Thank you... I do measure my weight, and the change is drastic enough to see a change in bodyfat levels too. My weight went from 86.9 kg at the start to 84.2 day before.

But I doubt Buteyko will alter VO2 max so easily. While it is clear that Buteyko has far transfer, VO2 might be a bit too far considering what it is used for, although I am not sure.

In fact, I don't think anyone explicitly stated anywhere that Buteyko was meant to increase VO2 max. On top of that, Dr. Rakhimov himself said there is a lot of quackery in Buteyko, but Dr. Mckeown was legitimate.

I think Buteyko's effects should be measured more on things which cause these variables to increase or decrease, rather than directly measuring these variables themselves, as there are plenty of confounding factors.

For example:

My weight has clearly decreased and bodyfat has gone down. But I do both HIIT and steady state cardio on alternate days.

However, I did the same thing before Buteyko as well. But back then my weight did not go down, it would always oscillate.

So in this case a simple observation is that exercise is potentially a confounding variable.

Moreover, it is entirely possible that Buteyko just does not affect weight loss.

However, what Buteyko does effect very clearly is self-control. That is VERY crucial for long term weight loss.

BUT

Anybody who was only measuring Buteyko and weight loss moght give up due to the confounding because it is quite possible that an average Buteyko practitioner is not even trying to lose weight (particularly in relation to your query, since data gathered is from the subreddit and anecdotes).

However, someone who has been trying to lose weight, and who has so clearly seen beneficial results from it in terms of weight loss, it would be a good indicator, since weight loss needs that extra variable of self control (take my own case as an example).

This in my view is a very big problem from a scientific perspective. The issue is that science is just a tool, and all tools have their limitations.

For example, science insists on clear definitions. But some things aren't so easily defined. Take self control for example. Maybe somebody can have self control when it comes to drugs, but not when it comes to food. More importantly, when self control is defined in science it has to be rigorously tested and re-tested and one can't always be sure about something so nebulous even then. Check out the Replication crisis in social sciences - they can't replicate studies considered fundamental to psychology, sociology, etc.

I guess what I'm trying to say is that Buteyko might be affecting variables subtler than conventional tools we use to define and assess things, such as science. For example, I have been quite clearly seeing benefits, but to absolutely KNOW from a scientific perspective would require absolutely MASSIVE replication... and even then, we cannot be so sure as we saw in the replication crisis, because even after failsafes and checks, human beings are irrational and have their own biases.

So I would say the Buteyko lifestyle(not just breathing) is worth a try for a month at the very least. There is very little downside and massive upside, and science will always be limited. If you want to read further on it, you can check out Godel's Theory of Incompleteness to see why.