You will lose your lean mass if you just do cardio

howeclectic

Its hard to know anything for sure... but one thing I notice... Every study seems to me to be fundamentally flawed. Especially for HIGHLY motivated individuals. Yes losing weight likely will lead to lean body mass loss. However, I don't see too many reliable studies around individuals who do INTENSE cardio (Interval training, sprinting, Hockey, Etc). A lot of the studies i see cited refer to low effort, low intensity cardio.

I recall a lot of studies that centered around swimming not being an effective means of weight loss. They would do these studies taking untrained swimmers and throw them in a pool and have them swim laps. (these people likely thought they were burning crazy calories). None of them would lose weight. However, where were the studies on trained swimmers. I was a competitive for 13 years (starting at age 5). I can tell you... swimming at an Athletes level... Varsity highschool... 3 hours a day.... you lost weight and added muscle.... The studies just proved that meandering exercises dont do much....

crisanderson27

Here's my N=1 example.

Went from 210lbs to 154lbs in 9 months. Calorie controlled diet with approximately 150g protein averaged for day. Exercise choices was jogging, boxing & some bodyweight resistance exercise.

I went from fat to skinny fat. I know I lost a LOT of LBM. (no dexa scans or anything but by the end I could only bench 110lbs 1rm, which I previously did sets of 10 of) If I had my choice again, I would have done it slower and included resistance training from the start.

So for me, cardio only (even though I did do some other resistance training) definitely resulted in a large loss of LBM. I really wish I had a pic of me when I was twig skinny fat but unsurprisingly, not many photos taken in that time period

Boxing is resistance training which is great for muscle retention, so it sounds like it may not have been the absence of weight training that caused you to lose LBM, but more likely, overworking yourself in your cardio sessions combined with a calorie deficit.

I use boxing (100lb heavy bag) as my ONLY form of cardio (except the 4 minute tabata rowing session for warmup before lifting) lol.

Glucocorticoid

The reason you see that so many posts on MFP telling us that we will lose muscle if we do cardio only is because there is a large MFP population that comes to these forums from bodybuilding.com and/or other body building sites. You can even see the same catch phrases in many of their posts.

Of course you can keep muscle with cardio only. Muscles that are being worked regularly do not whither away, no matter how you work them.

Do you honestly think it's this simplistic? So people just lift weights for fun while in a deficit?

An hour of low intensity cardio won't usually cause problems, but let's take it to another extreme - three hours of high intensity cardio, done multiple times a week. As you go to a higher and higher states of intensities, you tend to recruit more type 2 muscle fibers while sending an "endurance signal" - this means the fibers need to adapt to the signal, which means becoming smaller. Combine that with a caloric deficit, and low protein intake, and this is bad news. Vaguely speaking, in that situation there is a higher likelihood of muscle loss, but even that will depend on various factors - to name some:
1. How overfat the individual is
2. Around workout nutrition and total daily caloric/macro intake
3. The rest of the training program (looking at frequency, volume, and intensity).
4. Genetics/gender
5. Other factors I'm overlooking at the moment

Of course, things get further complicated with the newbie effect. And when people are actually losing weight, even in the cases of muscle loss, the muscles hiding behind the fat become more apparent due to the accompanied fat loss, giving a more "toned" look, which adds on to the confusion. But none of this changes what I described above.

secretlobster

How is boxing resistance training?

Okay, my phrasing is wrong. Boxing is not resistance training in the way that weight training is, but it would be false to count it as a pure cardio workout that does nothing for your muscle conditioning. I built muscle JUST through boxing.

The problem with a lot of arguments here is that people who are claiming to have lost muscle mass doing cardio have lost SIGNIFICANT amounts of weight on a calorie deficit. You're not going to be able to maintain your current musculature if you're consuming fuel for a smaller person, no matter how much fat you lose in the process.

belgerian

Agreed to many variables to make a generalized statement. If you have low body fat to begin with like less than 6 percent than yes if you have a deficit you wil. Now if you were like me about 100 lbs overweight or morbidly obese or close to it than no I did just primarly cardio running consumed between 1600 and 2000 cal and the weight just melted off my runs were 1 hour to 1.5 hours today I still run 8 miles 5-6X a week. I am now gearing towards some form of resistance training. My legs are very toned now my upper boddy well still some work to do. Oh yea and I just ate whole foods mainly oatmeal for breakfeast, fruits and veggies and yogurt for lunch and something light for dinner. Few light snacks here and there apple,yougurt, almonds, veggies cheese sticks. And now I run outside fairly hilly area I might add so the 8 mile run if you were to level it out might be closer to a 10 mile on a level elevation. I also keep my arms up and my abs tightned while running. Dont get me wrong I think strenght training is important and it is something I need to add to my overall fitness plans I just have not yet.

Abells

I would like to see some scientific proof that you'll lose lean mass or become "skinny fat" by just doing cardio. Honestly, I haven't lifted weights since my early 20's. I've run, done yoga, done martial arts for years... I had a DEXA scan done in 2004 at 29 years of age that showed I have 120 lbs of lean mass and I had one done a few weeks ago that showed the same 120 lbs of lean mass. I haven't lifted a single weight in that time and my diet has been all over the board, two pregnancies... not to mention 8 years have passed.

So... why is it that people are told not to do cardio only? If you already have a decent muscle base, why not just burn off the fat? I don't understand. It seems pretty hard to lose muscle... there was a time I wanted to.

You've just stated that you do yoga (static strength resistance training), martial arts (involves explosive strikes and kicks which is anaerobic and considered resistance training). So you JUST haven't been doing cardio only.
And lean mass doesn't ALWAYS mean muscle. You can get higher density in your bones, organs can gain mass etc.

But there have been studies done that show if protein balance is insufficient, muscle breakdown occurs.

Not much of a problem for the average runner of course - a jog around the block or even a 5k is not the same as a distance runner in training who does a half-marathon every day, and sprinters probably come under the strength training header since they're doing brief spurts of anaerobic activity.

Cyclists however can easily wind up with elevated protein breakdown - good thing you guys tend to drink lots of sugar water (sports drink). Insulin inhibits the breakdown of muscle protein...

And you do want to replace the glycogen stores pretty much immediately for optimal sports performance(Sports Med; 21(1), 7-17, 1996.) - it does make a difference for both us lifters and you endurance guys.

Plus, if glycogen stores remain remain low, muscle protein breakdown can result and lead to loss of muscle mass (Journal of Applied Physiology; 48, 624-629, 1980) - again not neccesarily a concern for the once-around-the-block amateur, but for the long distance/long duration crowd who spend hours on the elliptical, definitely.


A.C.E. Certified Personal Trainer/Group Fitness Instructor
IDEA Fitness member
Kickboxing Certified Instructor
Been in fitness for 28+ years and have studied kinesiology and nutrition

^ this guy

Klem4

Interesting, will read more later!

pennybelle

bump

magerum

I dont have time to provide links and such but I can tell you this. I lost 160 lbs over the last year with just diet and cardio. My bench max went from 315lbs to 170lbs. Tell me that's not loosing lean body mass.

What were you eating? How much protein? Taking a year long break from lifting(regardless of diet) will cause strength loss.......

I was in heavy deficit for the year. For the first 7 months it was a regular 3000 calorie a day deficit. I was only eating about 70 - 80 g of protein daily. It was all in the name of rapid weight loss, which worked. I'm currently bulking to try and regain some strength. My only regret is not hitting the bench at all over the last year. I've seen some nice newbie gains the last 3 weeks though, kinda' starting all over. Just this time my body fat % is optimal! It's a marathon, not a sprint right?

I do miss the strength though

-M

bcattoes

The reason you see that so many posts on MFP telling us that we will lose muscle if we do cardio only is because there is a large MFP population that comes to these forums from bodybuilding.com and/or other body building sites. You can even see the same catch phrases in many of their posts.

Of course you can keep muscle with cardio only. Muscles that are being worked regularly do not whither away, no matter how you work them.

Do you honestly think it's this simplistic? So people just lift weights for fun while in a deficit?

An hour of low intensity cardio won't usually cause problems, but let's take it to another extreme - three hours of high intensity cardio, done multiple times a week. As you go to a higher and higher states of intensities, you tend to recruit more type 2 muscle fibers while sending an "endurance signal" - this means the fibers need to adapt to the signal, which means becoming smaller. Combine that with a caloric deficit, and low protein intake, and this is bad news. Vaguely speaking, in that situation there is a higher likelihood of muscle loss, but even that will depend on various factors - to name some:
1. How overfat the individual is
2. Around workout nutrition and total daily caloric/macro intake
3. The rest of the training program (looking at frequency, volume, and intensity).
4. Genetics/gender
5. Other factors I'm overlooking at the moment

Of course, things get further complicated with the newbie effect. And when people are actually losing weight, even in the cases of muscle loss, the muscles hiding behind the fat become more apparent due to the accompanied fat loss, giving a more "toned" look, which adds on to the confusion. But none of this changes what I described above.

Yes, you can overdo cardio and eat a bad diet. You can also keep LBM with cardio only IF done properly and while eating a proper diet? Does that make it all better?

eganita

Thanks for posting.. interesting topic and great info. I want to save this for later to read in more detail

michellekicks

I would like to see some scientific proof that you'll lose lean mass or become "skinny fat" by just doing cardio. Honestly, I haven't lifted weights since my early 20's. I've run, done yoga, done martial arts for years... I had a DEXA scan done in 2004 at 29 years of age that showed I have 120 lbs of lean mass and I had one done a few weeks ago that showed the same 120 lbs of lean mass. I haven't lifted a single weight in that time and my diet has been all over the board, two pregnancies... not to mention 8 years have passed.

So... why is it that people are told not to do cardio only? If you already have a decent muscle base, why not just burn off the fat? I don't understand. It seems pretty hard to lose muscle... there was a time I wanted to.

two pregnancies - does that mean you have had small children around the house? that's weightlifting.

haha yep... I have a 6 year old and a 2 year old. I often have to squat to the ground while holding the 34lb 2 year old

Lisa294

BUMP

icemaiden17_uk

Just to stick my ore in!! I was doing Lots of cardio and lost loads of muscle mass! Now I do both that loss has slowed and I am hoping on Friday to see it stop! And then it can start going up!! Woo hoo!!

Also I have to agree that you are not really doing just cardio with all your activities!! I would've lost more muscle mass if I hadn't been doing Yoga as well!!

runnerchick69

Personally, I don't want to be a big muscled body builder, but I greatly prefer my higher muscle mass (and higher body fat) look to that of a lower muscle mass that many runners seem to have.

I'm the one in yellow. I prefer my arms and legs over the arms and legs of the two girls ahead of me. I'd love to be as fast as they are, because they cream my *kitten* in races. :embarassed: We're all in the same age group (35-39). They're not skinny fat. They have low body fat, but also a lower muscle mass.

And I'm not all that muscular, as you can see when relaxed in normal clothes. But I'm not anywhere near a "runner's build."

I'm a runner who loves muscle mass My weight is around 127 but I wear a size 0-2 because of the muscle I've built from running and now cycling. I've also gotten used to the higher body fat numbers, seems to go with the territory when you have a great deal of muscle! We've got some guys in our local running groups that look like they have skin on top of bone and that's about it! I have nice toned arms and am told runners legs and love them. I do use weights a couple of times a week but my trainer has me on lower weights and higher reps. I think you look great by the way!

In regards to the original post, I personally believe Yoga is strength training. It isn't my thing, I perfer weights but everyone has to do what works for them. I run, bike, spin and strength train and it's all good :happy:

Glucocorticoid

The reason you see that so many posts on MFP telling us that we will lose muscle if we do cardio only is because there is a large MFP population that comes to these forums from bodybuilding.com and/or other body building sites. You can even see the same catch phrases in many of their posts.

Of course you can keep muscle with cardio only. Muscles that are being worked regularly do not whither away, no matter how you work them.

Do you honestly think it's this simplistic? So people just lift weights for fun while in a deficit?

An hour of low intensity cardio won't usually cause problems, but let's take it to another extreme - three hours of high intensity cardio, done multiple times a week. As you go to a higher and higher states of intensities, you tend to recruit more type 2 muscle fibers while sending an "endurance signal" - this means the fibers need to adapt to the signal, which means becoming smaller. Combine that with a caloric deficit, and low protein intake, and this is bad news. Vaguely speaking, in that situation there is a higher likelihood of muscle loss, but even that will depend on various factors - to name some:
1. How overfat the individual is
2. Around workout nutrition and total daily caloric/macro intake
3. The rest of the training program (looking at frequency, volume, and intensity).
4. Genetics/gender
5. Other factors I'm overlooking at the moment

Of course, things get further complicated with the newbie effect. And when people are actually losing weight, even in the cases of muscle loss, the muscles hiding behind the fat become more apparent due to the accompanied fat loss, giving a more "toned" look, which adds on to the confusion. But none of this changes what I described above.

Yes, you can overdo cardio and eat a bad diet. You can also keep LBM with cardio only IF done properly and while eating a proper diet? Does that make it all better?

Sure, you can in certain situations. It will just depend on the factors I listed. Once you get extremely lean, cardio will not be enough in a significant deficit for most people. One will need a high tension muscle stimulus to optimally retain LBM (along with adequate protein intake and other requirements). Which is not to say certain amounts of cardio does not have it's benefits even in that situation - the two aren't mutually exclusive. But if hypothetically speaking, if you had to pick one, you would choose an adequate resistance program over cardio in that situation. (unless your goal happens to differ - i.e. you don't care about muscle loss or you are an endurance athlete)

lizziebeth1028

In my younger years I could do cardio all the time, I was a cardio machine!!! And I still maintained muscle tone and strength. Now that I'm in my 50's...that does not work for me. Too much cardio now makes me look haggard, tired ...and flabby (yuck). Now I need strength training/ weight lifting to maintain muscle!!!

So what works in your youth does not always translate to your latter years.

manospeed

I would like to see some scientific proof that you'll lose lean mass or become "skinny fat" by just doing cardio. Honestly, I haven't lifted weights since my early 20's. I've run, done yoga, done martial arts for years... I had a DEXA scan done in 2004 at 29 years of age that showed I have 120 lbs of lean mass and I had one done a few weeks ago that showed the same 120 lbs of lean mass. I haven't lifted a single weight in that time and my diet has been all over the board, two pregnancies... not to mention 8 years have passed.

So... why is it that people are told not to do cardio only? If you already have a decent muscle base, why not just burn off the fat? I don't understand. It seems pretty hard to lose muscle... there was a time I wanted to.

You don't need scientific proof. All you need is common sense and a pair of eyes. Look at all the marathon runners and cyclists in the World. Not one of them is muscular, but all of them are quite skinny almost like toothpicks. The body get's rid of things it does not need. If you stay in a bed for 3 months all your muscles will have become smaller because muscles which are not stimulated from lifting eventually disappear because the body doesn't need them. Muscles need more energy than other tissue. If the body doesn't need muscle it get's rid of them which also causes your metabolism to slow down as well.

Finally, once glycogen levels in your muscles have dropped during intense exercise the body will use whatever it finds to "feed" itself. In this case, 75% of calories burned come from fat stored in your body, while 25% comes from muscle.

This is the reason bodybuilders eat every 2.5 - 3 hours because they do not want to lose muscle tissue which is very hard to gain.

carld256

Did you actually read the study? If you did, you'd see how wrong that interpretation is.

Having read the study now, I don't see what you think is wrong about the site I quoted. The diet and endurance (cardio) group lost the most fat, 8% vs. 4.3% for the strength training group.

"Surprisingly, all dietary groups experienced similar reductions in body mass (−6.2, −6.8, and −7.0 kg for D, DE, and DES groups, respectively) and body composition (−5.8, −8.0, and −4.3% in D, DE, and DES groups, respectively),"

While the diet and endurance group gained lean body mass (+1.4 kg), the diet, exercise and strength training group lost fat-free mass (1.7kg or 3.7 lbs) just like the article I quoted said.

"whereas fat-free mass remained relatively constant (−0.1, +1.4, and −1.7 kg in D, DE, and DES groups, respectively) over the 12-wk period."

This study actually shows the opposite of what people citing it claim.

crisanderson27

In my younger years I could do cardio all the time, I was a cardio machine!!! And I still maintained muscle tone and strength. Now that I'm in my 50's...that does not work for me. Too much cardio now makes me look haggard, tired ...and flabby (yuck). Now I need strength training/ weight lifting to maintain muscle!!!

So what works in your youth does not always translate to your latter years.

This is because your body naturally produced more growth hormone when you were younger. This helps significantly with maintaining lean mass, regardless of the type of exercise. It is also significantly increased with strength training (at any age, though again...moreso when you're younger). Kenny and I have discussed this fact on her before.