In what world is "eat less" as easy or effective as getting a shot?

Losing weight is quite hard and keeping it off is next to impossible, given that very few succeed.

In case you're serious, you can read this. https://slimemoldtimemold.com/2021/07/11/a-chemical-hunger-p...

Vaccination is used for prevention. Eating less is also prevention (or would you rather prefer "not eating a lot"?)... from getting obese. Once you are obese, eating less also could serve as a treatment; you lose weight.

Maybe, but it's not easy at all unlike getting a vaccine. Otherwise we wouldn't be seeing a global epidemic of obesity. One has to eat less for a very long amount of time.

Are obese people starting off as obese though? I would think that they have to eat a lot to become obese to begin with, which suggests that eating less prevents one from getting obese[1].

Eating less is both prevention and treatment.

[1] Excluding metabolic disorders