Martina is right about solids being more for fun than as a significant nutrition source, and it certainly isn't going to be the "Magic bullet" for a hungry baby.
Also, with regards to the 6 month recommendation, there are other groups that say earlier is just fine. I believe the American Academy of Pediatrics (AAP) recommends somewhere between 4 and 6 months. Where in that time frame depends on the baby, and certainly a quick call to your doctor's office is warranted. I just tend to take the WHO recs with a grain of salt. They seem a bit overly cautious to me.