It depends how you define "short period of time". When I started, I lost 40kg in a matter of 5 months. Is that short? If you develop a tolerance to the product, then it doesn't protect you long term from gaining back weight, combined with you losing the option to do a rapid descent.
I am not saying that those variations are great from a health point of view, but they are certainly not as bad as staying obese.
Yeah that's quite short. Healthy weight loss is typically in the ~.5-1 kg/week, while this is an extended period at 2-4x that rate. The effect that will have will largely depend on what your starting weight is, but unless you're starting significantly north of 140kg, it seems like the amount of muscle (and maybe bone density?) loss would be pretty severe.
I am not saying that those variations are great from a health point of view, but they are certainly not as bad as staying obese.