I'm losing muscle!!!!

Autocorrect strikes again...

Too much cardio and not enough lifting. And HEAVY lifting....high reps and light weight won't do much if you're trying to gain lean muscle mass. Plus, up your protein intake as others have mentioned.

With extensive endurance training you will lose a lot of muscle mass. It comes with the territory...

I expected to lose some muscle but 43% of my weight loss? With such a low deficit and the amount of protein I'm consuming, combined with some strength training this just doesn't seem right. Am I missing some sort of hormone or is there any other possible explanation?

Actually I was going to mention this very fact...your age suggests you might be in some stage of the menopause..so hormones may play a part..certainly worth getting this checked out.

That's why I get my BF% checked with the Bod Pod. It is on par with hydrostatic weighing.

Neither of those methods are terribly accurate. DEXA scan is the most accurate, and even that has problems.

I started tracking my body fat% back in the beginning of June. Since then I've lost 13 more pounds but only 7.32 lbs is fat loss; the other 5.68 lbs is lean body mass (muscle). I'm only losing about 2 lbs a month so I'm not starving myself. I am doing some weight training about twice a week. Although, I admit I'm not always consistent. But why am I losing so much lean mass? I'm getting very frustrated being stuck at 26+ % body fat. BTW, I am verifying my BF% by having the Bod Pod done every 3 months. What in the heck is going on?

While you will lose lean muscle along with fat, to retain muscle you do need to really challenge it. That's why when I hear people using 5lb weight for dumbell bench presses I have to intercede and tell them that it's not enough because that doesn't challenge their actual strength. And it's BS when they say "but it's heavy for me", yet carrying a 5lb grocery bag or a 5lb purse isn't.
2 things. Bump your weights up and be CONSISTENT.
Understand the more lean muscle you lose the lower you metabolic rate will go and the slower your weight loss journey will go too.






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

I am lifting pretty heavy...can only do about 10-12 reps of any given weight. Once I can do more than that I bump up the weight. I do full body - but sometimes I leave out the legs if I have a long run the next day.

Lower your reps to 6 and as much weight as you can handle. The last rep should be super hard.


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

I currently weigh 130 lbs. My body fat % is 26.6. I do cardio 6 days a week. I run about 35-40 miles a week currently (training for a marathon). I also usually bike 2-3 times a week. But I eat back ALL of my exercise calories. I am NOT starving myself. This is so frustrating. I love to compete in athletics but dragging around this extra body fat is getting old.

Okay this would explain it now. Long endurance cardio catabolizes muscle. It's part of the territory. Regardless of how well you eat and even if you train hard with weights, it's almost inevitable that you will lose lean muscle. That's why the physiques of sprinters and long distance runners are so different.
Unfortunately you have to choose what you want to do and if it's a marathon, then you're going to lose lean muscle because that's usually how it works.


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

If you don't eat enough your body thinks it is starving, and preserves fat, while getting rid of muscle (because fat takes so much less energy to maintain). That's the main reason why slow weightloss is so much more effective in the long run than losing super quickly. Obviously you are doing great, but you may need a few more calories.

For every additional pound of lean muscle mass on your body, you will burn about 35 to 50 additional calories per day (from a study done at Tufts University). That adds to a LOT of calories over the course of a month.

I hope this helps! Make sure you are getting enough protein and calories. If you have any questions message me/add me as a friend!

Okay this would explain it now. Long endurance cardio catabolizes muscle. It's part of the territory. Regardless of how well you eat and even if you train hard with weights, it's almost inevitable that you will lose lean muscle.

Ok, I guess I'll have to accept the muscle loss but with all the cardio why am I not seeing a greater reduction in BF% On June 1st I was at 29.3% body fat. And now, almost 6 months later I'm only down to 26.6%

"Normal" body fat for a woman is between 25-31%. Because you're in the normal (or acceptable) range, it's slower going, as you don't have a lot of excess fat to lose, so your body hangs on to it more. Top female athletes have around 15-20% body fat. You aren't losing a lot of body fat, because you don't have much to lose.

Also, excessive cardio (which marathon training would be considered "excessive" for weight loss purposes) leads to slower fat loss, as your body doesn't burn that much fat during cardio before it switches over to catabolizing muscle. That's why most generic cardio programs are suggested to be about 30-60 minutes, any more than that generally leads to more muscle loss, and less fat burning, and has no real weight loss effect. Not trying to talk you out of running, just so you know, I love to run, just trying to explain how things work. :drinker: