Just joined need advice.

If you add in weight training with cardio you will see results a lot quicker. I did Jillian Michaels and from August to November I lost 17 inches over all and 15lbs. I dropped two dress sizes as well. If you do cardio alone you will lose weight but your body won't change as quickly.

everyone's body responds a little bit differently to exercise, but what kelly said is typically true across the board.

if you're overly concerned with the number on the scale, you'll be likely to get frustrated when you start weight training, because you may not lose as quickly at first (since your muscles may retain fluid for the first several weeks as they're not used to having to repair themselves).

however, if you're more concerned with clothing size and what you see in the mirror (that's a good way to be--because now you're considering yourself in the same manner that others consider you), a combination of weight training and cardio is best because you'll lose inches and sizes and see more muscle definition far more quickly, which is what really helps others to start to notice a change in you

plus, if you start weight training now, you'll retain more lean body mass as you lose weight, which will keep your metabolism humming and really benefit you long-term.

Here is a study that was recently done about losing weight that my personal trainer discussed with me. The group who just did cardio had the best results than the group that just lifted weights and the group that did a combination of both. Hope this helps.

http://www.acefitness.org/expert-insight-article/29/3043/When-it-comes-to-losing-weight-which-is-more/

I say do it all. Yes you may be in the gym a bit longer doing weights also but extra calories burned is extra calories burned. I personally don't believe in any theory that says you will lose more by just one type of exercise or another. Calories consumed and burned is the only thing I believe in (unless so low on calories consumed your body goes into preservation mode).