Might be a stupid question

issiahs

So this is basically the opposite of the “I gained weight, did I just gain muscle” trope. Is it possible to lose weight and basically only lose muscle? Or is it that the body only loses muscle once a deficit is too large? I’m asking mostly out of curiosity and not really from any personal experience. I got to thinking about it and kind of just want to know the facts behind it.

ccrdragon

I don't think so. The body uses both stored protein and stored fat for energy (as well as glucose, although that is used mainly for brain activity and to fuel exercise). The amount of stored protein (i.e. muscle) that would be used would depend mostly on protein intake - are you eating enough to sustain current muscles/needs or not. The preferred energy source when you are resting is stored fat along with a small amount of protein to rebuild tissues that have been damaged during the course of the day (yes, this is an on-going process and happens even when you are not performing deliberate exercise).

steveko89

Off the cuff, I think the most likely scenario where losing only muscle would occur would be in a very sedentary person, not doing resistance training, with an already low body fat percentage, on a steep deficit. I could be entirely off but that's what makes the most logical sense to me. Curious what others have to say.

DebLaBounty

My experience was I set a goal on MFP to lose at a rate of two pounds a week. I lost 30 pounds in five months. Despite lifting weights, I lost muscle mass in my arms. I should have tried a slower rate of loss, maybe a pound a week.

RoxieDawn

Most all of us have enough body fat so we won't lose muscle like you are talking about, but you will lose some and how much depends on if we are or are not careful in our weight loss and doing all things we can to minimize that.

In the case when we are not doing those things we will lose muscle when the the calorie deficit is too aggressive, carbs are low, when there is not enough adequate protein and there is no resistance training or enough stimulus to our muscles to tell our body the muscle is still useful.

And remember muscle is metabolic, we need to fuel to maintain our muscle mass. When not enough of the above, we start running running out of needed fuel for our body so it it will tap into muscle to use for energy.

PAV8888

Steep deficit, how long the deficit has been applied, lack of sufficient fat to support the size of the deficit, insufficient available protein especially when paired with inadequate carbs, lack of muscle stimuli, and gender will all affect the fat to lean mass ratio. So your ratio will change as you lose or gain weight.

I note that lean mass includes more than muscle mass (in fact most of lean mass is not muscle mass). Similarly, muscle mass is only a fraction of your body's lean mass, so any and all of it is precious

You will lose and gain both when your weight changes. With your actions you can influence but you cannot control what gets gained or lost.

Unfortunately most common methods of measuring body composition... suck. The not so common ones... suck less. A trained human eyeball... sucks about the same.