If you're a person who holds a grudge and feels betrayed about something like that, then my guess is that your friend and your in-laws didn't share their WLS "secret" with you because they were afraid of hurting your tender feelings by suggesting that you're morbidly obese and should have bariatric surgery to deal with it.
I see people every day (strangers, friends, acquaintances, coworkers, etc.) who I think could benefit from WLS, but it would be mighty intrusive and presumptuous of me to approach them and say, "You really need to consider bariatric surgery for your weight problem." Their weight is their own business, not mine.