Pediatrician said to start baby food for 4 month old baby?

My son is a bigger boy he's 4 months 3 days old and weighs 16 lbs 13 oz he was 8 lbs 13 oz at birth we went for his shots today and she said since he's bigger and drinks a ton of formula 4-6 oz per sitting that I should start him on vegetables everything I read it says 6 months should i go ahead and do it or wait? When did your child start baby food?