Any person whose objective is to lose weight should also add to your routine a weight training. The reason is simple: in addition to improving muscle tone to prevent injuries, increase the amount of muscle, something that will help us to burn more calories throughout the day.
Weight loss is focused primarily on getting a negative energy balance, i.e., spend more energy that we eat. If we add a weight training to the aerobic we contribute to increase the number of calories we burn a day, in addition to those we spend itself in this exercise.
To gain that muscle mass with the weight training you get to burn more fat, so long term (3-4 months), much of the weight that is lost is fat-based Thanks to greater muscle volume, which is what we want.
The problem of putting weights in the weight loss workout is that at the beginning the scale does not fall, now than what we lose on one side of fat we gain it in muscle, but it is somewhat profitable long term. If they put aside the weights in a fat training part of the lost weight is muscle, something that does not interest for risk of injury posed by losing tissue active metabolicamente.
Is of course not do a weight training with the intention of winning the greatest possible muscle mass, but toning the muscles first to adapt to the workouts and make them grow a little after getting more intensity.