Stata's mixed command*- adjusting for confounding variables

Hello,
I am trying to run a linear mixed model to test the within-subject difference in activity behaviours (eg sleep, sedentary time etc) between 2 different timepoints (school vs. holidays) and I want to adjust for relevant confounding variable (ie sex, ses, and bmi).
When I run the following command with no adjustment: (mixed genesed || wave: || schoolid: || id I get the same result for sedentary time (genesed) as I do when I include the confounding variables (mixed genesed i.time_new z_sep_composite t1_bmi_zscore t1_ageatanthropassessment i.sex_new || wave: || schoolid: || id. What am I doing wrong?