How change $PATH for RStudio

I am trying to set my $PATH variable for RStudio. Somehow it just ignores the entry in my ~/.Renviron. I added this lines:

PATH=$PATH:/opt/R/arm64/gfortran/bin
R_MAX_VSIZE=100Gb

if I run Sys.getenv("PATH") it just shows my PATH without the addition I made. If I run Sys.getenv("R_MAX_VSIZE") it shows 100Gb, so the .Renviron file is recognized. What am I doing wrong here?