Weight-loss drug found to shrink muscle in mice, human cells

Yep. I started resistance training 5x a week about a month in on tirzepatide and even with a severely restricted caloric intake (I just can't eat enough), I've gained LBM.

How did you measure the increase in LBM? This requires very advanced technical equipment. My suspicion is that you have noticed an increase in muscle volume and assumed it to be an increase in muscle mass. Those are largely due to water retention and increased blood flow. They revert quite quickly after you stop exercising for about a week.

DEXA scans are accurate and readily available in most cities for about $100. Just do it quarterly or whatever.

I am getting regular DEXA scans

Does ability to lift weight also decrease in about a week? I was recently out of town for over two weeks and came back with the ability to lift roughly the same amount I was able to prior to leaving.

My DEXA scans seem roughly correlated with the amount of weight I can do in my regular sets, which has increased about 50-70% depending on which muscle group you are talking about.

This is with heavy resistance training 3 times a week and Pilates once a week.

A good portion of the strength related to any specific lift is CNS adaptation up until a certain point (and most new lifters won't hit that threshold for quite some time), so strength on a lift you've been doing regularly isn't necessarily a good indicator. Building muscle will of course increase your strength too, but I've doubled my squat since getting back into lifting while certainly not doubling the muscle mass of the respective muscles.

Fair enough. I didn’t mean a 1:1 correlation in 50% on a Dexa means 50% more strength, just would expect my lifting ability to go down if I lost muscle mass (or if it were water weight to begin with). Neither have decreased much if at all during breaks, so I’m fairly convinced it’s “real” so to speak.

Looking through my weightlifting app my best tracked exercise (leg press) increased about 250% from start with a 60% (roughly, speaking from memory) increase in lean muscle mass as measured by a DEXA scan. If I remember when back from dog walks tonight I’ll update that with a real number off the actual data.

I was a total newb at lifting though, so those early gains came quite quickly.

I am curious as this is a concern I have for long term health.