Some researchers looked at how long kids were breastfed and when baby foods were introduced and whether the kids were fat during childhood, adolescence, early adulthood, and age 42. The only relationship they found was that later introduction of baby food was related to being leaner at 42. "(F)or each month introduction of vegetables was delayed, the risk of being overweight at 42 ... was reduced by 10%."
That's a very large difference not to appear before middle age, so that makes it a little harder to accept. The study looked at 5068 kids in the Copenhagen Perinatal Cohort, a long-term prospective study in Denmark, the data are good. I wonder what's going on, but I'll wait to see it replicated before condemning baby food.