There are plenty of good bodyweight exercises that will build strength and endurance.
Pushups, close grip pushups, clap pushups, knuckle pushups, one-armed pushups, hindu pushups, handstand pressup, squats, burpees, bicycle kicks, pistol squats, well you get the idea. Just take the time to learn the more advanced and difficult versions of these exercises, it's fun and rewarding and then just do a lot of reps [img]/images/graemlins/smile.gif[/img].
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The single most important thing you can do to lose weight is count your calories at
www.fitday.com. Any type of cardio or weight training in addition to this is going to be beneficial.