You seem quite aware of the various details regarding fitness training and it is good that you are asking to verify all that you read.Although the definite dividing lines are hard to differentiate (without laboratory equipment), the general rule is that, to mobilise fat stores as the primary source of energy, medium intensity aerobic workouts over periods of 15-50 minutes work well. The warm up period is important to soft-start the body into action and NOT to deplete the carbohydrate stores necessary for a full force energy store, required in the beginning of your workout.But the weight loss programmes for beginners tend to be different for those with more practice in training. Beginners tend to benefit from the above mentioned workout. Reaching a plateau after achieving moderate fitness levels will require you to bring in interval or versa training and other options to kick-start the body out of complacency. This is a specialised programme best done under supervision to cut the risk of injury and damage.