Are you suggesting that the excess weight deemed to be obesity is from plastics and not fat? And that both the toxicity of the plastic and its distribution in the body mimics what we would expect fat to do?
It seems that regardless it would be very noticeable to doctors performing physicals if many of their obese patients were actually stuffed with microplastics instead. I'm sure you could find positive support for this in the medical literature if it had a modicum of truth to it.