When you are weight training to change your body composition your goal should be to overload your muscles with a heavy resistance. This is best achieved by using a weight that you can complete at least 4 reps on your own but no more than 6 reps. (Always with good control and execution of each rep.)
If you are not challenging yourself with your weight selection (this goes for women too) you will be limiting your results.
People will sometimes look at a Max-OT workout and see I only do 4 sets for biceps for example and will say to themselves there is no way that is enough. Then they will try it for themselves and tell me it doesn't "feel" like they did anything. When I get that answer I know that the person's intensity level was not where it needs to be because if you do 4 sets with high intensity I guarantee you will not want to do the 5th set.
When you are striving to build muscle (again this is for women too because there should always be a strong muscle building component to each workout if you want to change body composition) you need to continually overload the muscle with a heavy resistance NOT fatigue the muscle with countless high rep sets.
One way to improve your intensity is by working to better your numbers each workout. You should try to either increase weight on at least one exercise or achieve more reps than the week before. A training journal is a helpful tool to ensure that you never go backwards with your weight selection because you will have a detailed account of your progress at your fingertips.
Remember, to best change your body composition focus on the intensity of your workouts NOT the duration. Keep a journal and strive to better your numbers each workout.