Favouring resistance training over general cardio has many benefits and is excellent for those wanting to get lean. Lifting weights builds muscle and the more muscle your body has then the more energy (calories) your body burns naturally by revving up your metabolism. Steady state cardio (aerobic exercise) can inhibit muscle building. Sticking to heavy resistance training (anaerobic exercise) is key if your goal is to burn fat. This is due to the recruitment of our bodies powerful type 2 muscle fibres.
EPOC, Excess Post Oxygen Consumption is the amount of energy burned post exercise and anaerobic exercise (sprints and lifting heavy loads) significantly elevates this, in some cases for up to 36 hours post exercise meaning your metabolism is significantly elevated. Therefore, if you train anaerobically often you already know the answer to what happens to your metabolism!!
Suggested at least 3 times per week to reap great benefits.