How Would Weight Gain Before Umbilical Hernia Surgery With Mesh Repair Affect The Risk Or Outcome?

Hi, I have an umbilical hernia in my belly button believe for long time but just figure out after a ct scan study for some other reason year and half before so far I don't have big problem while my BMI is 20.50 or 21 with my height .I am thinking to do the surgery and preparing for it .But I am worrying about my mesh repair at the same time if I gain some weight before hernia repair how risky would be that because I looks too skinny that the reason me to put some weight into my body.will be appreciated if anybody give some right direction.
Thanks.