healthy, cardiovascular exercise, and weight training all owork together to create a healthy heart.

Does loss of Lean Body Mass (LBM) ever include reduction in the size of a person's heart muscle?

I am currently taking off pounds, and strongly suspect that I am taking off part fat, part LBM. Over 20 years ago, I was a runner: 20 miles per week at 6-minute pace, a little over 3 miles each run. I understand that runners typically have larger heart muscles than more sedentary folks. I also understand (and have seen confirmed from experience) that muscles previously developed through mass-building exercise undergo "atrophy." They get floppy, if they do not also lose mass.

I don't know enough specifically about the heart muscle to know whether it is more self-adjusting than other muscles. That is, does the heart trim its own mass, sizing itself to fit its owner's activity level?

Or, does previously developed and toned heart muscle mass simply go floppy? Can diet and exercise adjustments slowly re-size it, "cut" it and "bulk" it like other muscles?

Sorry if technicality of the questions is overboard, but wanted to ask here before I see my Dr. -Martin

Lean body mass has nothing to do with the heart muscle.

Actually the weight of the heart is included in LBM. LBM is everything (muscles, organs etc.) minus the fat.

Martin, I assume the heart would slightly reduce in size if after a period of years you stopped running. You are right that runners (mostly elite runners) have enlarged hearts and if you stopped running the heart would reduce in size (to what degree I'm not sure). However this change would take place very gradually and wouldnt show up in your measurements taken over a short period of time.

If you are losing LBM, you are most likely losing muscle. Are you worried that this (not just stopping running) may lead to some reduction in the size of the heart muscle? From my knowledge, your body would have to have catabolized almost all of your muscle before it started breaking down its internal organs and by this time death is of course imminent.

So, like jsbrook said, as long as you maintain a healthy diet, you wont need to worry. If you are losing LBM I suggest upping your calories.

Of course, I am nowhere near educated enough to answer your question without doubt. Andrew M is a member here and he is also a Doctor (studying to be a heart surgeon). He may be able to answer your question with more confidence and accuracy. Otherwise, just speak to your doctor like you said. :tucool:

My understanding is that heart muscle is unique in our body. The heart is the only "part" of our body made from this incredible muscle. It is really "power hungry" but able to deliver insane output. Someone with more biology/medical knowledge should chime in but just imagine it is a muscle that literally never rests in your entire life. Also a "well trained" heart can increase its output from around 30 bpm to above 200. Even for average people like me it can go from low 50s to high 170s.

Cardiovascular training will strenghten your heart muscle and your heart will grow, much like other muscles. Lack of training will probably make it lose some of its strength/mass but I don't believe that a weight loss will have any effect on your heart muscle.

Elite cyclistst cut down to very low weight, they lose most of their fat and also some (mostly upper body) muscle but they maintain (and increase) their cardiovascular strength, meaning they increase their heart strength.

Yes, it is, in fact, possible to shrink and damage your heart by losing muscle mass too quickly. However, "incidental" muscle loss while pursuing other fitness goals is not going to do this. The only people who really have to worry about this are people who are in a situation for a while where they are literally starving to death slowly, like prisoners of war or heroin addicts, or, more relevantly, to actors who lose lots of muscle mass quickly in order to get jobs playing such suffering people in movies.

The most famous case of this risk is Matt Damon, who cut down from something like a lean 170 lbs to 130 lbs in a few months in order to play a gulf war vet with a heroin addiction in Courage Under Fire. He was lucky to emerge from that one without heart damage.

I suppose if you became obsessed with a no-muscle-mass, plague victim look, it'd be possible to lose enough muscle quickly enough through starving yourself to damage your heart muscle for aesthetic purposes. But you're not going to lose 40 pounds of muscle in three months by accident when you're you're getting cut or cycling competitively - it just plain isn't going to happen.

This is a good argument against people who do get it into their heads that they would look better with less muscle, but injury, especially hip injury, is a better one.

If you do end up a prisoner of war, a heroin addict, in an horrific accident, or with a terrible illness that causes you to lose a lot of muscle, you should probably try to do a little cardiovascular exercise from time to time to try to minimize heart muscle damage. But I suspect you'll have bigger fish to fry at that point in time.

Thanks everyone! You have all encouraged me tremendously. I think I am seeing a common theme in your replies that I can relate to my underlying concern. Namely, that extreme starvation conditions would carry the highest risk of heart damage.

My concern is that I have "yo-yo'd" so many times over the past 30 years - alternating between active, fit periods and sedentary periods - that I might have already done some damage that way. I am dedicated to living the rest of my life in a way that avoids any further damage, and risks of damage, as effectively as possible. Now six weeks into that dedication, I just want to make sure that I'm going along the right track and correct course where necessary.

I'll get my Dr. to confirm my intuition. But I can say without hesitation or hedging that I feel as good now, six weeks along, as I have felt in years. So my intuition is that so far, my weight reduction has been mostly the "good" kind, "probably" a shedding of mostly fat and little if any LBM. I have not had palpitations or chest pains or faintness. I've cut my calorie intake significantly but not "too drastically," I believe. I have not felt weakness in major muscles, like I would expect if I was undernourishing severely. The only major muscle groups I have truly "exercised" in the past six weeks have been the groups used to climb stairs and walk. Those groups are definitely stronger, and I am not huffing when climbing nearly as much as I was.

So thanks again to everyone! -Martin

Yes. I stand corrected. The heart can apparently shrink, but only under extreme and abnormal deprivation conditions. Even sedentary living, which is not good for the heart, isn't bad because it has much impact on its actual size. Healthy eating, fat loss, weight training, and cardio can only help your heart. I'm sure your doctor will tell you the same thing.

Thanks everyone! You have all encouraged me tremendously. I think I am seeing a common theme in your replies that I can relate to my underlying concern. Namely, that extreme starvation conditions would carry the highest risk of heart damage.

My concern is that I have "yo-yo'd" so many times over the past 30 years - alternating between active, fit periods and sedentary periods - that I might have already done some damage that way. I am dedicated to living the rest of my life in a way that avoids any further damage, and risks of damage, as effectively as possible. Now six weeks into that dedication, I just want to make sure that I'm going along the right track and correct course where necessary.

I'll get my Dr. to confirm my intuition. But I can say without hesitation or hedging that I feel as good now, six weeks along, as I have felt in years. So my intuition is that so far, my weight reduction has been mostly the "good" kind, "probably" a shedding of mostly fat and little if any LBM. I have not had palpitations or chest pains or faintness. I've cut my calorie intake significantly but not "too drastically," I believe. I have not felt weakness in major muscles, like I would expect if I was undernourishing severely. The only major muscle groups I have truly "exercised" in the past six weeks have been the groups used to climb stairs and walk. Those groups are definitely stronger, and I am not huffing when climbing nearly as much as I was.

So thanks again to everyone! -Martin

Your heart is unlike any other type of muscle you have, the myocytes being specifically adapted for their specific roles.

Whilst your skeletal muscle (except for your tongue) connects two points, and shortens the distance between them to cause the movement, your cardiac muscle contracts in a coordinated fashion using your blood filling its chambers as its 'anchoring point'. The higher the volume of blood filling the heart (as always, up to a point) the higher the force generated, ensuring that your heart empties itself appropriately each beat, maintaining homeostasis.

The amount of work your heart has to perform is dependent upon a large number of factors; the anatomy (or the problems with anatomy), blood pressure, hormonal drive ('fight or flight' adrenaline and its similar hormones), the return of blood to the heart (breathing can really lower your heart rate), the state of your major blood vessels (they are very elastic when you are young, but become more 'brittle' as you age), and coronary artery disease.

Ignoring as much of my above as possible:-

Does loss of Lean Body Mass (LBM) ever include reduction in the size of a person's heart muscle?

As far as I'm concerned, all non-fat mass is LBM, but there are many different components that go to make it up besides muscle.

I am currently taking off pounds, and strongly suspect that I am taking off part fat, part LBM. Over 20 years ago, I was a runner: 20 miles per week at 6-minute pace, a little over 3 miles each run. I understand that runners typically have larger heart muscles than more sedentary folks. I also understand (and have seen confirmed from experience) that muscles previously developed through mass-building exercise undergo "atrophy." They get floppy, if they do not also lose mass.
Your running in the past will probably have increased your heart size appropriately, as you were loading your heart with exercise. Don't, however equate the gains made through resistance training of your skeletal muscle with cardiac muscle, they are worlds apart. The heart uses virtually all the oxygen supplied to it, disruptions to this supply result in angina through to infarction. This, taken along with the fact that the heart works constantly tells us that cardiac muscle is exclusively aerobic in nature. With exercise, the heart pumps harder and faster, but that effort is still situated along the same line (look up 'Starling's law' if you're interested), and isn't like 'mass-buliding'.

I don't know enough specifically about the heart muscle to know whether it is more self-adjusting than other muscles. That is, does the heart trim its own mass, sizing itself to fit its owner's activity level?
All muscle is self-adjusting. Adaptation is the reason we are top predator, and your muscles are fine examples of this. Resistance training will cause big changes in your skeletal muscles, because of the very wide range of magnitude/frequency of loads applied to them. There's a world of difference between someone sedentary and a powerlifter or bodybuilder in terms of forces applied. There isn't such a wide variation with their hearts however, for 2 reasons. One, even sedentary, your heart is going all the time, and 2, there is a very wide range naturally that the heart can cover without needing to remodel itself.

Or, does previously developed and toned heart muscle mass simply go floppy? Can diet and exercise adjustments slowly re-size it, "cut" it and "bulk" it like other muscles?

Your heart will gain and lose mass depending upon your exercise level, but the changes are much smaller than the changes you can see in skeletal muscles. The notions of 'cutting' and 'bulking' simply don't apply. The heart remodels itself to the appropriate size. Diet has little effect upon the cardiac muscle cells themselves directly. A fatty diet, and obesity will increase the amount of fat surrounding a person's heart, and will contribute to the risk-factors for coronary disease however.

Sorry if technicality of the questions is overboard, but wanted to ask here before I see my Dr.
You've barely even scratched the surface when it comes to cardiac pathophysiology, Martin. There are virtually no situations where getting to a healthy weight through sensible diet and exercise will be detrimental.

Andrew.

Bottom line:



There are virtually no situations where getting to a healthy weight through sensible diet and exercise will be detrimental.

Andrew.

EXCELLENT!! Thanks Dr. Andrew for filling in so much on the technical side. I can go with that bottom line, too. :) Marcus says you're on path to be a heart surgeon. I'm sure you'll have many happy clients! :tucool:

Congrats too Andrew on impending daddyhood! Speaking from experience, March is a good month for that first time! ;)

-Martin