Research from Australia has concluded that children who drink 2 cups of fruit juice or fruit drinks per day were more likely to be overweight or obese than those who did not.
It seems that the more fruit juice consumed, the more chance of being overweight:
"Children who drank more than three glasses of soft drink - three quarters of a litre or 750ml - or four glasses of fruit juice/drinks on the day in question were more than twice as likely to be overweight or obese compared with children who did not drink these drinks," (source)
This is a tough wake-up call for many parents. While carefully avoiding soft drinks, it's easy to stumble into the murky world of so-called "fruit" juices. Many of these juice brands proudly display "no added sugar" or "all-natural ingredients". However most are simply reconstituted juice and are basically just another form of sugar (fructose).
I believe it is unfair to come down hard on parents given the dubious marketing surrounding fruit juice. Soft drink vendors don't go around touting the health benefits of their drinks -- and yet fruit juice makers do.