Mechanick, J. (2013). “What If” Being Overweight was Good For You? Endocrine Practice, 19(1), 166–168.

https://doi.org/10.4158/endp.19.1.50042678317gx698

The evidence that being overweight is healthier is a bit dubious, but the evidence that having a "normal" BMI is healthier than "overweight" is nonexistent.