Diet and exercise methods don't[1] work for most people, for loss and especially for healthy weight maintenance.
With extreme levels of direct, personal involvement by multiple professionals (which is what rich people / celebrities have historically used, and variations of which have been studied by researchers) the efficacy level reaches "sort-of OK, but still not great". That's crazy-expensive, though, so not a realistic solution for the masses, plus the results are still pretty lackluster despite the cost.
[1] Could, hypothetically, yes "CICO", technically anyone could lose weight, but they in fact do not work when applied in the real world, statistically speaking.
With extreme levels of direct, personal involvement by multiple professionals (which is what rich people / celebrities have historically used, and variations of which have been studied by researchers) the efficacy level reaches "sort-of OK, but still not great". That's crazy-expensive, though, so not a realistic solution for the masses, plus the results are still pretty lackluster despite the cost.
[1] Could, hypothetically, yes "CICO", technically anyone could lose weight, but they in fact do not work when applied in the real world, statistically speaking.