hi doma,
1. he makes a claim about what his doctors said.
2. he was overweight and his knees and back were disfunctional.
3. he did yoga and lost weight.
3. his knees and back turned out to be able to support him when he was 150lbs.
5. you throw away modern medicine because of point 1.
there's no magic here. knees and backs are well-known load-sensitive parts of the body. i know several people who have managed to change the functioning of their knees and back via weight loss.
you want me to believe that this guy is special. i say he is not untypical.
i don't believe an overweight person when he says his doctors omitted to advise him to lose weight.
but could a doctor have predicted with accuracy that his joints would support him at a weight of 150lbs? nope. they may have only borne the load at 80lbs.
the only way to test such a theory was by losing the weight.
if you think a nice anecdote about a guy who lost weight makes a strong argument against the value of modern medicine, i think you are fooling yourself. i say it is physiology and exercise that made the difference.
but if you could provide double-blind trials showing that medicine fails to produce the results it says it will, then you will have a tremendous power of persuasion at your fingertips.