Lose Weight - Gain Muscle It Is A 2-Step Process
We'll start with losing weight (or rather, body fat), and why you should concentrate your efforts on this step first. By losing the extra body fat first (which is the "true goal" for weight loss), through healthy eating and moderate exercise, your muscles begin to build tone so that once you are ready to start the muscle-building phase your muscles are in a lot better shape for it. I read somewhere that losing weight is about creating a "calorie deficit" and I believe that's a good way to put it. In plain English, however, what it means is to lose fat, you need to burn off more calories than you take in each day.
How do you create a "calorie deficit?" You do it by manipulating and maintaining a low calorie diet and light to moderate exercise plan. Don't even think about trying those "fad/fast weight loss diets" either, because most of those are unhealthy and potentially harmful. Not to mention most people who use them and lose some pounds usually gain back what they lost and more. You want to create a long-term healthy eating and exercise plan so when the fat is gone, it doesn't come back! So now you know how to take care of step one of your plan to lose weight and gain muscle: create a "calorie deficit" to burn off the fat.
Step two is all about building muscle. How does one build muscle? You do it through strength and endurance training that focuses on working specific muscle groups in each training session.
Strength training generally involves the use of weights, but you will also want to do things like sit-ups, push-ups, pull-ups... and these training exercises can be done anywhere because the weight you'll be using is your own body weight! Still, free weights are going to come in handy for those other muscle-building reps you'll be doing, like squats, bench presses, and curls. For maximum effect and minimum possible damage, schedule your muscle-building workouts for 30 to 45 minutes a day, three days a week.
The main thing to remember when you start on your quest to lose weight and gain muscle is until excess body fat is gone, you'll just be gaining tone. After you've burned off the fat, then you'll be ready to build muscle mass, and your body will be in better condition for doing so if you concentrate on burning the fat first.