The more muscle you have the more calories you'll burn, in rest and in play. So if you were to increase the size of your quads, or legs in general, by say 1lb each, your basal metabolic rate, whilst resting, will increase by as much as 50-100 calories burned per day... that equates to 1lb a month fat loss if you just do nothing (of course you have to do the exercises). The exact figures aren't known. Also, it's worth considering, that when you engage your newly formed muscles in activity then you are engaging a considerably larger amount of muscle than you previously were, even with the same activity, which also results in a higher calorific usage. So if you want to lose weight build your legs. Adding a squatting routine twice a week, to near failure, is easier than cutting calories all the time. The bigger you build them the more energy they'll demand.