question for endomourphs

i was told by a trainer that for an endomourph which is what i am that i should do one week light weight high reps from 10 to 12 reps and then the next week low reps heavy weight the next to change up things..... im new to this and i gain weight easy and my goal is to lose fat and i was wondering is 5 days a week 30 to 40 minutes of low intensity on the treadmill is to much or whats a good cardio program for endomourphs? any info would be very helpful .