One of the common thread that ties weight loss exercises together is the use of compound exercises. Exercises have two basic categories: single-joint and multi- joint.
In a single joint exercise like a triceps extension, you engage only the muscles around that joint which in the case of your triceps are the muscles in the back of your arm connecting your shoulder to your elbow. The joint the moves is your elbow which makes a triceps extension a single joint exercise.
In a pushup on the other hand, you engage both your triceps and your pecs. The contractions happen at your elbow as well as your shoulder. Even if you disregarded all the other body parts that are engaged in a pushup, the fact that both your elbow and your shoulder joints are engaged, makes a pushup a multi- joint or a compound exercise.
Engaging large muscle groups like your chest and smaller muscle groups like your triceps in a compound exercise helps you burn more calories per repetition.
Weight loss programs like Venus Factor System should include compound exercise as part of their regiment.