"Showing up to the gym 3x a week" is also quite a lazy prescription. That doesn't even actually take exercise into account, nevermind diet.

Also, "weight loss" is a lazy metric for fitness success. Body fat %, for most, would be better, just as one example.

Plus, in this case, taking cold showers could be completely supplemental to a real plan. If nothing else, you would increase your self-discipline.

I do agree with you in the sense that people (in general) are susceptible to exercise fads, but I don't think HN is more than average. Hackers are curious, though - and so you get the interest in the off-beat stuff.