Indeed. The fact that they (the drug’s sponsors) didn’t look at how much of the weight lost during the RCT was lean mass is very damning.

To your point, we know lifting weights specifically is crucial for maintaining bone mineral density. I wonder if there’s a correlation between loss of lean mass and reduced bone mineral density.

Evidence is mixed on weight lifting and bone density. Some studies see no benefit at all. The idea that it is "crucial" isn't supported by any evidence at all. Most people have bone density that is fine without any weight lifting.

On the other hand the evidence on running and bone density is very consistent.

So for good bone density you need to pursue a high impact sport that might destroy your joints? Unfortunate if true!

There is a lot of evidence that high impact sports like running actually improve joint health. Especially if they practice appropriate resting and nutrition. I suspect that a lot of the injuries we associate with high impact activities are from people who have lost conditioning from inactivity, attempting to resume exercise without knowing their new limits.

https://www.nm.org/healthbeat/healthy-tips/fitness/is-runnin...

same idea as building a callous on your hands or feet. lots of use tends to toughen your joints.

Try taking a look at high intensity resistance training. It's the weight lifting equivalent to high intensity interval training. It's very effective, and it's low impact relative to the amount of time spent exercising.

You are incorrect. There is a consensus among scientists who study this subject that /skeletal/ muscle mass is directly associated with bone density. There are specific arguments and disagreements about what exercise is most beneficial for increasing overall skeletal muscle mass index efficiently, but the relationship between skeletal muscle mass, blood flow and nutrient distributions, the downstream effects on hormone regulation systems, and how all of those improve bone density are very well studied.

Neither you or the above commenter have provided sources.

AFAIK resistance training would beat aerobic sport (for this problem); the correlation is right in the headline.

https://pubmed.ncbi.nlm.nih.gov/31797417/

While I'm not sure about the connection between weight lifting and bone density, I do know that inactivity is a major cause of injury and lost physical fitness. A person who is obese is getting that exercise just by existing. Every time they stand up, lift an arm, bend over, or walk across the room, they are engaging in more exercise than a low body weight person does in the gym. Once that weight is gone, they will need to increase activity levels.

I would be surprised if the activity of moving you overweight body around could be classified as resistance exercise when it comes to any of the positive adaptation usually elicited by lifting bb

I imagine if you lifted bar bells 24/7 it would be way less healthy. I know that wearable weights are not recommended because it can cause health problems and injuries. I like this video by Phil Gaimon. Stuff like walking, standing, balancing and getting on his bike are much more difficult.

https://www.youtube.com/watch?v=Y6W2Hmy0Lzo

I don't understand why your first claim supports the second. I agree obese people are very muscular. But since you won't need so much muscle and bone when you weigh less, why is it important to exercise any more than it is generally?

So that the body isn't burning too much muscle in an attempt to preserve the fat

As you lose weight, you need to adapt to your changing body. You will lose a lot of muscle in the process which is okay! However, all that exercise you got from just standing and walking normally will go away too. Maintaining condition will require intentional effort, otherwise you will start to see injuries. Think of it like physical therapy while recovering from an illness.

There have been some studies that show that muscle loss is disapportionally higher than fat loss, which would lead to worse body composition after losing weight.

If I remember correctly, that happens because when on calorific deficit, by default people reduce their activity - this is the instinctual response. Body responds by losing muscular mass as energetically it is costlier to maintain than fat. This is why it is important to maintain or even increase the activity while losing weight.

This would surprise me since the primary reason a body stores excess fat is to be used for energy when needed. Then, the moment of need arrives and the body burns mostly muscle? Citation would be appreciated.

I always think of it as the difference between starving in a cave waiting for winter to end and starving while attempting to hunt down food in the summer. In the winter, reducing energy expenditure is important so you lose muscle first. In the summer it's more important to maintain condition so you can fight off competition and cultivate food sources.

By hunkering down on the couch and just losing weight you get the winter scenario. By exercising while you lose weight you get the summer scenario.

Makes sense really. The fat stores will go a longer way with less muscle. I imagine that would work brilliantly during the cold winter months living in a cave, where theres less reason to move much. Unfortunately, this is dysfunctional in the developed world.