The next line of the article after that 40% quote:

> Carla Prado, a nutrition researcher in the Faculty of Agricultural, Life & Environmental Sciences and lead author on the commentary, explains this rate of muscle decline is significantly higher than what is typically observed with calorie-reduced diets or normal aging and could lead to a host of long-term health issues — including decreased immunity, increased risk of infections and poor wound healing.

The rather obvious problem is that these GLP1 agonists don't improve your diet. If you continue to eat a protein and nutrient deficient diet (which is probably a majority of Americans) with caloric restriction on top of that, that leads to excessive muscle loss that you wouldn't see in a weight loss diet. This normally doesn't happen without GLP1 agonists, because these diets are too difficult to stick to for most people. Those who stick to them usually turn to nutritious high satiety whole foods that help combat the negative effects of caloric restriction.

Losing weight without losing muscle mass is very hard. It requires extreme diets like a protein sparring modified fast where 80%+ of your calories are from lean protein while running a 50% caloric deficit. If this research is correct, then using GLP1 agonists shortcuts the feedback loops that make the diets hard to stick to, but they shift the tradeoffs from weight to overall nutrition.

"When a measure becomes a target, it ceases to be a good measure" and all that.

See the actual research article:

https://www.sciencedirect.com/science/article/pii/S2452302X2...

This study on mice was suggested by a previous publication:

https://www.thelancet.com/journals/landia/article/PIIS2213-8...

where it had been noticed that in humans "the muscle loss with these medications (as indicated by decreases in fat-free mass [FFM]) ranges from 25% to 39% of the total weight lost over 36–72 weeks", in comparison with muscle loss of only 10% to 30% when the weight is lost just by eating less, without semaglutide.

So with semaglutide, a larger fraction of the weight loss affects muscles than when the same weight is lost by traditional means.

While for other muscles the loss of mass may not be so important, the fact that at least in mice the loss also affects the heart is worrisome and it certainly warrants further studies.

I don't have it at hand [edit: [0]] but there are a number of studies showing exercice had more health impact than weight loss (you can combine both of course, but just losing weight has less benefits)

As you point out, losing muscle is common in a diet, and the researchers are well aware of it. Their point was that this aspect is not pushed enough and is drowned by the losing weight part.

From the paper:

> Dismissing the importance of muscle loss can create a disconnect between patients' increased awareness of muscle and the role it plays in health, and clinicians who downplay these concerns, affecting adherence to and the development of optimised treatment plans.

[0] https://journals.lww.com/acsm-csmr/Fulltext/2019/08000/Effec...

For the "Fitness Versus Fatness" part for instance

Interestingly, when I was part of a weight loss diet study at my local university I actually gained muscle whilst losing weight.

I had multiple full body dexascans during the programme.

I didn’t change my exercise routine at all. I wasn’t hitting the gym or doing weights, just my usual basic cardio.

And I gained muscle and lost ~10kilos in weight.

It wasn’t much muscle, but the amount of muscle was higher than before.

The article does dissect the difference between weight loss drugs and dieting in general. Where they found that muscle mass loss was higher in those that took the drug as opposed to those who followed a calorie restricted diet.

To your point, the drug is absolutely to do with it if by taking the drug people need to be more mindful of the types of food they eat, if they have a smaller window to consume nutrients.

It is most certainly a contributor and for some who may not exercise like you, or consume an appropriate level of protein this research may show that those taking the drug need to focus on a more protein right diet.

Biology is super complicated with lots of surprising dependencies between different biological pathways. So it is possible. That said, I am skeptical as well. For example, if the body sheds 15% of its weight, does the heart naturally shrink by 15% as well? With so many people taking these drugs, there is enough data to begin to profile the rare risks of these drugs in humans (the clinical trials would have found any of the obvious risks)

Just curious, does your appetite come back whence you cut off the meds?

The only reason I want to lose weight is to eat more freely, won't be useful if I lose my appetite too.

god... 133kg down to 88kg, that's like a dream to me. Years of trying to get under 100 by 'traditional' calorie restriction diet & exercise.

So it smells like bullshit because of your personal anecdote? Or because some scientific evidence or experience you have?

Yeah, folks don't like thinking that obese people have a lot of muscle needed to move around. And losing weight is losing all weight.