i use to be 145-148 when i first started working out. i went up to 160 but i was on vacation for almost 3 weeks with no excercise. when i came back, i weighed in at 155. then as the days go by, i went down to 150. wtf? am i losing muscle or fat? i still got fat to lose but i'm afraid it's the muscles that's going away. the only thing i can think of that i'm doing more is running 2 miles instead of 1 and doing lighter weight. could this cause the weight lost?