lifting weights won't add mass to you if you keep your calorie intake down. building mass requires calories, regardless of whether you're building muscle or fat. you can lift weights all day and you won't gain a bit of muscle if you don't take in enough calories. lift 3 days a week and do cardio 2 days a week or visa versa. also, running sprints or any other type of high intensity cardio will burn more fat than distance training, so try alternating between the two.
"No, Mama. You can bet your sweet ass and half a titty whoever put that hit on you already got the cops in their back pocket." ~Black Dynamite