Your analogy is false.

If you opt for it, then yes of course, abstinence-only sex education is a sure way to stop ten pregnancy.

Similarly, if you opt to change your lifestyle and start living healthier, and follow through, it will work.

If someone tries to force you, of course it will fail (in both of these cases). There is no way to stop someone else from being fat. We can only change ourselves.

It's a lifestyle, the optimal basic lifestyle, the one were you don't shorten your life/healthspan by decades. It's how thing were intended to be really.

It's funny how proposing an healthy diet is unrealistic and watching fatties eat themselves to death is the new normal, complete value inversion and looser mentality

Long enough in this case meaning forever.

Behavioural changes work, the issue is that most people don't actually change their behaviour.