Are there cases where it has no effect even if you get hit by Maunzaro?

I am worried because I have gained a lot of weight lately due to a heavy workload and irregular lifestyle. My stomach, in particular, bulges significantly even after eating just a little, so I became interested in Maunzaro.

I became interested and looked it up after seeing videos of celebrities recently getting this injection and seeing great results. However, I actually saw an article stating that the effects of Maunzaro don't last and that the weight comes back. Is it really true that it isn't very effective? I am curious about the side effects.