*load nhanes
webuse nhanes2, clear

*generate a variable where all values = 0 (to make sure your function works)
gen test=0

*create a list of all variable names
ds //list all variable
local varlist `r(varlist)'
display "`varlist'"


*function to drop all variables that sum to 0
 foreach var of local varlist {
        sum `var',  meanonly
        if r(mean)==0 {
                drop `var'
         }
 }