[Retric]

There’s negative cardiovascular effects from excess muscle just as with excess fat.

Normally that’s offset by the health effects of the exercise required to gain and maintain them as well as the lack of medical conditions that prevent exercise etc. But a fat person losing weight should inherently lose muscle mass long term assuming no changes to lifestyle.

[cthalupa]

This is one of those statements that is technically true but not particularly relevant. Obese people are almost never at a level of lean body mass that they would overall be at a good amount of muscle even for a healthy total weight, and rapid weight loss has consistently been shown in studies to reduce more lean body mass than slower weight loss.

Getting to the same level of additional weight from muscles as there is from fat is also incredibly difficult. The average 5'8 person not utilizing AAS would take years of dedicated training, dialed in diet and recovery, etc., to get to 200lb at 15% bodyfat. People get there much faster and much easier putting on fat.

[Retric]

What’s relevant is subjective. I’ll agree it’s far from as important as obesity, but the point is some of this adaptation is good.

As to loss of muscle mass from rapid weight loss, that’s very true but slightly overstated as regaining muscle can occur ~10x as fast as it takes to grow it in the first place. Someone without a significant calorie deficit barring nutritional deficiency or other impediment will regain whatever muscle mass is required for their lifestyle quite quickly. However, people don’t train with weighted vests as among other things it targets the wrong muscle groups.

[cthalupa]

>muscle mass is required for their lifestyle

The problem here is that the overwhelming majority of people that need GLP-1s have lifestyles that are not conducive to health and have less muscle mass than would be healthy to begin with.

Which is what has me so confounded by this claims - these people already have less muscle than they should for optimal health. Losing any is a significant issue. And without lifestyle intervention, they're not going to regain any of that lost muscle.

GLP-1 drugs are phenomenal and a huge win for health outcomes. But that doesn't mean we shouldn't be telling people the truth about their downsides and what they need to do to counteract them.

[Retric]

Let’s ignore GLP-1, and assume an individual slowly dieted to that exact same weight. What’s going to happen over the following year(s) is their lifestyle causes identical muscle loss.

In that context is this a long term downside of GLP-1 or their lifestyle?

Treating lean muscle mass as an inherent good makes sense when it’s adapted to a person’s current lifestyle. It doesn’t make sense when it’s a temporary situation.

[cthalupa]

False dichotomy - much of the muscle loss happens because of the rapid weight loss. If you diet more slowly and are not at very high levels of relative musculature you’re not going to lose nearly as much even in the long run, at least prior to advanced age. The newly skinny person might lose some muscle mass on their legs if they dieted down slowly, but it is significantly less likely that they will lose all of the other body-wide muscle mass that they do with rapid weight loss.

Your body will hold on to a surprising amount of muscle. Even people that take PEDs can drop back down to natural testosterone levels and keep ~80% of their gains in the long term. (Actual gains, not the temporary glycogen and intra-muscular water retention that you see with some compounds on cycle.) It takes significant effort for them, but they’re trying to hold on to supraphysiological levels, vs. someone who is trying to hold on to what is already on the lower end of the physiological range.

[Retric]

> False dichotomy

No, you’re looking at the short term effects on a largely irrelevant metric (volume) while ignoring the underlying mechanisms at play.

> Your body will hold on to a surprising amount of muscle.

It’s only surprising if you ignore what going on at the cellular level. Gaining fat or muscle eventually involves gaining new cells and structures like capillaries not just increased the volume of existing cells. This is a really slow process in muscle, but those new cells stick around and can rapidly adapt to stimulus as long as you have a sufficient diet.

So yes in rapid weight loss your individual muscles cells become smaller and less capable but that’s very quick to recover. Longer term, you’ll hit the exact same homeostasis point based on stimulus and long term diet.

PS: If this seems like voodoo magic it’s simply a very old evolutionary response to starvation that predates hominid development. Being able to fairly rapidly lower energy expenditure over say winter and then recover is a major advantage.

[obvi8]

I was looking for this comment! Not a doctor, but as I understand it muscle is roughly equivalent to fat as far as your heart’s workload is concerned. I thought I also read that muscle movement helps with blood return.

[genewitch]

Muscle movement is also necessary for the limbic system to function.

[Retric]

Limbic system is unrelated to muscle movement.

Movement is required for the lymphatic system to function, excess muscle volume doesn’t help.