When you equip Items with health boost stats(I'm not sure if any of the happens with the other stats) and simultaneously giving them a health boost effect.
A leather cap with health stat boost of 40, the color red and a custom name:
A Health boost effect for just a few seconds:
/effect @p 6 30 6 true
A photo of this weird death state whilst active AND a world built with the setup because I couldn't recreate this it's this exact setup.