What does that mean, preventing stress adaptations? Does it mean that the body wouldn’t get stronger in training ?

Right. Some of these potential longevity interventions seem to have a catabolic effect. Not a problem if you're a mouse living in a safe, flat lab cage. But problematic for an elderly human at risk of falling down the stairs and breaking a hip due to sarcopenia.

Is it strong enough to actually cause that, or is it the kind of thing nonathletes won't notice?

Or is the life extension effect too subtle to be relevant at all outside a flat mousecage?

It's just a general trend. The strength of the catabolic effect will depend on the specific intervention and dose. The risk is greatest for non-athletes because they tend to be weaker to start with and more likely to experience disabling falls as they age.

That is really interesting. I hadn't heard that, but it makes a lot of sense.

There is some evidence that "aerobic exercise" itself produces an equivalent baseline energy deficit without the performance downside.

This guy[0] studies total average energy expenditure over time and demonstrates that an athlete undertaking intense regular exercise uses marginally more energy over time than someone sitting on a couch all day. The hypothesis being that the athlete is conserving energy by down-regulating baseline metabolic and inflammatory processes when at rest.

Disappointing news for "exercise causes dramatic weight loss" but encouraging news for "exercise is anti-cancer" (a correlation demonstrated many times I believe).

[0] https://www.science.org/content/article/scientist-busts-myth...

I have seen this study before, but I can't see how this gentleman's work disproves the huge body of health and fitness research that comes before it. It's an interesting outcome for sure, but the idea that it suggests exercise is a bad weight loss tool doesn't seem to reflect reality. The long term outcome of exercise is a changed body composition, which itself can contribute to changing metabolic rates.

I think it points to an interesting insight, something we have yet to uncover perhaps, but I don't think it disproves that exercise spends energy. Maybe all it's really proving is that we are very efficient at the chosen type of exercise in the study.

Exercise causes weight loss only in that as you want to get more fit you start watching what you eat, quality and quantity, more carefully.

As a lifelong runner I know I only burn 80 calories or less per mile, that's nothing.

However exercise does things that no supplement or drug can do, proper AMPK and cAMP activation, endorphin and endocannabinoid release.

I have just gotten my resting heart rate back down to pre-quarantine levels. I don’t know how many days I shaved off my lifespan from all that sitting around, but I’m a little bitter about it.